CURRENT STATUS -------------- Lockdep tracks acquisition order of locks in order to detect deadlock, and IRQ and IRQ enable/disable state as well to take accident acquisitions into account.

Lockdep should be turned off once it detects and reports a deadlock since the data structure and algorithm are not reusable after detection because of the complex design.

PROBLEM ------- *Waits* and their *events* that never reach eventually cause deadlock. However, Lockdep is only interested in lock acquisition order, forcing to emulate lock acqusition even for just waits and events that have nothing to do with real lock.

Even worse, no one likes Lockdep's false positive detection because that prevents further one that might be more valuable. That's why all the kernel developers are sensitive to Lockdep's false positive.

Besides those, by tracking acquisition order, it cannot correctly deal with read lock and cross-event e.g. wait_for_completion()/complete() for deadlock detection. Lockdep is no longer a good tool for that purpose.

SOLUTION -------- Again, *waits* and their *events* that never reach eventually cause deadlock. The new solution, Dept(DEPendency Tracker), focuses on waits and events themselves. Dept tracks waits and events and report it if any event would be never reachable.

Dept does: . Works with read lock in the right way. . Works with any wait and event e.i. cross-event. . Continue to work even after reporting multiple times. . Provides simple and intuitive APIs. . Does exactly what dependency checker should do.

Q & A ----- Q. Is this the first try ever to address the problem? A. No. Cross-release feature (b09be676e0ff2 locking/lockdep: Implement the 'crossrelease' feature) addressed it 2 years ago that was a Lockdep extension and merged but reverted shortly because:

Cross-release started to report valuable hidden problems but started to give report false positive reports as well. For sure, no one likes Lockdep's false positive reports since it makes Lockdep stop, preventing reporting further real problems.

Q. Why not Dept was developed as an extension of Lockdep? A. Lockdep definitely includes all the efforts great developers have made for a long time so as to be quite stable enough. But I had to design and implement newly because of the following:

1) Lockdep was designed to track lock acquisition order. The APIs and implementation do not fit on wait-event model. 2) Lockdep is turned off on detection including false positive. Which is terrible and prevents developing any extension for stronger detection.

Q. Do you intend to totally replace Lockdep? A. No. Lockdep also checks if lock usage is correct. Of course, the dependency check routine should be replaced but the other functions should be still there.

Q. Do you mean the dependency check routine should be replaced right away? A. No. I admit Lockdep is stable enough thanks to great efforts kernel developers have made. Lockdep and Dept, both should be in the kernel until Dept gets considered stable.

Q. Stronger detection capability would give more false positive report. Which was a big problem when cross-release was introduced. Is it ok with Dept? A. It's ok. Dept allows multiple reporting thanks to simple and quite generalized design. Of course, false positive reports should be fixed anyway but it's no longer as a critical problem as it was.

Signed-off-by: Byungchul Park byungchul.park@lge.com --- include/linux/dept.h | 481 ++++++++ include/linux/dept_sdt.h | 62 + include/linux/hardirq.h | 3 + include/linux/irqflags.h | 33 +- include/linux/sched.h | 7 + init/init_task.c | 2 + init/main.c | 2 + kernel/Makefile | 1 + kernel/dependency/Makefile | 3 + kernel/dependency/dept.c | 2536 +++++++++++++++++++++++++++++++++++++++ kernel/dependency/dept_hash.h | 10 + kernel/dependency/dept_object.h | 13 + kernel/exit.c | 1 + kernel/fork.c | 2 + kernel/module.c | 2 + kernel/sched/core.c | 3 + kernel/softirq.c | 6 +- kernel/trace/trace_preemptirq.c | 19 +- lib/Kconfig.debug | 20 + 19 files changed, 3197 insertions(+), 9 deletions(-) create mode 100644 include/linux/dept.h create mode 100644 include/linux/dept_sdt.h create mode 100644 kernel/dependency/Makefile create mode 100644 kernel/dependency/dept.c create mode 100644 kernel/dependency/dept_hash.h create mode 100644 kernel/dependency/dept_object.h

diff --git a/include/linux/dept.h b/include/linux/dept.h new file mode 100644 index 0000000..c3fb3cf --- /dev/null +++ b/include/linux/dept.h @@ -0,0 +1,481 @@ +/* SPDX-License-Identifier: GPL-2.0 */ +/* + * DEPT(DEPendency Tracker) - runtime dependency tracker + * + * Started by Byungchul Park max.byungchul.park@gmail.com: + * + * Copyright (c) 2020 LG Electronics, Inc., Byungchul Park + */ + +#ifndef __LINUX_DEPT_H +#define __LINUX_DEPT_H + +#ifdef CONFIG_DEPT + +#include <linux/types.h> + +struct task_struct; + +#define DEPT_MAX_STACK_ENTRY 16 +#define DEPT_MAX_WAIT_HIST 64 +#define DEPT_MAX_ECXT_HELD 48 + +#define DEPT_MAX_SUBCLASSES 16 +#define DEPT_MAX_SUBCLASSES_EVT 2 +#define DEPT_MAX_SUBCLASSES_USR (DEPT_MAX_SUBCLASSES / DEPT_MAX_SUBCLASSES_EVT) +#define DEPT_MAX_SUBCLASSES_CACHE 2 + +#define DEPT_SIRQ 0 +#define DEPT_HIRQ 1 +#define DEPT_IRQS_NR 2 +#define DEPT_SIRQF (1UL << DEPT_SIRQ) +#define DEPT_HIRQF (1UL << DEPT_HIRQ) + +struct dept_ecxt; +struct dept_iecxt { + struct dept_ecxt *ecxt; + int enirq; + /* + * for preventing to add a new ecxt + */ + bool staled; +}; + +struct dept_wait; +struct dept_iwait { + struct dept_wait *wait; + int irq; + /* + * for preventing to add a new wait + */ + bool staled; + bool touched; +}; + +struct dept_class { + union { + struct llist_node pool_node; + + /* + * reference counter for object management + */ + atomic_t ref; + }; + + /* + * unique information about the class + */ + const char *name; + unsigned long key; + int sub; + + /* + * for BFS + */ + unsigned int bfs_gen; + int bfs_dist; + struct dept_class *bfs_parent; + + /* + * for hashing this object + */ + struct hlist_node hash_node; + + /* + * for linking all classes + */ + struct list_head all_node; + + /* + * for associating its dependencies + */ + struct list_head dep_head; + struct list_head dep_rev_head; + + /* + * for tracking IRQ dependencies + */ + struct dept_iecxt iecxt[DEPT_IRQS_NR]; + struct dept_iwait iwait[DEPT_IRQS_NR]; +}; + +struct dept_stack { + union { + struct llist_node pool_node; + + /* + * reference counter for object management + */ + atomic_t ref; + }; + + /* + * backtrace entries + */ + unsigned long raw[DEPT_MAX_STACK_ENTRY]; + int nr; +}; + +struct dept_ecxt { + union { + struct llist_node pool_node; + + /* + * reference counter for object management + */ + atomic_t ref; + }; + + /* + * function that entered to this ecxt + */ + const char *ecxt_fn; + + /* + * event function + */ + const char *event_fn; + + /* + * associated class + */ + struct dept_class *class; + + /* + * flag indicating which IRQ has been + * enabled within the event context + */ + unsigned long enirqf; + + /* + * where the IRQ-enabled happened + */ + unsigned long enirq_ip[DEPT_IRQS_NR]; + struct dept_stack *enirq_stack[DEPT_IRQS_NR]; + + /* + * where the event context started + */ + unsigned long ecxt_ip; + struct dept_stack *ecxt_stack; + + /* + * where the event triggered + */ + unsigned long event_ip; + struct dept_stack *event_stack; +}; + +struct dept_wait { + union { + struct llist_node pool_node; + + /* + * reference counter for object management + */ + atomic_t ref; + }; + + /* + * function causing this wait + */ + const char *wait_fn; + + /* + * the associated class + */ + struct dept_class *class; + + /* + * which IRQ the wait was placed in + */ + unsigned long irqf; + + /* + * where the IRQ wait happened + */ + unsigned long irq_ip[DEPT_IRQS_NR]; + struct dept_stack *irq_stack[DEPT_IRQS_NR]; + + /* + * where the wait happened + */ + unsigned long wait_ip; + struct dept_stack *wait_stack; +}; + +struct dept_dep { + union { + struct llist_node pool_node; + + /* + * reference counter for object management + */ + atomic_t ref; + }; + + /* + * key data of dependency + */ + struct dept_ecxt *ecxt; + struct dept_wait *wait; + + /* + * This object can be referred without dept_lock + * held but with IRQ disabled, e.g. for hash + * lookup. So deferred deletion is needed. + */ + struct rcu_head rh; + + /* + * for BFS + */ + struct list_head bfs_node; + + /* + * for hashing this object + */ + struct hlist_node hash_node; + + /* + * for linking to a class object + */ + struct list_head dep_node; + struct list_head dep_rev_node; +}; + +struct dept_hash { + /* + * hash table + */ + struct hlist_head *table; + + /* + * size of the table e.i. 2^bits + */ + int bits; +}; + +struct dept_pool { + const char *name; + + /* + * object size + */ + size_t obj_sz; + + /* + * the number of the static array + */ + atomic_t obj_nr; + + /* + * offset of ->pool_node + */ + size_t node_off; + + /* + * pointer to the pool + */ + void *spool; + struct llist_head boot_pool; + struct llist_head __percpu *lpool; +}; + +struct dept_ecxt_held { + /* + * associated event context + */ + struct dept_ecxt *ecxt; + + /* + * unique key for this dept_ecxt_held + */ + unsigned long key; + + /* + * the wgen when the event context started + */ + unsigned int wgen; + + /* + * for allowing user aware nesting + */ + int nest; +}; + +struct dept_wait_hist { + /* + * associated wait + */ + struct dept_wait *wait; + + /* + * unique id of all waits system-wise until wrapped + */ + unsigned int wgen; + + /* + * local context id to identify IRQ context + */ + unsigned int ctxt_id; +}; + +struct dept_key { + union { + /* + * Each byte-wise address will be used as its key. + */ + char subkeys[DEPT_MAX_SUBCLASSES]; + + /* + * for caching the main class pointer + */ + struct dept_class *classes[DEPT_MAX_SUBCLASSES_CACHE]; + }; +}; + +struct dept_map { + const char *name; + struct dept_key *keys; + int sub_usr; + + /* + * It's local copy for fast acces to the associated classes. And + * Also used for dept_key instance for statically defined map. + */ + struct dept_key keys_local; + + /* + * wait timestamp associated to this map + */ + unsigned int wgen; + + /* + * whether this map should be going to be checked or not + */ + bool nocheck; +}; + +struct dept_task { + /* + * all event contexts that have entered and before exiting + */ + struct dept_ecxt_held ecxt_held[DEPT_MAX_ECXT_HELD]; + int ecxt_held_pos; + + /* + * ring buffer holding all waits that have happened + */ + struct dept_wait_hist wait_hist[DEPT_MAX_WAIT_HIST]; + int wait_hist_pos; + + /* + * sequential id to identify each IRQ context + */ + unsigned int irq_id[DEPT_IRQS_NR]; + + /* + * for tracking IRQ-enabled points with cross-event + */ + unsigned int wgen_enirq[DEPT_IRQS_NR]; + + /* + * for keeping up-to-date IRQ-enabled points + */ + unsigned long enirq_ip[DEPT_IRQS_NR]; + + /* + * current effective IRQ-enabled flag + */ + unsigned long eff_enirqf; + + /* + * for reserving a current stack instance at each operation + */ + struct dept_stack *stack; + + /* + * for preventing recursive call into DEPT engine + */ + int recursive; + + /* + * for staging data to commit a wait + */ + struct dept_map *stage_m; + unsigned long stage_w_f; + const char *stage_w_fn; + int stage_ne; + + /* + * for tracking IRQ-enable state + */ + bool hardirqs_enabled; + bool softirqs_enabled; +}; + +#define DEPT_TASK_INITIALIZER(t) \ + .dept_task.wait_hist = { { .wait = NULL, } }, \ + .dept_task.ecxt_held_pos = 0, \ + .dept_task.wait_hist_pos = 0, \ + .dept_task.irq_id = { 0 }, \ + .dept_task.wgen_enirq = { 0 }, \ + .dept_task.enirq_ip = { 0 }, \ + .dept_task.recursive = 0, \ + .dept_task.hardirqs_enabled = false, \ + .dept_task.softirqs_enabled = false, + +extern void dept_on(void); +extern void dept_off(void); +extern void dept_init(void); +extern void dept_task_init(struct task_struct *t); +extern void dept_task_exit(struct task_struct *t); +extern void dept_free_range(void *start, unsigned int sz); +extern void dept_map_init(struct dept_map *m, struct dept_key *k, int sub, const char *n); +extern void dept_map_reinit(struct dept_map *m); +extern void dept_map_nocheck(struct dept_map *m); + +extern void dept_wait(struct dept_map *m, unsigned long w_f, unsigned long ip, const char *w_fn, int ne); +extern void dept_stage_wait(struct dept_map *m, unsigned long w_f, const char *w_fn, int ne); +extern void dept_ask_event_wait_commit(unsigned long ip); +extern void dept_clean_stage(void); +extern void dept_ecxt_enter(struct dept_map *m, unsigned long e_f, unsigned long ip, const char *c_fn, const char *e_fn, int ne); +extern void dept_ask_event(struct dept_map *m); +extern void dept_event(struct dept_map *m, unsigned long e_f, unsigned long ip, const char *e_fn); +extern void dept_ecxt_exit(struct dept_map *m, unsigned long ip); + +/* + * for users who want to manage external keys + */ +extern void dept_key_init(struct dept_key *k); +extern void dept_key_destroy(struct dept_key *k); +#else /* !CONFIG_DEPT */ +struct dept_key { }; +struct dept_map { }; +struct dept_task { }; + +#define DEPT_TASK_INITIALIZER(t) + +#define dept_on() do { } while (0) +#define dept_off() do { } while (0) +#define dept_init() do { } while (0) +#define dept_task_init(t) do { } while (0) +#define dept_task_exit(t) do { } while (0) +#define dept_free_range(s, sz) do { } while (0) +#define dept_map_init(m, k, s, n) do { (void)(n); (void)(k); } while (0) +#define dept_map_reinit(m) do { } while (0) +#define dept_map_nocheck(m) do { } while (0) + +#define dept_wait(m, w_f, ip, w_fn, ne) do { (void)(w_fn); } while (0) +#define dept_stage_wait(m, w_f, w_fn, ne) do { (void)(w_fn); } while (0) +#define dept_ask_event_wait_commit(ip) do { } while (0) +#define dept_clean_stage() do { } while (0) +#define dept_ecxt_enter(m, e_f, ip, c_fn, e_fn, ne) do { (void)(c_fn); (void)(e_fn); } while (0) +#define dept_ask_event(m) do { } while (0) +#define dept_event(m, e_f, ip, e_fn) do { (void)(e_fn); } while (0) +#define dept_ecxt_exit(m, ip) do { } while (0) +#define dept_key_init(k) do { (void)(k); } while (0) +#define dept_key_destroy(k) do { (void)(k); } while (0) +#endif +#endif /* __LINUX_DEPT_H */ diff --git a/include/linux/dept_sdt.h b/include/linux/dept_sdt.h new file mode 100644 index 0000000..375c4c3 --- /dev/null +++ b/include/linux/dept_sdt.h @@ -0,0 +1,62 @@ +/* SPDX-License-Identifier: GPL-2.0 */ +/* + * Dept Single-event Dependency Tracker + * + * Started by Byungchul Park max.byungchul.park@gmail.com: + * + * Copyright (c) 2020 LG Electronics, Inc., Byungchul Park + */ + +#ifndef __LINUX_DEPT_SDT_H +#define __LINUX_DEPT_SDT_H + +#include <linux/dept.h> + +#ifdef CONFIG_DEPT +#define DEPT_SDT_MAP_INIT(dname) { .name = #dname } + +/* + * SDT(Single-event Dependency Tracker) APIs + * + * In case that one dept_map instance maps to a single event, SDT APIs + * can be used. + */ +#define sdt_map_init(m) \ + do { \ + static struct dept_key __key; \ + dept_map_init(m, &__key, 0, #m); \ + } while (0) +#define sdt_map_init_key(m, k) dept_map_init(m, k, 0, #m) + +#define sdt_wait(m) \ + do { \ + dept_ask_event(m); \ + dept_wait(m, 1UL, _THIS_IP_, "wait", 0); \ + } while (0) +/* + * This will be committed in __schedule() when it actually gets to + * __schedule(). Both dept_ask_event() and dept_wait() will be performed + * on the commit in __schedule(). + */ +#define sdt_wait_prepare(m) dept_stage_wait(m, 1UL, "wait", 0) +#define sdt_wait_finish() dept_clean_stage() +#define sdt_ecxt_enter(m) dept_ecxt_enter(m, 1UL, _THIS_IP_, "start", "event", 0) +#define sdt_event(m) dept_event(m, 1UL, _THIS_IP_, "event") +#define sdt_ecxt_exit(m) dept_ecxt_exit(m, _THIS_IP_) +#else /* !CONFIG_DEPT */ +#define DEPT_SDT_MAP_INIT(dname) { } + +#define sdt_map_init(m) do { } while (0) +#define sdt_map_init_key(m, k) do { (void)(k); } while (0) +#define sdt_wait(m) do { } while (0) +#define sdt_wait_prepare(m) do { } while (0) +#define sdt_wait_finish() do { } while (0) +#define sdt_ecxt_enter(m) do { } while (0) +#define sdt_event(m) do { } while (0) +#define sdt_ecxt_exit(m) do { } while (0) +#endif + +#define DEFINE_DEPT_SDT(x) \ + struct dept_map x = DEPT_SDT_MAP_INIT(x) + +#endif /* __LINUX_DEPT_SDT_H */ diff --git a/include/linux/hardirq.h b/include/linux/hardirq.h index 76878b3..07005f2 100644 --- a/include/linux/hardirq.h +++ b/include/linux/hardirq.h @@ -5,6 +5,7 @@ #include <linux/context_tracking_state.h> #include <linux/preempt.h> #include <linux/lockdep.h> +#include <linux/dept.h> #include <linux/ftrace_irq.h> #include <linux/sched.h> #include <linux/vtime.h> @@ -114,6 +115,7 @@ static inline void rcu_nmi_exit(void) { } */ #define __nmi_enter() \ do { \ + dept_off(); \ lockdep_off(); \ arch_nmi_enter(); \ BUG_ON(in_nmi() == NMI_MASK); \ @@ -136,6 +138,7 @@ static inline void rcu_nmi_exit(void) { } __preempt_count_sub(NMI_OFFSET + HARDIRQ_OFFSET); \ arch_nmi_exit(); \ lockdep_on(); \ + dept_on(); \ } while (0)

#define nmi_exit() \ diff --git a/include/linux/irqflags.h b/include/linux/irqflags.h index 4b14093..6e7d7d2 100644 --- a/include/linux/irqflags.h +++ b/include/linux/irqflags.h @@ -31,6 +31,22 @@ static inline void lockdep_hardirqs_off(unsigned long ip) { } #endif

+#ifdef CONFIG_DEPT +extern void dept_hardirq_enter(void); +extern void dept_softirq_enter(void); +extern void dept_enable_hardirq(unsigned long ip); +extern void dept_enable_softirq(unsigned long ip); +extern void dept_disable_hardirq(unsigned long ip); +extern void dept_disable_softirq(unsigned long ip); +#else +static inline void dept_hardirq_enter(void) { } +static inline void dept_softirq_enter(void) { } +static inline void dept_enable_hardirq(unsigned long ip) { } +static inline void dept_enable_softirq(unsigned long ip) { } +static inline void dept_disable_hardirq(unsigned long ip) { } +static inline void dept_disable_softirq(unsigned long ip) { } +#endif + #ifdef CONFIG_TRACE_IRQFLAGS

/* Per-task IRQ trace events information. */ @@ -53,15 +69,19 @@ struct irqtrace_events { extern void trace_hardirqs_off_finish(void); extern void trace_hardirqs_on(void); extern void trace_hardirqs_off(void); +extern void trace_softirqs_on_caller(unsigned long ip); +extern void trace_softirqs_off_caller(unsigned long ip);

# define lockdep_hardirq_context() (raw_cpu_read(hardirq_context)) # define lockdep_softirq_context(p) ((p)->softirq_context) # define lockdep_hardirqs_enabled() (this_cpu_read(hardirqs_enabled)) # define lockdep_softirqs_enabled(p) ((p)->softirqs_enabled) -# define lockdep_hardirq_enter() \ -do { \ - if (__this_cpu_inc_return(hardirq_context) == 1)\ - current->hardirq_threaded = 0; \ +# define lockdep_hardirq_enter() \ +do { \ + if (__this_cpu_inc_return(hardirq_context) == 1) { \ + current->hardirq_threaded = 0; \ + dept_hardirq_enter(); \ + } \ } while (0) # define lockdep_hardirq_threaded() \ do { \ @@ -115,6 +135,8 @@ struct irqtrace_events { # define trace_hardirqs_off_finish() do { } while (0) # define trace_hardirqs_on() do { } while (0) # define trace_hardirqs_off() do { } while (0) +# define trace_softirqs_on_caller(ip) do { } while (0) +# define trace_softirqs_off_caller(ip) do { } while (0) # define lockdep_hardirq_context() 0 # define lockdep_softirq_context(p) 0 # define lockdep_hardirqs_enabled() 0 @@ -135,7 +157,8 @@ struct irqtrace_events { #if defined(CONFIG_TRACE_IRQFLAGS) && !defined(CONFIG_PREEMPT_RT) # define lockdep_softirq_enter() \ do { \ - current->softirq_context++; \ + if (!current->softirq_context++) \ + dept_softirq_enter(); \ } while (0) # define lockdep_softirq_exit() \ do { \ diff --git a/include/linux/sched.h b/include/linux/sched.h index 508b91d..1526b32 100644 --- a/include/linux/sched.h +++ b/include/linux/sched.h @@ -35,6 +35,7 @@ #include <linux/seqlock.h> #include <linux/kcsan.h> #include <asm/kmap_size.h> +#include <linux/dept.h>

/* task_struct member predeclarations (sorted alphabetically): */ struct audit_context; @@ -201,12 +202,16 @@ */ #define __set_current_state(state_value) \ do { \ + if (state_value == TASK_RUNNING) \ + dept_clean_stage(); \ debug_normal_state_change((state_value)); \ WRITE_ONCE(current->__state, (state_value)); \ } while (0)

#define set_current_state(state_value) \ do { \ + if (state_value == TASK_RUNNING) \ + dept_clean_stage(); \ debug_normal_state_change((state_value)); \ smp_store_mb(current->__state, (state_value)); \ } while (0) @@ -1157,6 +1162,8 @@ struct task_struct { struct held_lock held_locks[MAX_LOCK_DEPTH]; #endif

+ struct dept_task dept_task; + #if defined(CONFIG_UBSAN) && !defined(CONFIG_UBSAN_TRAP) unsigned int in_ubsan; #endif diff --git a/init/init_task.c b/init/init_task.c index 73cc8f0..d530256 100644 --- a/init/init_task.c +++ b/init/init_task.c @@ -12,6 +12,7 @@ #include <linux/audit.h> #include <linux/numa.h> #include <linux/scs.h> +#include <linux/dept.h>

#include <linux/uaccess.h>

@@ -193,6 +194,7 @@ struct task_struct init_task .curr_chain_key = INITIAL_CHAIN_KEY, .lockdep_recursion = 0, #endif + DEPT_TASK_INITIALIZER(init_task) #ifdef CONFIG_FUNCTION_GRAPH_TRACER .ret_stack = NULL, .tracing_graph_pause = ATOMIC_INIT(0), diff --git a/init/main.c b/init/main.c index 65fa2e4..ca96e11 100644 --- a/init/main.c +++ b/init/main.c @@ -65,6 +65,7 @@ #include <linux/debug_locks.h> #include <linux/debugobjects.h> #include <linux/lockdep.h> +#include <linux/dept.h> #include <linux/kmemleak.h> #include <linux/padata.h> #include <linux/pid_namespace.h> @@ -1070,6 +1071,7 @@ asmlinkage __visible void __init __no_sanitize_address start_kernel(void) panic_param);

lockdep_init(); + dept_init();

/* * Need to run this when irqs are enabled, because it wants diff --git a/kernel/Makefile b/kernel/Makefile index 56f4ee9..cef9b02 100644 --- a/kernel/Makefile +++ b/kernel/Makefile @@ -53,6 +53,7 @@ obj-y += rcu/ obj-y += livepatch/ obj-y += dma/ obj-y += entry/ +obj-y += dependency/

obj-$(CONFIG_KCMP) += kcmp.o obj-$(CONFIG_FREEZER) += freezer.o diff --git a/kernel/dependency/Makefile b/kernel/dependency/Makefile new file mode 100644 index 0000000..b5cfb8a --- /dev/null +++ b/kernel/dependency/Makefile @@ -0,0 +1,3 @@ +# SPDX-License-Identifier: GPL-2.0 + +obj-$(CONFIG_DEPT) += dept.o diff --git a/kernel/dependency/dept.c b/kernel/dependency/dept.c new file mode 100644 index 0000000..ec3f131 --- /dev/null +++ b/kernel/dependency/dept.c @@ -0,0 +1,2536 @@ +// SPDX-License-Identifier: GPL-2.0 +/* + * DEPT(DEPendency Tracker) - Runtime dependency tracker + * + * Started by Byungchul Park max.byungchul.park@gmail.com: + * + * Copyright (c) 2020 LG Electronics, Inc., Byungchul Park + * + * DEPT provides a general way to detect deadlock possibility in runtime + * and the interest is not limited to typical lock but to every + * syncronization primitives. + * + * The following ideas were borrowed from LOCKDEP: + * + * 1) Use a graph to track relationship between classes. + * 2) Prevent performance regression using hash. + * + * The following items were enhanced from LOCKDEP: + * + * 1) Cover more deadlock cases. + * 2) Allow muliple reports. + * + * TODO: Both LOCKDEP and DEPT should co-exist until DEPT is considered + * stable. Then the dependency check routine should be replaced with + * DEPT after. It should finally look like: + * + * + * + * As is: + * + * LOCKDEP + * +-----------------------------------------+ + * | Lock usage correctness check | <-> locks + * | | + * | | + * | +-------------------------------------+ | + * | | Dependency check | | + * | | (by tracking lock acquisition order)| | + * | +-------------------------------------+ | + * | | + * +-----------------------------------------+ + * + * DEPT + * +-----------------------------------------+ + * | Dependency check | <-> waits/events + * | (by tracking wait and event context) | + * +-----------------------------------------+ + * + * + * + * To be: + * + * LOCKDEP + * +-----------------------------------------+ + * | Lock usage correctness check | <-> locks + * | | + * | | + * | (Request dependency check) | + * | T | + * +--------------------|--------------------+ + * | + * DEPT V + * +-----------------------------------------+ + * | Dependency check | <-> waits/events + * | (by tracking wait and event context) | + * +-----------------------------------------+ + */ + +#include <linux/sched.h> +#include <linux/stacktrace.h> +#include <linux/spinlock.h> +#include <linux/kallsyms.h> +#include <linux/hash.h> +#include <linux/dept.h> +#include <linux/utsname.h> + +static int dept_stop; +static int dept_per_cpu_ready; + +#define DEPT_READY_WARN (!oops_in_progress) + +/* + * Make all operations using DEPT_WARN_ON() fail on oops_in_progress and + * prevent warning message. + */ +#define DEPT_WARN_ON_ONCE(c) \ + ({ \ + int __ret = 0; \ + \ + if (likely(DEPT_READY_WARN)) \ + __ret = WARN_ONCE(c, "DEPT_WARN_ON_ONCE: " #c); \ + __ret; \ + }) + +#define DEPT_WARN_ONCE(s...) \ + ({ \ + if (likely(DEPT_READY_WARN)) \ + WARN_ONCE(1, "DEPT_WARN_ONCE: " s); \ + }) + +#define DEPT_WARN_ON(c) \ + ({ \ + int __ret = 0; \ + \ + if (likely(DEPT_READY_WARN)) \ + __ret = WARN(c, "DEPT_WARN_ON: " #c); \ + __ret; \ + }) + +#define DEPT_WARN(s...) \ + ({ \ + if (likely(DEPT_READY_WARN)) \ + WARN(1, "DEPT_WARN: " s); \ + }) + +#define DEPT_STOP(s...) \ + ({ \ + WRITE_ONCE(dept_stop, 1); \ + if (likely(DEPT_READY_WARN)) \ + WARN(1, "DEPT_STOP: " s); \ + }) + +static arch_spinlock_t dept_spin = (arch_spinlock_t)__ARCH_SPIN_LOCK_UNLOCKED; + +/* + * DEPT internal engine should be careful in using outside functions + * e.g. printk at reporting since that kind of usage might cause + * untrackable deadlock. + */ +static atomic_t dept_outworld = ATOMIC_INIT(0); + +static inline void dept_outworld_enter(void) +{ + atomic_inc(&dept_outworld); +} + +static inline void dept_outworld_exit(void) +{ + atomic_dec(&dept_outworld); +} + +static inline bool dept_outworld_entered(void) +{ + return atomic_read(&dept_outworld); +} + +static inline bool dept_lock(void) +{ + while (!arch_spin_trylock(&dept_spin)) + if (unlikely(dept_outworld_entered())) + return false; + return true; +} + +static inline void dept_unlock(void) +{ + arch_spin_unlock(&dept_spin); +} + +/* + * whether to stack-trace on every wait or every ecxt + */ +static bool rich_stack = true; + +enum bfs_ret { + BFS_CONTINUE, + BFS_CONTINUE_REV, + BFS_DONE, + BFS_SKIP, +}; + +static inline bool before(unsigned int a, unsigned int b) +{ + return (int)(a - b) < 0; +} + +static inline bool valid_stack(struct dept_stack *s) +{ + return s && s->nr > 0; +} + +static inline bool valid_class(struct dept_class *c) +{ + return c->key; +} + +static inline void inval_class(struct dept_class *c) +{ + c->key = 0UL; +} + +static inline struct dept_ecxt *dep_e(struct dept_dep *d) +{ + return d->ecxt; +} + +static inline struct dept_wait *dep_w(struct dept_dep *d) +{ + return d->wait; +} + +static inline struct dept_class *dep_fc(struct dept_dep *d) +{ + return dep_e(d)->class; +} + +static inline struct dept_class *dep_tc(struct dept_dep *d) +{ + return dep_w(d)->class; +} + +static inline const char *irq_str(int irq) +{ + if (irq == DEPT_SIRQ) + return "softirq"; + if (irq == DEPT_HIRQ) + return "hardirq"; + return "(unknown)"; +} + +static inline struct dept_task *dept_task(void) +{ + return &current->dept_task; +} + +/* + * Pool + * ===================================================================== + * DEPT maintains pools to provide objects in a safe way. + * + * 1) Static pool is used at the beginning of booting time. + * 2) Local pool is tried first before the static pool. Objects that + * have been freed will be placed. + */ + +enum object_t { +#define OBJECT(id, nr) OBJECT_##id, + #include "dept_object.h" +#undef OBJECT + OBJECT_NR, +}; + +#define OBJECT(id, nr) \ +static struct dept_##id spool_##id[nr]; \ +static DEFINE_PER_CPU(struct llist_head, lpool_##id); + #include "dept_object.h" +#undef OBJECT + +static struct dept_pool pool[OBJECT_NR] = { +#define OBJECT(id, nr) { \ + .name = #id, \ + .obj_sz = sizeof(struct dept_##id), \ + .obj_nr = ATOMIC_INIT(nr), \ + .node_off = offsetof(struct dept_##id, pool_node), \ + .spool = spool_##id, \ + .lpool = &lpool_##id, }, + #include "dept_object.h" +#undef OBJECT +}; + +/* + * Can use llist no matter whether CONFIG_ARCH_HAVE_NMI_SAFE_CMPXCHG is + * enabled or not because NMI and other contexts in the same CPU never + * run inside of DEPT concurrently by preventing reentrance. + */ +static void *from_pool(enum object_t t) +{ + struct dept_pool *p; + struct llist_head *h; + struct llist_node *n; + + /* + * llist_del_first() doesn't allow concurrent access e.g. + * between process and IRQ context. + */ + if (DEPT_WARN_ON(!irqs_disabled())) + return NULL; + + p = &pool[t]; + + /* + * Try local pool first. + */ + if (likely(dept_per_cpu_ready)) + h = this_cpu_ptr(p->lpool); + else + h = &p->boot_pool; + + n = llist_del_first(h); + if (n) + return (void *)n - p->node_off; + + /* + * Try static pool. + */ + if (atomic_read(&p->obj_nr) > 0) { + int idx = atomic_dec_return(&p->obj_nr); + + if (idx >= 0) + return p->spool + (idx * p->obj_sz); + } + + DEPT_WARN_ONCE("Pool(%s) is empty.\n", p->name); + return NULL; +} + +static void to_pool(void *o, enum object_t t) +{ + struct dept_pool *p = &pool[t]; + struct llist_head *h; + + preempt_disable(); + if (likely(dept_per_cpu_ready)) + h = this_cpu_ptr(p->lpool); + else + h = &p->boot_pool; + + llist_add(o + p->node_off, h); + preempt_enable(); +} + +#define OBJECT(id, nr) \ +static void (*ctor_##id)(struct dept_##id *a); \ +static void (*dtor_##id)(struct dept_##id *a); \ +static inline struct dept_##id *new_##id(void) \ +{ \ + struct dept_##id *a; \ + \ + a = (struct dept_##id *)from_pool(OBJECT_##id); \ + if (unlikely(!a)) \ + return NULL; \ + \ + atomic_set(&a->ref, 1); \ + \ + if (ctor_##id) \ + ctor_##id(a); \ + \ + return a; \ +} \ + \ +static inline struct dept_##id *get_##id(struct dept_##id *a) \ +{ \ + atomic_inc(&a->ref); \ + return a; \ +} \ + \ +static inline void put_##id(struct dept_##id *a) \ +{ \ + if (!atomic_dec_return(&a->ref)) { \ + if (dtor_##id) \ + dtor_##id(a); \ + to_pool(a, OBJECT_##id); \ + } \ +} \ + \ +static inline void del_##id(struct dept_##id *a) \ +{ \ + put_##id(a); \ +} \ + \ +static inline bool id##_consumed(struct dept_##id *a) \ +{ \ + return a && atomic_read(&a->ref) > 1; \ +} +#include "dept_object.h" +#undef OBJECT + +#define SET_CONSTRUCTOR(id, f) \ +static void (*ctor_##id)(struct dept_##id *a) = f + +static void initialize_dep(struct dept_dep *d) +{ + INIT_LIST_HEAD(&d->bfs_node); + INIT_LIST_HEAD(&d->dep_node); + INIT_LIST_HEAD(&d->dep_rev_node); +} +SET_CONSTRUCTOR(dep, initialize_dep); + +static void initialize_class(struct dept_class *c) +{ + int i; + + for (i = 0; i < DEPT_IRQS_NR; i++) { + struct dept_iecxt *ie = &c->iecxt[i]; + struct dept_iwait *iw = &c->iwait[i]; + + ie->ecxt = NULL; + ie->enirq = i; + ie->staled = false; + + iw->wait = NULL; + iw->irq = i; + iw->staled = false; + iw->touched = false; + } + c->bfs_gen = 0U; + + INIT_LIST_HEAD(&c->all_node); + INIT_LIST_HEAD(&c->dep_head); + INIT_LIST_HEAD(&c->dep_rev_head); +} +SET_CONSTRUCTOR(class, initialize_class); + +static void initialize_ecxt(struct dept_ecxt *e) +{ + int i; + + for (i = 0; i < DEPT_IRQS_NR; i++) { + e->enirq_stack[i] = NULL; + e->enirq_ip[i] = 0UL; + } + e->ecxt_ip = 0UL; + e->ecxt_stack = NULL; + e->enirqf = 0UL; + e->event_stack = NULL; +} +SET_CONSTRUCTOR(ecxt, initialize_ecxt); + +static void initialize_wait(struct dept_wait *w) +{ + int i; + + for (i = 0; i < DEPT_IRQS_NR; i++) { + w->irq_stack[i] = NULL; + w->irq_ip[i] = 0UL; + } + w->wait_ip = 0UL; + w->wait_stack = NULL; + w->irqf = 0UL; +} +SET_CONSTRUCTOR(wait, initialize_wait); + +static void initialize_stack(struct dept_stack *s) +{ + s->nr = 0; +} +SET_CONSTRUCTOR(stack, initialize_stack); + +#define OBJECT(id, nr) \ +static void (*ctor_##id)(struct dept_##id *a); + #include "dept_object.h" +#undef OBJECT + +#undef SET_CONSTRUCTOR + +#define SET_DESTRUCTOR(id, f) \ +static void (*dtor_##id)(struct dept_##id *a) = f + +static void destroy_dep(struct dept_dep *d) +{ + if (dep_e(d)) + put_ecxt(dep_e(d)); + if (dep_w(d)) + put_wait(dep_w(d)); +} +SET_DESTRUCTOR(dep, destroy_dep); + +static void destroy_ecxt(struct dept_ecxt *e) +{ + int i; + + for (i = 0; i < DEPT_IRQS_NR; i++) + if (e->enirq_stack[i]) + put_stack(e->enirq_stack[i]); + if (e->class) + put_class(e->class); + if (e->ecxt_stack) + put_stack(e->ecxt_stack); + if (e->event_stack) + put_stack(e->event_stack); +} +SET_DESTRUCTOR(ecxt, destroy_ecxt); + +static void destroy_wait(struct dept_wait *w) +{ + int i; + + for (i = 0; i < DEPT_IRQS_NR; i++) + if (w->irq_stack[i]) + put_stack(w->irq_stack[i]); + if (w->class) + put_class(w->class); + if (w->wait_stack) + put_stack(w->wait_stack); +} +SET_DESTRUCTOR(wait, destroy_wait); + +#define OBJECT(id, nr) \ +static void (*dtor_##id)(struct dept_##id *a); + #include "dept_object.h" +#undef OBJECT + +#undef SET_DESTRUCTOR + +/* + * Caching and hashing + * ===================================================================== + * DEPT makes use of caching and hashing to improve performance. Each + * object can be obtained in O(1) with its key. + * + * NOTE: Currently we assume all the objects in the hashs will never be + * removed. Implement it when needed. + */ + +/* + * Some information might be lost but it's only for hashing key. + */ +static inline unsigned long mix(unsigned long a, unsigned long b) +{ + int halfbits = sizeof(unsigned long) * 8 / 2; + unsigned long halfmask = (1UL << halfbits) - 1UL; + + return (a << halfbits) | (b & halfmask); +} + +static bool cmp_dep(struct dept_dep *d1, struct dept_dep *d2) +{ + return dep_fc(d1)->key == dep_fc(d2)->key && + dep_tc(d1)->key == dep_tc(d2)->key; +} + +static unsigned long key_dep(struct dept_dep *d) +{ + return mix(dep_fc(d)->key, dep_tc(d)->key); +} + +static bool cmp_class(struct dept_class *c1, struct dept_class *c2) +{ + return c1->key == c2->key; +} + +static unsigned long key_class(struct dept_class *c) +{ + return c->key; +} + +#define HASH(id, bits) \ +static struct hlist_head table_##id[1UL << bits]; \ + \ +static inline struct hlist_head *head_##id(struct dept_##id *a) \ +{ \ + return table_##id + hash_long(key_##id(a), bits); \ +} \ + \ +static inline struct dept_##id *hash_lookup_##id(struct dept_##id *a) \ +{ \ + struct dept_##id *b; \ + \ + hlist_for_each_entry_rcu(b, head_##id(a), hash_node) \ + if (cmp_##id(a, b)) \ + return b; \ + return NULL; \ +} \ + \ +static inline void hash_add_##id(struct dept_##id *a) \ +{ \ + hlist_add_head_rcu(&a->hash_node, head_##id(a)); \ +} \ + \ +static inline void hash_del_##id(struct dept_##id *a) \ +{ \ + hlist_del_rcu(&a->hash_node); \ +} +#include "dept_hash.h" +#undef HASH + +static inline struct dept_dep *lookup_dep(struct dept_class *fc, + struct dept_class *tc) +{ + struct dept_ecxt onetime_e = { .class = fc }; + struct dept_wait onetime_w = { .class = tc }; + struct dept_dep onetime_d = { .ecxt = &onetime_e, + .wait = &onetime_w }; + return hash_lookup_dep(&onetime_d); +} + +static inline struct dept_class *lookup_class(unsigned long key) +{ + struct dept_class onetime_c = { .key = key }; + + return hash_lookup_class(&onetime_c); +} + +/* + * Report + * ===================================================================== + * DEPT prints useful information to help debuging on detection of + * problematic dependency. + */ + +static inline void print_ip_stack(unsigned long ip, struct dept_stack *s) +{ + if (ip) + print_ip_sym(KERN_WARNING, ip); + + if (valid_stack(s)) { + pr_warn("stacktrace:\n"); + stack_trace_print(s->raw, s->nr, 5); + } + + if (!ip && !valid_stack(s)) + pr_warn("(N/A)\n"); +} + +#define print_spc(spc, fmt, ...) \ + pr_warn("%*c" fmt, (spc) * 4, ' ', ##__VA_ARGS__) + +static void print_diagram(struct dept_dep *d) +{ + struct dept_ecxt *e = dep_e(d); + struct dept_wait *w = dep_w(d); + struct dept_class *fc = dep_fc(d); + struct dept_class *tc = dep_tc(d); + unsigned long irqf; + int irq; + bool firstline = true; + int spc = 1; + const char *w_fn = w->wait_fn ?: "(unknown)"; + const char *e_fn = e->event_fn ?: "(unknown)"; + const char *c_fn = e->ecxt_fn ?: "(unknown)"; + + irqf = e->enirqf & w->irqf; + for_each_set_bit(irq, &irqf, DEPT_IRQS_NR) { + if (!firstline) + pr_warn("\nor\n\n"); + firstline = false; + + print_spc(spc, "[S] %s(%s:%d)\n", c_fn, fc->name, fc->sub); + print_spc(spc, " <%s interrupt>\n", irq_str(irq)); + print_spc(spc + 1, "[W] %s(%s:%d)\n", w_fn, tc->name, tc->sub); + print_spc(spc, "[E] %s(%s:%d)\n", e_fn, fc->name, fc->sub); + } + + if (!irqf) { + print_spc(spc, "[S] %s(%s:%d)\n", c_fn, fc->name, fc->sub); + print_spc(spc, "[W] %s(%s:%d)\n", w_fn, tc->name, tc->sub); + print_spc(spc, "[E] %s(%s:%d)\n", e_fn, fc->name, fc->sub); + } +} + +static void print_dep(struct dept_dep *d) +{ + struct dept_ecxt *e = dep_e(d); + struct dept_wait *w = dep_w(d); + struct dept_class *fc = dep_fc(d); + struct dept_class *tc = dep_tc(d); + unsigned long irqf; + int irq; + const char *w_fn = w->wait_fn ?: "(unknown)"; + const char *e_fn = e->event_fn ?: "(unknown)"; + const char *c_fn = e->ecxt_fn ?: "(unknown)"; + + irqf = e->enirqf & w->irqf; + for_each_set_bit(irq, &irqf, DEPT_IRQS_NR) { + pr_warn("%s has been enabled:\n", irq_str(irq)); + print_ip_stack(e->enirq_ip[irq], e->enirq_stack[irq]); + pr_warn("\n"); + + pr_warn("[S] %s(%s:%d):\n", c_fn, fc->name, fc->sub); + print_ip_stack(e->ecxt_ip, e->ecxt_stack); + pr_warn("\n"); + + pr_warn("[W] %s(%s:%d) in %s context:\n", + w_fn, tc->name, tc->sub, irq_str(irq)); + print_ip_stack(w->irq_ip[irq], w->irq_stack[irq]); + pr_warn("\n"); + + pr_warn("[E] %s(%s:%d):\n", e_fn, fc->name, fc->sub); + print_ip_stack(e->event_ip, e->event_stack); + } + + if (!irqf) { + pr_warn("[S] %s(%s:%d):\n", c_fn, fc->name, fc->sub); + print_ip_stack(e->ecxt_ip, e->ecxt_stack); + pr_warn("\n"); + + pr_warn("[W] %s(%s:%d):\n", w_fn, tc->name, tc->sub); + print_ip_stack(w->wait_ip, w->wait_stack); + pr_warn("\n"); + + pr_warn("[E] %s(%s:%d):\n", e_fn, fc->name, fc->sub); + print_ip_stack(e->event_ip, e->event_stack); + } +} + +static void save_current_stack(int skip); + +/* + * Print all classes in a circle. + */ +static void print_circle(struct dept_class *c) +{ + struct dept_class *fc = c->bfs_parent; + struct dept_class *tc = c; + int i; + + dept_outworld_enter(); + save_current_stack(6); + + pr_warn("===================================================\n"); + pr_warn("DEPT: Circular dependency has been detected.\n"); + pr_warn("%s %.*s %s\n", init_utsname()->release, + (int)strcspn(init_utsname()->version, " "), + init_utsname()->version, + print_tainted()); + pr_warn("---------------------------------------------------\n"); + pr_warn("summary\n"); + pr_warn("---------------------------------------------------\n"); + + if (fc == tc) + pr_warn("*** AA DEADLOCK ***\n\n"); + else + pr_warn("*** DEADLOCK ***\n\n"); + + i = 0; + do { + struct dept_dep *d = lookup_dep(fc, tc); + + pr_warn("context %c\n", 'A' + (i++)); + print_diagram(d); + if (fc != c) + pr_warn("\n"); + + tc = fc; + fc = fc->bfs_parent; + } while (tc != c); + + pr_warn("\n"); + pr_warn("[S]: start of the event context\n"); + pr_warn("[W]: the wait blocked\n"); + pr_warn("[E]: the event not reachable\n"); + + i = 0; + do { + struct dept_dep *d = lookup_dep(fc, tc); + + pr_warn("---------------------------------------------------\n"); + pr_warn("context %c's detail\n", 'A' + i); + pr_warn("---------------------------------------------------\n"); + pr_warn("context %c\n", 'A' + (i++)); + print_diagram(d); + pr_warn("\n"); + print_dep(d); + + tc = fc; + fc = fc->bfs_parent; + } while (tc != c); + + pr_warn("---------------------------------------------------\n"); + pr_warn("information that might be helpful\n"); + pr_warn("---------------------------------------------------\n"); + dump_stack(); + + dept_outworld_exit(); +} + +/* + * BFS(Breadth First Search) + * ===================================================================== + * Whenever a new dependency is added into the graph, search the graph + * for a new circular dependency. + */ + +static inline void enqueue(struct list_head *h, struct dept_dep *d) +{ + list_add_tail(&d->bfs_node, h); +} + +static inline struct dept_dep *dequeue(struct list_head *h) +{ + struct dept_dep *d; + + d = list_first_entry(h, struct dept_dep, bfs_node); + list_del(&d->bfs_node); + return d; +} + +static inline bool empty(struct list_head *h) +{ + return list_empty(h); +} + +static void extend_queue(struct list_head *h, struct dept_class *cur) +{ + struct dept_dep *d; + + list_for_each_entry(d, &cur->dep_head, dep_node) { + struct dept_class *next = dep_tc(d); + + if (cur->bfs_gen == next->bfs_gen) + continue; + next->bfs_gen = cur->bfs_gen; + next->bfs_dist = cur->bfs_dist + 1; + next->bfs_parent = cur; + enqueue(h, d); + } +} + +static void extend_queue_rev(struct list_head *h, struct dept_class *cur) +{ + struct dept_dep *d; + + list_for_each_entry(d, &cur->dep_rev_head, dep_rev_node) { + struct dept_class *next = dep_fc(d); + + if (cur->bfs_gen == next->bfs_gen) + continue; + next->bfs_gen = cur->bfs_gen; + next->bfs_dist = cur->bfs_dist + 1; + next->bfs_parent = cur; + enqueue(h, d); + } +} + +typedef enum bfs_ret bfs_f(struct dept_dep *d, void *in, void **out); +static unsigned int bfs_gen; + +/* + * NOTE: Must be called with dept_lock held. + */ +static void bfs(struct dept_class *c, bfs_f *cb, void *in, void **out) +{ + LIST_HEAD(q); + enum bfs_ret ret; + + if (DEPT_WARN_ON(!cb)) + return; + + /* + * Avoid zero bfs_gen. + */ + bfs_gen = bfs_gen + 1 ?: 1; + + c->bfs_gen = bfs_gen; + c->bfs_dist = 0; + c->bfs_parent = c; + + ret = cb(NULL, in, out); + if (ret == BFS_DONE) + return; + if (ret == BFS_SKIP) + return; + if (ret == BFS_CONTINUE) + extend_queue(&q, c); + if (ret == BFS_CONTINUE_REV) + extend_queue_rev(&q, c); + + while (!empty(&q)) { + struct dept_dep *d = dequeue(&q); + + ret = cb(d, in, out); + if (ret == BFS_DONE) + break; + if (ret == BFS_SKIP) + continue; + if (ret == BFS_CONTINUE) + extend_queue(&q, dep_tc(d)); + if (ret == BFS_CONTINUE_REV) + extend_queue_rev(&q, dep_fc(d)); + } + + while (!empty(&q)) + dequeue(&q); +} + +/* + * Main operations + * ===================================================================== + * Add dependencies - Each new dependency is added into the graph and + * checked if it forms a circular dependency. + * + * Track waits - Waits are queued into the ring buffer for later use to + * generate appropriate dependencies with cross-event. + * + * Track event contexts(ecxt) - Event contexts are pushed into local + * stack for later use to generate appropriate dependencies with waits. + */ + +static inline unsigned long cur_enirqf(void); +static inline int cur_irq(void); +static inline unsigned int cur_ctxt_id(void); + +static inline struct dept_iecxt *iecxt(struct dept_class *c, int irq) +{ + return &c->iecxt[irq]; +} + +static inline struct dept_iwait *iwait(struct dept_class *c, int irq) +{ + return &c->iwait[irq]; +} + +static inline void stale_iecxt(struct dept_iecxt *ie) +{ + if (ie->ecxt) + put_ecxt(ie->ecxt); + + WRITE_ONCE(ie->ecxt, NULL); + WRITE_ONCE(ie->staled, true); +} + +static inline void set_iecxt(struct dept_iecxt *ie, struct dept_ecxt *e) +{ + /* + * ->ecxt will never be updated once getting set until the class + * gets removed. + */ + if (ie->ecxt) + DEPT_WARN_ON(1); + else + WRITE_ONCE(ie->ecxt, get_ecxt(e)); +} + +static inline void stale_iwait(struct dept_iwait *iw) +{ + if (iw->wait) + put_wait(iw->wait); + + WRITE_ONCE(iw->wait, NULL); + WRITE_ONCE(iw->staled, true); +} + +static inline void set_iwait(struct dept_iwait *iw, struct dept_wait *w) +{ + /* + * ->wait will never be updated once getting set until the class + * gets removed. + */ + if (iw->wait) + DEPT_WARN_ON(1); + else + WRITE_ONCE(iw->wait, get_wait(w)); + + iw->touched = true; +} + +static inline void touch_iwait(struct dept_iwait *iw) +{ + iw->touched = true; +} + +static inline void untouch_iwait(struct dept_iwait *iw) +{ + iw->touched = false; +} + +static inline struct dept_stack *get_current_stack(void) +{ + struct dept_stack *s = dept_task()->stack; + + return s ? get_stack(s) : NULL; +} + +static inline void prepare_current_stack(void) +{ + struct dept_stack *s = dept_task()->stack; + + /* + * The dept_stack is already ready. + */ + if (s && !stack_consumed(s)) { + s->nr = 0; + return; + } + + if (s) + put_stack(s); + + s = dept_task()->stack = new_stack(); + if (!s) + return; + + get_stack(s); + del_stack(s); +} + +static void save_current_stack(int skip) +{ + struct dept_stack *s = dept_task()->stack; + + if (!s) + return; + if (valid_stack(s)) + return; + + s->nr = stack_trace_save(s->raw, DEPT_MAX_STACK_ENTRY, skip); +} + +static void finish_current_stack(void) +{ + struct dept_stack *s = dept_task()->stack; + + if (stack_consumed(s)) + save_current_stack(2); +} + +/* + * FIXME: For now, disable LOCKDEP while DEPT is working. + * + * Both LOCKDEP and DEPT report it on a deadlock detection using + * printk taking the risk of another deadlock that might be caused by + * locks of console or printk between inside and outside of them. + * + * For DEPT, it's no problem since multiple reports are allowed. But it + * would be a bad idea for LOCKDEP since it will stop even on a singe + * report. So we need to prevent LOCKDEP from its reporting the risk + * DEPT would take when reporting something. + */ +#include <linux/lockdep.h> + +void dept_off(void) +{ + dept_task()->recursive++; + lockdep_off(); +} + +void dept_on(void) +{ + dept_task()->recursive--; + lockdep_on(); +} + +static inline unsigned long dept_enter(void) +{ + unsigned long flags; + + raw_local_irq_save(flags); + dept_off(); + prepare_current_stack(); + return flags; +} + +static inline void dept_exit(unsigned long flags) +{ + finish_current_stack(); + dept_on(); + raw_local_irq_restore(flags); +} + +/* + * NOTE: Must be called with dept_lock held. + */ +static struct dept_dep *__add_dep(struct dept_ecxt *e, + struct dept_wait *w) +{ + struct dept_dep *d; + + if (!valid_class(e->class) || !valid_class(w->class)) + return NULL; + + if (lookup_dep(e->class, w->class)) + return NULL; + + d = new_dep(); + if (unlikely(!d)) + return NULL; + + d->ecxt = get_ecxt(e); + d->wait = get_wait(w); + + /* + * Add the dependency into hash and graph. + */ + hash_add_dep(d); + list_add(&d->dep_node, &dep_fc(d)->dep_head); + list_add(&d->dep_rev_node, &dep_tc(d)->dep_rev_head); + return d; +} + +static enum bfs_ret cb_check_dl(struct dept_dep *d, + void *in, void **out) +{ + struct dept_dep *new = (struct dept_dep *)in; + + /* + * initial condition for this BFS search + */ + if (!d) { + dep_tc(new)->bfs_parent = dep_fc(new); + + if (dep_tc(new) != dep_fc(new)) + return BFS_CONTINUE; + + /* + * AA circle does not make additional deadlock. We don't + * have to continue this BFS search. + */ + print_circle(dep_tc(new)); + return BFS_DONE; + } + + /* + * Allow multiple reports. + */ + if (dep_tc(d) == dep_fc(new)) + print_circle(dep_tc(new)); + + return BFS_CONTINUE; +} + +/* + * This function is actually in charge of reporting. + */ +static inline void check_dl_bfs(struct dept_dep *d) +{ + bfs(dep_tc(d), cb_check_dl, (void *)d, NULL); +} + +static enum bfs_ret cb_find_iw(struct dept_dep *d, void *in, void **out) +{ + int irq = *(int *)in; + struct dept_class *fc; + struct dept_iwait *iw; + + if (DEPT_WARN_ON(!out)) + return BFS_DONE; + + /* + * initial condition for this BFS search + */ + if (!d) + return BFS_CONTINUE_REV; + + fc = dep_fc(d); + iw = iwait(fc, irq); + + /* + * If any parent's ->wait was set, then the children would've + * been touched. + */ + if (!iw->touched) + return BFS_SKIP; + + if (!iw->wait) + return BFS_CONTINUE_REV; + + *out = iw; + return BFS_DONE; +} + +static struct dept_iwait *find_iw_bfs(struct dept_class *c, int irq) +{ + struct dept_iwait *iw = iwait(c, irq); + struct dept_iwait *found = NULL; + + if (iw->wait) + return iw; + + /* + * '->touched == false' guarantees there's no parent that has + * been set ->wait. + */ + if (!iw->touched) + return NULL; + + bfs(c, cb_find_iw, (void *)&irq, (void **)&found); + + if (found) + return found; + + untouch_iwait(iw); + return NULL; +} + +static enum bfs_ret cb_touch_iw_find_ie(struct dept_dep *d, void *in, + void **out) +{ + int irq = *(int *)in; + struct dept_class *tc; + struct dept_iecxt *ie; + struct dept_iwait *iw; + + if (DEPT_WARN_ON(!out)) + return BFS_DONE; + + /* + * initial condition for this BFS search + */ + if (!d) + return BFS_CONTINUE; + + tc = dep_tc(d); + ie = iecxt(tc, irq); + iw = iwait(tc, irq); + + touch_iwait(iw); + + if (!ie->ecxt) + return BFS_CONTINUE; + + if (!*out) + *out = ie; + + return BFS_CONTINUE; +} + +static struct dept_iecxt *touch_iw_find_ie_bfs(struct dept_class *c, + int irq) +{ + struct dept_iecxt *ie = iecxt(c, irq); + struct dept_iwait *iw = iwait(c, irq); + struct dept_iecxt *found = ie->ecxt ? ie : NULL; + + touch_iwait(iw); + bfs(c, cb_touch_iw_find_ie, (void *)&irq, (void **)&found); + return found; +} + +/* + * Should be called with dept_lock held. + */ +static void __add_idep(struct dept_iecxt *ie, struct dept_iwait *iw) +{ + struct dept_dep *new; + + /* + * There's nothing to do. + */ + if (!ie || !iw || !ie->ecxt || !iw->wait) + return; + + new = __add_dep(ie->ecxt, iw->wait); + + /* + * Deadlock detected. Let check_dl_bfs() report it. + */ + if (new) { + check_dl_bfs(new); + stale_iecxt(ie); + stale_iwait(iw); + } + + /* + * If !new, it would be the case of lack of object resource. + * Just let it go and get checked by other chances. Retrying is + * meaningless in that case. + */ +} + +static void set_check_iecxt(struct dept_class *c, int irq, + struct dept_ecxt *e) +{ + struct dept_iecxt *ie = iecxt(c, irq); + + set_iecxt(ie, e); + __add_idep(ie, find_iw_bfs(c, irq)); +} + +static void set_check_iwait(struct dept_class *c, int irq, + struct dept_wait *w) +{ + struct dept_iwait *iw = iwait(c, irq); + + set_iwait(iw, w); + __add_idep(touch_iw_find_ie_bfs(c, irq), iw); +} + +static void add_iecxt(struct dept_class *c, int irq, struct dept_ecxt *e, + bool stack) +{ + /* + * This access is safe since we ensure e->class has set locally. + */ + struct dept_task *dt = dept_task(); + struct dept_iecxt *ie = iecxt(c, irq); + + if (unlikely(READ_ONCE(ie->staled))) + return; + + /* + * Skip add_iecxt() if ie->ecxt has ever been set at least once. + * Which means it has a valid ->ecxt or been staled. + */ + if (READ_ONCE(ie->ecxt)) + return; + + if (unlikely(!dept_lock())) + return; + + if (unlikely(ie->staled)) + goto unlock; + if (ie->ecxt) + goto unlock; + + e->enirqf |= (1UL << irq); + + /* + * Should be NULL since it's the first time that these + * enirq_{ip,stack}[irq] have ever set. + */ + DEPT_WARN_ON(e->enirq_ip[irq]); + DEPT_WARN_ON(e->enirq_stack[irq]); + + e->enirq_ip[irq] = dt->enirq_ip[irq]; + e->enirq_stack[irq] = stack ? get_current_stack() : NULL; + + set_check_iecxt(c, irq, e); +unlock: + dept_unlock(); +} + +static void add_iwait(struct dept_class *c, int irq, struct dept_wait *w) +{ + struct dept_iwait *iw = iwait(c, irq); + + if (unlikely(READ_ONCE(iw->staled))) + return; + + /* + * Skip add_iwait() if iw->wait has ever been set at least once. + * Which means it has a valid ->wait or been staled. + */ + if (READ_ONCE(iw->wait)) + return; + + if (unlikely(!dept_lock())) + return; + + if (unlikely(iw->staled)) + goto unlock; + if (iw->wait) + goto unlock; + + w->irqf |= (1UL << irq); + + /* + * Should be NULL since it's the first time that these + * irq_{ip,stack}[irq] have ever set. + */ + DEPT_WARN_ON(w->irq_ip[irq]); + DEPT_WARN_ON(w->irq_stack[irq]); + + w->irq_ip[irq] = w->wait_ip; + w->irq_stack[irq] = get_current_stack(); + + set_check_iwait(c, irq, w); +unlock: + dept_unlock(); +} + +static inline struct dept_wait_hist *hist(int pos) +{ + struct dept_task *dt = dept_task(); + + return dt->wait_hist + (pos % DEPT_MAX_WAIT_HIST); +} + +static inline int hist_pos_next(void) +{ + struct dept_task *dt = dept_task(); + + return dt->wait_hist_pos % DEPT_MAX_WAIT_HIST; +} + +static inline void hist_advance(void) +{ + struct dept_task *dt = dept_task(); + + dt->wait_hist_pos++; + dt->wait_hist_pos %= DEPT_MAX_WAIT_HIST; +} + +static inline struct dept_wait_hist *new_hist(void) +{ + struct dept_wait_hist *wh = hist(hist_pos_next()); + + hist_advance(); + return wh; +} + +static void add_hist(struct dept_wait *w, unsigned int wg, unsigned int ctxt_id) +{ + struct dept_wait_hist *wh = new_hist(); + + if (likely(wh->wait)) + put_wait(wh->wait); + + wh->wait = get_wait(w); + wh->wgen = wg; + wh->ctxt_id = ctxt_id; +} + +/* + * Should be called after setting up e's iecxt and w's iwait. + */ +static void add_dep(struct dept_ecxt *e, struct dept_wait *w) +{ + struct dept_class *fc = e->class; + struct dept_class *tc = w->class; + struct dept_dep *d; + int i; + + if (lookup_dep(fc, tc)) + return; + + if (unlikely(!dept_lock())) + return; + + /* + * __add_dep() will lookup_dep() again with lock held. + */ + d = __add_dep(e, w); + if (d) { + check_dl_bfs(d); + + for (i = 0; i < DEPT_IRQS_NR; i++) { + struct dept_iwait *fiw = iwait(fc, i); + struct dept_iecxt *found_ie; + struct dept_iwait *found_iw; + + /* + * '->touched == false' guarantees there's no + * parent that has been set ->wait. + */ + if (!fiw->touched) + continue; + + /* + * find_iw_bfs() will untouch the iwait if + * not found. + */ + found_iw = find_iw_bfs(fc, i); + + if (!found_iw) + continue; + + found_ie = touch_iw_find_ie_bfs(tc, i); + __add_idep(found_ie, found_iw); + } + } + dept_unlock(); +} + +static atomic_t wgen = ATOMIC_INIT(1); + +static void add_wait(struct dept_class *c, unsigned long ip, + const char *w_fn, int ne) +{ + struct dept_task *dt = dept_task(); + struct dept_wait *w; + unsigned int wg = 0U; + int irq; + int i; + + w = new_wait(); + if (unlikely(!w)) + return; + + WRITE_ONCE(w->class, get_class(c)); + w->wait_ip = ip; + w->wait_fn = w_fn; + w->wait_stack = get_current_stack(); + + irq = cur_irq(); + if (irq < DEPT_IRQS_NR) + add_iwait(c, irq, w); + + /* + * Avoid adding dependency between user aware nested ecxt and + * wait. + */ + for (i = dt->ecxt_held_pos - 1; i >= 0; i--) { + struct dept_ecxt_held *eh; + + eh = dt->ecxt_held + i; + if (eh->ecxt->class != c || eh->nest == ne) + break; + } + + for (; i >= 0; i--) { + struct dept_ecxt_held *eh; + + eh = dt->ecxt_held + i; + add_dep(eh->ecxt, w); + } + + if (!wait_consumed(w) && !rich_stack) { + if (w->wait_stack) + put_stack(w->wait_stack); + w->wait_stack = NULL; + } + + /* + * Avoid zero wgen. + */ + wg = atomic_inc_return(&wgen) ?: atomic_inc_return(&wgen); + add_hist(w, wg, cur_ctxt_id()); + + del_wait(w); +} + +static void add_ecxt(void *obj, struct dept_class *c, unsigned long ip, + const char *c_fn, const char *e_fn, int ne) +{ + struct dept_task *dt = dept_task(); + struct dept_ecxt_held *eh; + struct dept_ecxt *e; + unsigned long irqf; + int irq; + + if (DEPT_WARN_ON(dt->ecxt_held_pos == DEPT_MAX_ECXT_HELD)) + return; + + e = new_ecxt(); + if (unlikely(!e)) + return; + + e->class = get_class(c); + e->ecxt_ip = ip; + e->ecxt_stack = ip && rich_stack ? get_current_stack() : NULL; + e->event_fn = e_fn; + e->ecxt_fn = c_fn; + + eh = dt->ecxt_held + (dt->ecxt_held_pos++); + eh->ecxt = get_ecxt(e); + eh->key = (unsigned long)obj; + eh->wgen = atomic_read(&wgen); + eh->nest = ne; + + irqf = cur_enirqf(); + for_each_set_bit(irq, &irqf, DEPT_IRQS_NR) + add_iecxt(c, irq, e, false); + + del_ecxt(e); +} + +static int find_ecxt_pos(unsigned long key, bool newfirst) +{ + struct dept_task *dt = dept_task(); + int i; + + if (newfirst) { + for (i = dt->ecxt_held_pos - 1; i >= 0; i--) + if (dt->ecxt_held[i].key == key) + return i; + } else { + for (i = 0; i < dt->ecxt_held_pos; i++) + if (dt->ecxt_held[i].key == key) + return i; + } + return -1; +} + +static void pop_ecxt(void *obj) +{ + struct dept_task *dt = dept_task(); + unsigned long key = (unsigned long)obj; + int pos; + int i; + + /* + * TODO: Warn on pos == -1. + */ + pos = find_ecxt_pos(key, true); + if (pos == -1) + return; + + put_ecxt(dt->ecxt_held[pos].ecxt); + dt->ecxt_held_pos--; + + for (i = pos; i < dt->ecxt_held_pos; i++) + dt->ecxt_held[i] = dt->ecxt_held[i + 1]; +} + +static inline bool good_hist(struct dept_wait_hist *wh, unsigned int wg) +{ + return wh->wait != NULL && before(wg, wh->wgen); +} + +/* + * Binary-search the ring buffer for the earliest valid wait. + */ +static int find_hist_pos(unsigned int wg) +{ + int oldest; + int l; + int r; + int pos; + + oldest = hist_pos_next(); + if (unlikely(good_hist(hist(oldest), wg))) { + DEPT_WARN_ONCE("Need to expand the ring buffer.\n"); + return oldest; + } + + l = oldest + 1; + r = oldest + DEPT_MAX_WAIT_HIST - 1; + for (pos = (l + r) / 2; l <= r; pos = (l + r) / 2) { + struct dept_wait_hist *p = hist(pos - 1); + struct dept_wait_hist *wh = hist(pos); + + if (!good_hist(p, wg) && good_hist(wh, wg)) + return pos % DEPT_MAX_WAIT_HIST; + if (good_hist(wh, wg)) + r = pos - 1; + else + l = pos + 1; + } + return -1; +} + +static void do_event(void *obj, struct dept_class *c, unsigned int wg, + unsigned long ip) +{ + struct dept_task *dt = dept_task(); + struct dept_wait_hist *wh; + struct dept_ecxt_held *eh; + unsigned long key = (unsigned long)obj; + unsigned int ctxt_id; + int end; + int pos; + int i; + + /* + * The event was triggered before wait. + */ + if (!wg) + return; + + pos = find_ecxt_pos(key, false); + if (pos == -1) + return; + + eh = dt->ecxt_held + pos; + eh->ecxt->event_ip = ip; + eh->ecxt->event_stack = get_current_stack(); + + /* + * The ecxt already has done what it needs. + */ + if (!before(wg, eh->wgen)) + return; + + pos = find_hist_pos(wg); + if (pos == -1) + return; + + ctxt_id = cur_ctxt_id(); + end = hist_pos_next(); + end = end > pos ? end : end + DEPT_MAX_WAIT_HIST; + for (wh = hist(pos); pos < end; wh = hist(++pos)) { + if (wh->ctxt_id == ctxt_id) + add_dep(eh->ecxt, wh->wait); + if (!before(wh->wgen, eh->wgen)) + break; + } + + for (i = 0; i < DEPT_IRQS_NR; i++) { + struct dept_ecxt *e; + + if (before(dt->wgen_enirq[i], wg)) + continue; + + e = eh->ecxt; + add_iecxt(e->class, i, e, false); + } +} + +static void del_dep_rcu(struct rcu_head *rh) +{ + struct dept_dep *d = container_of(rh, struct dept_dep, rh); + + preempt_disable(); + del_dep(d); + preempt_enable(); +} + +/* + * NOTE: Must be called with dept_lock held. + */ +static void disconnect_class(struct dept_class *c) +{ + struct dept_dep *d, *n; + int i; + + list_for_each_entry_safe(d, n, &c->dep_head, dep_node) { + list_del_rcu(&d->dep_node); + list_del_rcu(&d->dep_rev_node); + hash_del_dep(d); + call_rcu(&d->rh, del_dep_rcu); + } + + list_for_each_entry_safe(d, n, &c->dep_rev_head, dep_rev_node) { + list_del_rcu(&d->dep_node); + list_del_rcu(&d->dep_rev_node); + hash_del_dep(d); + call_rcu(&d->rh, del_dep_rcu); + } + + for (i = 0; i < DEPT_IRQS_NR; i++) { + stale_iecxt(iecxt(c, i)); + stale_iwait(iwait(c, i)); + } +} + +/* + * IRQ context control + * ===================================================================== + * Whether a wait is in {hard,soft}-IRQ context or whether + * {hard,soft}-IRQ has been enabled on the way to an event is very + * important to check dependency. All those things should be tracked. + */ + +static inline unsigned long cur_enirqf(void) +{ + struct dept_task *dt = dept_task(); + int he = dt->hardirqs_enabled; + int se = dt->softirqs_enabled; + + if (he) + return DEPT_HIRQF | (se ? DEPT_SIRQF : 0UL); + return 0UL; +} + +static inline int cur_irq(void) +{ + if (lockdep_softirq_context(current)) + return DEPT_SIRQ; + if (lockdep_hardirq_context()) + return DEPT_HIRQ; + return DEPT_IRQS_NR; +} + +static inline unsigned int cur_ctxt_id(void) +{ + struct dept_task *dt = dept_task(); + int irq = cur_irq(); + + /* + * Normal process context + */ + if (irq == DEPT_IRQS_NR) + return 0U; + + return dt->irq_id[irq] | (1UL << irq); +} + +static void enirq_transition(int irq) +{ + struct dept_task *dt = dept_task(); + int i; + + /* + * READ wgen >= wgen of an event with IRQ enabled has been + * observed on the way to the event means, the IRQ can cut in + * within the ecxt. Used for cross-event detection. + * + * wait context event context(ecxt) + * ------------ ------------------- + * wait event + * WRITE wgen + * observe IRQ enabled + * READ wgen + * keep the wgen locally + * + * on the event + * check the local wgen + */ + dt->wgen_enirq[irq] = atomic_read(&wgen); + + for (i = dt->ecxt_held_pos - 1; i >= 0; i--) { + struct dept_ecxt_held *eh; + struct dept_ecxt *e; + + eh = dt->ecxt_held + i; + e = eh->ecxt; + add_iecxt(e->class, irq, e, true); + } +} + +static void enirq_update(unsigned long ip) +{ + struct dept_task *dt = dept_task(); + unsigned long irqf; + unsigned long prev; + int irq; + + prev = dt->eff_enirqf; + irqf = cur_enirqf(); + dt->eff_enirqf = irqf; + + /* + * Do enirq_transition() only on an OFF -> ON transition. + */ + for_each_set_bit(irq, &irqf, DEPT_IRQS_NR) { + if (prev & (1UL << irq)) + continue; + + dt->enirq_ip[irq] = ip; + enirq_transition(irq); + } +} + +/* + * Ensure it has been called on OFF -> ON transition. + */ +void dept_enable_softirq(unsigned long ip) +{ + struct dept_task *dt = dept_task(); + unsigned long flags; + + if (READ_ONCE(dept_stop) || dt->recursive) + return; + + flags = dept_enter(); + + if (DEPT_WARN_ON(early_boot_irqs_disabled)) + goto exit; + + if (DEPT_WARN_ON(!irqs_disabled())) + goto exit; + + dt->softirqs_enabled = true; + enirq_update(ip); +exit: + dept_exit(flags); +} + +/* + * Ensure it has been called on OFF -> ON transition. + */ +void dept_enable_hardirq(unsigned long ip) +{ + struct dept_task *dt = dept_task(); + unsigned long flags; + + if (READ_ONCE(dept_stop) || dt->recursive) + return; + + flags = dept_enter(); + + if (DEPT_WARN_ON(early_boot_irqs_disabled)) + goto exit; + + if (DEPT_WARN_ON(!irqs_disabled())) + goto exit; + + dt->hardirqs_enabled = true; + enirq_update(ip); +exit: + dept_exit(flags); +} + +/* + * Ensure it has been called on ON -> OFF transition. + */ +void dept_disable_softirq(unsigned long ip) +{ + struct dept_task *dt = dept_task(); + unsigned long flags; + + if (READ_ONCE(dept_stop) || dt->recursive) + return; + + flags = dept_enter(); + + if (DEPT_WARN_ON(!irqs_disabled())) + goto exit; + + dt->softirqs_enabled = false; + enirq_update(ip); +exit: + dept_exit(flags); +} + +/* + * Ensure it has been called on ON -> OFF transition. + */ +void dept_disable_hardirq(unsigned long ip) +{ + struct dept_task *dt = dept_task(); + unsigned long flags; + + if (READ_ONCE(dept_stop) || dt->recursive) + return; + + flags = dept_enter(); + + if (DEPT_WARN_ON(!irqs_disabled())) + goto exit; + + dt->hardirqs_enabled = false; + enirq_update(ip); +exit: + dept_exit(flags); +} + +/* + * Ensure it's the outmost softirq context. + */ +void dept_softirq_enter(void) +{ + struct dept_task *dt = dept_task(); + + dt->irq_id[DEPT_SIRQ] += (1UL << DEPT_IRQS_NR); +} + +/* + * Ensure it's the outmost hardirq context. + */ +void dept_hardirq_enter(void) +{ + struct dept_task *dt = dept_task(); + + dt->irq_id[DEPT_HIRQ] += (1UL << DEPT_IRQS_NR); +} + +/* + * DEPT API + * ===================================================================== + * Main DEPT APIs. + */ + +static inline void clean_classes_cache(struct dept_key *k) +{ + int i; + + for (i = 0; i < DEPT_MAX_SUBCLASSES_CACHE; i++) + k->classes[i] = NULL; +} + +void dept_map_init(struct dept_map *m, struct dept_key *k, int sub, + const char *n) +{ + struct dept_task *dt = dept_task(); + unsigned long flags; + + if (READ_ONCE(dept_stop) || dt->recursive) + return; + + flags = dept_enter(); + + if (DEPT_WARN_ON(sub < 0 || sub >= DEPT_MAX_SUBCLASSES_USR)) { + m->nocheck = true; + goto exit; + } + + if (m->keys != k) + m->keys = k; + clean_classes_cache(&m->keys_local); + + m->sub_usr = sub; + m->name = n; + m->wgen = 0U; + m->nocheck = false; +exit: + dept_exit(flags); +} +EXPORT_SYMBOL_GPL(dept_map_init); + +void dept_map_reinit(struct dept_map *m) +{ + struct dept_task *dt = dept_task(); + unsigned long flags; + + if (READ_ONCE(dept_stop) || dt->recursive) + return; + + if (m->nocheck) + return; + + flags = dept_enter(); + + clean_classes_cache(&m->keys_local); + m->wgen = 0U; + + dept_exit(flags); +} +EXPORT_SYMBOL_GPL(dept_map_reinit); + +void dept_map_nocheck(struct dept_map *m) +{ + struct dept_task *dt = dept_task(); + unsigned long flags; + + if (READ_ONCE(dept_stop) || dt->recursive) + return; + + flags = dept_enter(); + + m->nocheck = true; + + dept_exit(flags); +} +EXPORT_SYMBOL_GPL(dept_map_nocheck); + +static LIST_HEAD(classes); + +static inline bool within(const void *addr, void *start, unsigned long size) +{ + return addr >= start && addr < start + size; +} + +void dept_free_range(void *start, unsigned int sz) +{ + struct dept_task *dt = dept_task(); + struct dept_class *c, *n; + unsigned long flags; + + if (READ_ONCE(dept_stop) || dt->recursive) + return; + + flags = dept_enter(); + + /* + * dept_free_range() should not fail. + * + * FIXME: Should be fixed if dept_free_range() causes deadlock + * with dept_lock(). + */ + while (unlikely(!dept_lock())) + cpu_relax(); + + list_for_each_entry_safe(c, n, &classes, all_node) { + if (!within((void *)c->key, start, sz) && + !within(c->name, start, sz)) + continue; + + hash_del_class(c); + disconnect_class(c); + list_del(&c->all_node); + inval_class(c); + + /* + * Actual deletion will happen on the rcu callback + * that has been added in disconnect_class(). + */ + del_class(c); + } + dept_unlock(); + dept_exit(flags); + + /* + * Wait until even lockless hash_lookup_class() for the class + * returns NULL. + */ + might_sleep(); + synchronize_rcu(); +} + +static inline int map_sub(struct dept_map *m, int e) +{ + return m->sub_usr + e * DEPT_MAX_SUBCLASSES_USR; +} + +static struct dept_class *check_new_class(struct dept_key *local, + struct dept_key *k, int sub, + const char *n) +{ + struct dept_class *c = NULL; + + if (DEPT_WARN_ON(sub >= DEPT_MAX_SUBCLASSES)) + return NULL; + + if (DEPT_WARN_ON(!k)) + return NULL; + + if (sub < DEPT_MAX_SUBCLASSES_CACHE) + c = READ_ONCE(local->classes[sub]); + + if (c) + return c; + + c = lookup_class((unsigned long)k->subkeys + sub); + if (c) + goto caching; + + if (unlikely(!dept_lock())) + return NULL; + + c = lookup_class((unsigned long)k->subkeys + sub); + if (unlikely(c)) + goto unlock; + + c = new_class(); + if (unlikely(!c)) + goto unlock; + + c->name = n; + c->sub = sub; + c->key = (unsigned long)(k->subkeys + sub); + hash_add_class(c); + list_add(&c->all_node, &classes); +unlock: + dept_unlock(); +caching: + if (sub < DEPT_MAX_SUBCLASSES_CACHE && c) + WRITE_ONCE(local->classes[sub], c); + + return c; +} + +void __dept_wait(struct dept_map *m, unsigned long w_f, unsigned long ip, + const char *w_fn, int ne) +{ + int e; + + /* + * Be as conservative as possible. In case of mulitple waits for + * a single dept_map, we are going to keep only the last wait's + * wgen for simplicity - keeping all wgens seems overengineering. + * + * Of course, it might cause missing some dependencies that + * would rarely, probabily never, happen but it helps avoid + * false positive report. + */ + for_each_set_bit(e, &w_f, DEPT_MAX_SUBCLASSES_EVT) { + struct dept_class *c; + struct dept_key *k; + + k = m->keys ?: &m->keys_local; + c = check_new_class(&m->keys_local, k, + map_sub(m, e), m->name); + if (!c) + continue; + + add_wait(c, ip, w_fn, ne); + } +} + +void dept_wait(struct dept_map *m, unsigned long w_f, unsigned long ip, + const char *w_fn, int ne) +{ + struct dept_task *dt = dept_task(); + unsigned long flags; + + if (READ_ONCE(dept_stop) || dt->recursive) + return; + + if (m->nocheck) + return; + + flags = dept_enter(); + + __dept_wait(m, w_f, ip, w_fn, ne); + + dept_exit(flags); +} +EXPORT_SYMBOL_GPL(dept_wait); + +static inline void stage_map(struct dept_task *dt, struct dept_map *m) +{ + dt->stage_m = m; +} + +static inline void unstage_map(struct dept_task *dt) +{ + dt->stage_m = NULL; +} + +static inline struct dept_map *staged_map(struct dept_task *dt) +{ + return dt->stage_m; +} + +void dept_stage_wait(struct dept_map *m, unsigned long w_f, + const char *w_fn, int ne) +{ + struct dept_task *dt = dept_task(); + unsigned long flags; + + if (READ_ONCE(dept_stop) || dt->recursive) + return; + + if (m->nocheck) + return; + + flags = dept_enter(); + + stage_map(dt, m); + + dt->stage_w_f = w_f; + dt->stage_w_fn = w_fn; + dt->stage_ne = ne; + + dept_exit(flags); +} +EXPORT_SYMBOL_GPL(dept_stage_wait); + +void dept_clean_stage(void) +{ + struct dept_task *dt = dept_task(); + unsigned long flags; + + if (READ_ONCE(dept_stop) || dt->recursive) + return; + + flags = dept_enter(); + + unstage_map(dt); + + dt->stage_w_f = 0UL; + dt->stage_w_fn = NULL; + dt->stage_ne = 0; + + dept_exit(flags); +} +EXPORT_SYMBOL_GPL(dept_clean_stage); + +/* + * Always called from __schedule(). + */ +void dept_ask_event_wait_commit(unsigned long ip) +{ + struct dept_task *dt = dept_task(); + unsigned long flags; + unsigned int wg; + struct dept_map *m; + unsigned long w_f; + const char *w_fn; + int ne; + + if (READ_ONCE(dept_stop) || dt->recursive) + return; + + flags = dept_enter(); + + m = staged_map(dt); + + /* + * Checks if current has staged a wait before __schedule(). + */ + if (!m) + goto exit; + + if (m->nocheck) + goto exit; + + w_f = dt->stage_w_f; + w_fn = dt->stage_w_fn; + ne = dt->stage_ne; + + /* + * Avoid zero wgen. + */ + wg = atomic_inc_return(&wgen) ?: atomic_inc_return(&wgen); + WRITE_ONCE(m->wgen, wg); + + __dept_wait(m, w_f, ip, w_fn, ne); +exit: + dept_exit(flags); +} + +void dept_ecxt_enter(struct dept_map *m, unsigned long e_f, unsigned long ip, + const char *c_fn, const char *e_fn, int ne) +{ + struct dept_task *dt = dept_task(); + unsigned long flags; + int e; + + if (READ_ONCE(dept_stop) || dt->recursive) + return; + + if (m->nocheck) + return; + + flags = dept_enter(); + + for_each_set_bit(e, &e_f, DEPT_MAX_SUBCLASSES_EVT) { + struct dept_class *c; + struct dept_key *k; + + k = m->keys ?: &m->keys_local; + c = check_new_class(&m->keys_local, k, + map_sub(m, e), m->name); + if (!c) + continue; + + add_ecxt((void *)m, c, ip, c_fn, e_fn, ne); + } + dept_exit(flags); +} +EXPORT_SYMBOL_GPL(dept_ecxt_enter); + +void dept_ask_event(struct dept_map *m) +{ + struct dept_task *dt = dept_task(); + unsigned long flags; + unsigned int wg; + + if (READ_ONCE(dept_stop) || dt->recursive) + return; + + if (m->nocheck) + return; + + flags = dept_enter(); + + /* + * Avoid zero wgen. + */ + wg = atomic_inc_return(&wgen) ?: atomic_inc_return(&wgen); + WRITE_ONCE(m->wgen, wg); + + dept_exit(flags); +} +EXPORT_SYMBOL_GPL(dept_ask_event); + +void dept_event(struct dept_map *m, unsigned long e_f, unsigned long ip, + const char *e_fn) +{ + struct dept_task *dt = dept_task(); + unsigned long flags; + int e; + + if (READ_ONCE(dept_stop) || dt->recursive) + return; + + if (m->nocheck) + return; + + flags = dept_enter(); + + for_each_set_bit(e, &e_f, DEPT_MAX_SUBCLASSES_EVT) { + struct dept_class *c; + struct dept_key *k; + + k = m->keys ?: &m->keys_local; + c = check_new_class(&m->keys_local, k, + map_sub(m, e), m->name); + if (!c) + continue; + + add_ecxt((void *)m, c, 0UL, NULL, e_fn, 0); + do_event((void *)m, c, READ_ONCE(m->wgen), ip); + pop_ecxt((void *)m); + } + dept_exit(flags); +} +EXPORT_SYMBOL_GPL(dept_event); + +void dept_ecxt_exit(struct dept_map *m, unsigned long ip) +{ + struct dept_task *dt = dept_task(); + unsigned long flags; + + if (READ_ONCE(dept_stop) || dt->recursive) + return; + + if (m->nocheck) + return; + + flags = dept_enter(); + pop_ecxt((void *)m); + dept_exit(flags); +} +EXPORT_SYMBOL_GPL(dept_ecxt_exit); + +void dept_task_exit(struct task_struct *t) +{ + struct dept_task *dt = &t->dept_task; + int i; + + raw_local_irq_disable(); + + if (dt->stack) + put_stack(dt->stack); + + for (i = 0; i < dt->ecxt_held_pos; i++) + put_ecxt(dt->ecxt_held[i].ecxt); + + for (i = 0; i < DEPT_MAX_WAIT_HIST; i++) + if (dt->wait_hist[i].wait) + put_wait(dt->wait_hist[i].wait); + + dept_off(); + + raw_local_irq_enable(); +} + +void dept_task_init(struct task_struct *t) +{ + memset(&t->dept_task, 0x0, sizeof(struct dept_task)); +} + +void dept_key_init(struct dept_key *k) +{ + struct dept_task *dt = dept_task(); + unsigned long flags; + int sub; + + if (READ_ONCE(dept_stop) || dt->recursive) + return; + + flags = dept_enter(); + + /* + * dept_key_init() should not fail. + * + * FIXME: Should be fixed if dept_key_init() causes deadlock + * with dept_lock(). + */ + while (unlikely(!dept_lock())) + cpu_relax(); + + for (sub = 0; sub < DEPT_MAX_SUBCLASSES; sub++) { + struct dept_class *c; + + c = lookup_class((unsigned long)k->subkeys + sub); + if (!c) + continue; + + DEPT_STOP("The class(%s/%d) has not been removed.\n", + c->name, sub); + break; + } + + dept_unlock(); + dept_exit(flags); +} +EXPORT_SYMBOL_GPL(dept_key_init); + +void dept_key_destroy(struct dept_key *k) +{ + struct dept_task *dt = dept_task(); + unsigned long flags; + int sub; + + if (READ_ONCE(dept_stop) || dt->recursive) + return; + + flags = dept_enter(); + + /* + * dept_key_destroy() should not fail. + * + * FIXME: Should be fixed if dept_key_destroy() causes deadlock + * with dept_lock(). + */ + while (unlikely(!dept_lock())) + cpu_relax(); + + for (sub = 0; sub < DEPT_MAX_SUBCLASSES; sub++) { + struct dept_class *c; + + c = lookup_class((unsigned long)k->subkeys + sub); + if (!c) + continue; + + hash_del_class(c); + disconnect_class(c); + list_del(&c->all_node); + inval_class(c); + + /* + * Actual deletion will happen on the rcu callback + * that has been added in disconnect_class(). + */ + del_class(c); + } + + dept_unlock(); + dept_exit(flags); + + /* + * Wait until even lockless hash_lookup_class() for the class + * returns NULL. + */ + might_sleep(); + synchronize_rcu(); +} +EXPORT_SYMBOL_GPL(dept_key_destroy); + +static void move_llist(struct llist_head *to, struct llist_head *from) +{ + struct llist_node *first = llist_del_all(from); + struct llist_node *last; + + if (!first) + return; + + for (last = first; last->next; last = last->next); + llist_add_batch(first, last, to); +} + +static void migrate_per_cpu_pool(void) +{ + const int boot_cpu = 0; + int i; + + /* + * The boot CPU has been using the temperal local pool so far. + * From now on that per_cpu areas have been ready, use the + * per_cpu local pool instead. + */ + DEPT_WARN_ON(smp_processor_id() != boot_cpu); + for (i = 0; i < OBJECT_NR; i++) { + struct llist_head *from; + struct llist_head *to; + + from = &pool[i].boot_pool; + to = per_cpu_ptr(pool[i].lpool, boot_cpu); + move_llist(to, from); + } +} + +#define B2KB(B) ((B) / 1024) + +/* + * Should be called after setup_per_cpu_areas() and before no non-boot + * CPUs have been on. + */ +void __init dept_init(void) +{ + size_t mem_total = 0; + + local_irq_disable(); + dept_per_cpu_ready = 1; + migrate_per_cpu_pool(); + local_irq_enable(); + +#define OBJECT(id, nr) mem_total += sizeof(struct dept_##id) * nr; + #include "dept_object.h" +#undef OBJECT +#define HASH(id, bits) mem_total += sizeof(struct hlist_head) * (1UL << bits); + #include "dept_hash.h" +#undef HASH + + pr_info("DEPendency Tracker: Copyright (c) 2020 LG Electronics, Inc., Byungchul Park\n"); + pr_info("... DEPT_MAX_STACK_ENTRY: %d\n", DEPT_MAX_STACK_ENTRY); + pr_info("... DEPT_MAX_WAIT_HIST : %d\n", DEPT_MAX_WAIT_HIST); + pr_info("... DEPT_MAX_ECXT_HELD : %d\n", DEPT_MAX_ECXT_HELD); + pr_info("... DEPT_MAX_SUBCLASSES : %d\n", DEPT_MAX_SUBCLASSES); +#define OBJECT(id, nr) \ + pr_info("... memory used by %s: %zu KB\n", \ + #id, B2KB(sizeof(struct dept_##id) * nr)); + #include "dept_object.h" +#undef OBJECT +#define HASH(id, bits) \ + pr_info("... hash list head used by %s: %zu KB\n", \ + #id, B2KB(sizeof(struct hlist_head) * (1UL << bits))); + #include "dept_hash.h" +#undef HASH + pr_info("... total memory used by objects and hashs: %zu KB\n", B2KB(mem_total)); + pr_info("... per task memory footprint: %zu bytes\n", sizeof(struct dept_task)); +} diff --git a/kernel/dependency/dept_hash.h b/kernel/dependency/dept_hash.h new file mode 100644 index 0000000..fd85aab --- /dev/null +++ b/kernel/dependency/dept_hash.h @@ -0,0 +1,10 @@ +/* SPDX-License-Identifier: GPL-2.0 */ +/* + * HASH(id, bits) + * + * id : Id for the object of struct dept_##id. + * bits: 1UL << bits is the hash table size. + */ + +HASH(dep, 12) +HASH(class, 12) diff --git a/kernel/dependency/dept_object.h b/kernel/dependency/dept_object.h new file mode 100644 index 0000000..ad5ff57 --- /dev/null +++ b/kernel/dependency/dept_object.h @@ -0,0 +1,13 @@ +/* SPDX-License-Identifier: GPL-2.0 */ +/* + * OBJECT(id, nr) + * + * id: Id for the object of struct dept_##id. + * nr: # of the object that should be kept in the pool. + */ + +OBJECT(dep, 1024 * 8) +OBJECT(class, 1024 * 4) +OBJECT(stack, 1024 * 32) +OBJECT(ecxt, 1024 * 4) +OBJECT(wait, 1024 * 32) diff --git a/kernel/exit.c b/kernel/exit.c index b00a25b..187ee24 100644 --- a/kernel/exit.c +++ b/kernel/exit.c @@ -854,6 +854,7 @@ void __noreturn do_exit(long code) exit_tasks_rcu_finish();

lockdep_free_task(tsk); + dept_task_exit(tsk); do_task_dead(); }

diff --git a/kernel/fork.c b/kernel/fork.c index d75a528f..8de918b 100644 --- a/kernel/fork.c +++ b/kernel/fork.c @@ -97,6 +97,7 @@ #include <linux/scs.h> #include <linux/io_uring.h> #include <linux/bpf.h> +#include <linux/dept.h>

#include <asm/pgalloc.h> #include <linux/uaccess.h> @@ -2117,6 +2118,7 @@ static __latent_entropy struct task_struct *copy_process( #ifdef CONFIG_LOCKDEP lockdep_init_task(p); #endif + dept_task_init(p);

#ifdef CONFIG_DEBUG_MUTEXES p->blocked_on = NULL; /* not blocked yet */ diff --git a/kernel/module.c b/kernel/module.c index 24dab04..bd9376d 100644 --- a/kernel/module.c +++ b/kernel/module.c @@ -2205,6 +2205,7 @@ static void free_module(struct module *mod)

/* Free lock-classes; relies on the preceding sync_rcu(). */ lockdep_free_key_range(mod->core_layout.base, mod->core_layout.size); + dept_free_range(mod->core_layout.base, mod->core_layout.size);

/* Finally, free the core (containing the module structure) */ module_memfree(mod->core_layout.base); @@ -4174,6 +4175,7 @@ static int load_module(struct load_info *info, const char __user *uargs, free_module: /* Free lock-classes; relies on the preceding sync_rcu() */ lockdep_free_key_range(mod->core_layout.base, mod->core_layout.size); + dept_free_range(mod->core_layout.base, mod->core_layout.size);

module_deallocate(mod, info); free_copy: diff --git a/kernel/sched/core.c b/kernel/sched/core.c index 2e4ae00..6a422aa 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -6192,6 +6192,9 @@ static void __sched notrace __schedule(unsigned int sched_mode) local_irq_disable(); rcu_note_context_switch(!!sched_mode);

+ if (sched_mode == SM_NONE) + dept_ask_event_wait_commit(_RET_IP_); + /* * Make sure that signal_pending_state()->signal_pending() below * can't be reordered with __set_current_state(TASK_INTERRUPTIBLE) diff --git a/kernel/softirq.c b/kernel/softirq.c index 41f4709..a28c950 100644 --- a/kernel/softirq.c +++ b/kernel/softirq.c @@ -320,7 +320,7 @@ void __local_bh_disable_ip(unsigned long ip, unsigned int cnt) * Were softirqs turned off above: */ if (softirq_count() == (cnt & SOFTIRQ_MASK)) - lockdep_softirqs_off(ip); + trace_softirqs_off_caller(ip); raw_local_irq_restore(flags);

if (preempt_count() == cnt) { @@ -341,7 +341,7 @@ static void __local_bh_enable(unsigned int cnt) trace_preempt_on(CALLER_ADDR0, get_lock_parent_ip());

if (softirq_count() == (cnt & SOFTIRQ_MASK)) - lockdep_softirqs_on(_RET_IP_); + trace_softirqs_on_caller(_RET_IP_);

__preempt_count_sub(cnt); } @@ -368,7 +368,7 @@ void __local_bh_enable_ip(unsigned long ip, unsigned int cnt) * Are softirqs going to be turned on now: */ if (softirq_count() == SOFTIRQ_DISABLE_OFFSET) - lockdep_softirqs_on(ip); + trace_softirqs_on_caller(ip); /* * Keep preemption disabled until we are done with * softirq processing: diff --git a/kernel/trace/trace_preemptirq.c b/kernel/trace/trace_preemptirq.c index f493804..19cafdfb 100644 --- a/kernel/trace/trace_preemptirq.c +++ b/kernel/trace/trace_preemptirq.c @@ -19,6 +19,18 @@ /* Per-cpu variable to prevent redundant calls when IRQs already off */ static DEFINE_PER_CPU(int, tracing_irq_cpu);

+void trace_softirqs_on_caller(unsigned long ip) +{ + lockdep_softirqs_on(ip); + dept_enable_softirq(ip); +} + +void trace_softirqs_off_caller(unsigned long ip) +{ + lockdep_softirqs_off(ip); + dept_disable_softirq(ip); +} + /* * Like trace_hardirqs_on() but without the lockdep invocation. This is * used in the low level entry code where the ordering vs. RCU is important @@ -33,6 +45,7 @@ void trace_hardirqs_on_prepare(void) tracer_hardirqs_on(CALLER_ADDR0, CALLER_ADDR1); this_cpu_write(tracing_irq_cpu, 0); } + dept_enable_hardirq(CALLER_ADDR0); } EXPORT_SYMBOL(trace_hardirqs_on_prepare); NOKPROBE_SYMBOL(trace_hardirqs_on_prepare); @@ -45,6 +58,7 @@ void trace_hardirqs_on(void) tracer_hardirqs_on(CALLER_ADDR0, CALLER_ADDR1); this_cpu_write(tracing_irq_cpu, 0); } + dept_enable_hardirq(CALLER_ADDR0);

lockdep_hardirqs_on_prepare(CALLER_ADDR0); lockdep_hardirqs_on(CALLER_ADDR0); @@ -66,7 +80,7 @@ void trace_hardirqs_off_finish(void) if (!in_nmi()) trace_irq_disable(CALLER_ADDR0, CALLER_ADDR1); } - + dept_disable_hardirq(CALLER_ADDR0); } EXPORT_SYMBOL(trace_hardirqs_off_finish); NOKPROBE_SYMBOL(trace_hardirqs_off_finish); @@ -81,6 +95,7 @@ void trace_hardirqs_off(void) if (!in_nmi()) trace_irq_disable_rcuidle(CALLER_ADDR0, CALLER_ADDR1); } + dept_disable_hardirq(CALLER_ADDR0); } EXPORT_SYMBOL(trace_hardirqs_off); NOKPROBE_SYMBOL(trace_hardirqs_off); @@ -93,6 +108,7 @@ __visible void trace_hardirqs_on_caller(unsigned long caller_addr) tracer_hardirqs_on(CALLER_ADDR0, caller_addr); this_cpu_write(tracing_irq_cpu, 0); } + dept_enable_hardirq(CALLER_ADDR0);

lockdep_hardirqs_on_prepare(CALLER_ADDR0); lockdep_hardirqs_on(CALLER_ADDR0); @@ -110,6 +126,7 @@ __visible void trace_hardirqs_off_caller(unsigned long caller_addr) if (!in_nmi()) trace_irq_disable_rcuidle(CALLER_ADDR0, caller_addr); } + dept_disable_hardirq(CALLER_ADDR0); } EXPORT_SYMBOL(trace_hardirqs_off_caller); NOKPROBE_SYMBOL(trace_hardirqs_off_caller); diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug index 14b89aa..309b275 100644 --- a/lib/Kconfig.debug +++ b/lib/Kconfig.debug @@ -1233,6 +1233,26 @@ config DEBUG_PREEMPT

menu "Lock Debugging (spinlocks, mutexes, etc...)"

+config DEPT + bool "Dependency tracking" + depends on DEBUG_KERNEL && LOCK_DEBUGGING_SUPPORT + select DEBUG_SPINLOCK + select DEBUG_MUTEXES + select DEBUG_RT_MUTEXES if RT_MUTEXES + select DEBUG_RWSEMS + select DEBUG_WW_MUTEX_SLOWPATH + select DEBUG_LOCK_ALLOC + select TRACE_IRQFLAGS + select STACKTRACE + select FRAME_POINTER if !MIPS && !PPC && !ARM && !S390 && !MICROBLAZE && !ARC && !X86 + select KALLSYMS + select KALLSYMS_ALL + default n + help + Check dependencies between wait and event and report it if + deadlock possibility has been detected. Multiple reports are + allowed if there are more than a single problem. + config LOCK_DEBUGGING_SUPPORT bool depends on TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT

Dept would skip check for dmaps marked by dept_map_nocheck() permanently. However, sometimes it needs to skip check for some dmaps temporarily and back to normal, for instance, lock acquisition with a nest lock.

Lock usage check with regard to nest lock could be performed by Lockdep, however, dependency check is not necessary for that case. So prepared for it by adding two new APIs, dept_skip() and dept_unskip_if_skipped().

Signed-off-by: Byungchul Park byungchul.park@lge.com --- include/linux/dept.h | 9 +++++++++ include/linux/dept_sdt.h | 2 +- include/linux/lockdep.h | 4 +++- kernel/dependency/dept.c | 49 ++++++++++++++++++++++++++++++++++++++++++++++++ 4 files changed, 62 insertions(+), 2 deletions(-)

diff --git a/include/linux/dept.h b/include/linux/dept.h index c3fb3cf..c0bbb8e 100644 --- a/include/linux/dept.h +++ b/include/linux/dept.h @@ -352,6 +352,11 @@ struct dept_map { unsigned int wgen;

/* + * for skipping dependency check temporarily + */ + atomic_t skip_cnt; + + /* * whether this map should be going to be checked or not */ bool nocheck; @@ -444,6 +449,8 @@ struct dept_task { extern void dept_ask_event(struct dept_map *m); extern void dept_event(struct dept_map *m, unsigned long e_f, unsigned long ip, const char *e_fn); extern void dept_ecxt_exit(struct dept_map *m, unsigned long ip); +extern void dept_skip(struct dept_map *m); +extern bool dept_unskip_if_skipped(struct dept_map *m);

/* * for users who want to manage external keys @@ -475,6 +482,8 @@ struct dept_task { #define dept_ask_event(m) do { } while (0) #define dept_event(m, e_f, ip, e_fn) do { (void)(e_fn); } while (0) #define dept_ecxt_exit(m, ip) do { } while (0) +#define dept_skip(m) do { } while (0) +#define dept_unskip_if_skipped(m) (false) #define dept_key_init(k) do { (void)(k); } while (0) #define dept_key_destroy(k) do { (void)(k); } while (0) #endif diff --git a/include/linux/dept_sdt.h b/include/linux/dept_sdt.h index 375c4c3..e9d558d 100644 --- a/include/linux/dept_sdt.h +++ b/include/linux/dept_sdt.h @@ -13,7 +13,7 @@ #include <linux/dept.h>

#ifdef CONFIG_DEPT -#define DEPT_SDT_MAP_INIT(dname) { .name = #dname } +#define DEPT_SDT_MAP_INIT(dname) { .name = #dname, .skip_cnt = ATOMIC_INIT(0) }

/* * SDT(Single-event Dependency Tracker) APIs diff --git a/include/linux/lockdep.h b/include/linux/lockdep.h index c56f6b6..c1a56fe 100644 --- a/include/linux/lockdep.h +++ b/include/linux/lockdep.h @@ -488,7 +488,9 @@ enum xhlock_context_t { */ #define STATIC_DEPT_MAP_INIT(_name, _key) .dmap = { \ .name = (_name), \ - .keys = NULL }, + .keys = NULL, \ + .skip_cnt = ATOMIC_INIT(0), \ + }, #else #define STATIC_DEPT_MAP_INIT(_name, _key) #endif diff --git a/kernel/dependency/dept.c b/kernel/dependency/dept.c index ec3f131..3f22c5b 100644 --- a/kernel/dependency/dept.c +++ b/kernel/dependency/dept.c @@ -1943,6 +1943,7 @@ void dept_map_init(struct dept_map *m, struct dept_key *k, int sub, m->name = n; m->wgen = 0U; m->nocheck = false; + atomic_set(&m->skip_cnt, 0); exit: dept_exit(flags); } @@ -1963,6 +1964,7 @@ void dept_map_reinit(struct dept_map *m)

clean_classes_cache(&m->keys_local); m->wgen = 0U; + atomic_set(&m->skip_cnt, 0);

dept_exit(flags); } @@ -2346,6 +2348,53 @@ void dept_ecxt_exit(struct dept_map *m, unsigned long ip) } EXPORT_SYMBOL_GPL(dept_ecxt_exit);

+void dept_skip(struct dept_map *m) +{ + struct dept_task *dt = dept_task(); + unsigned long flags; + + if (READ_ONCE(dept_stop) || dt->recursive) + return; + + if (m->nocheck) + return; + + flags = dept_enter(); + + atomic_inc(&m->skip_cnt); + + dept_exit(flags); +} +EXPORT_SYMBOL_GPL(dept_skip); + +/* + * Return true if successfully unskip, otherwise false. + */ +bool dept_unskip_if_skipped(struct dept_map *m) +{ + struct dept_task *dt = dept_task(); + unsigned long flags; + bool ret = false; + + if (READ_ONCE(dept_stop) || dt->recursive) + return false; + + if (m->nocheck) + return false; + + flags = dept_enter(); + + if (!atomic_read(&m->skip_cnt)) + goto exit; + + atomic_dec(&m->skip_cnt); + ret = true; +exit: + dept_exit(flags); + return ret; +} +EXPORT_SYMBOL_GPL(dept_unskip_if_skipped); + void dept_task_exit(struct task_struct *t) { struct dept_task *dt = &t->dept_task;

Makes Dept able to track dependencies by mutex families.

Signed-off-by: Byungchul Park byungchul.park@lge.com --- include/linux/lockdep.h | 18 +++++++++++++++--- include/linux/mutex.h | 33 +++++++++++++++++++++++++++++++++ include/linux/rtmutex.h | 7 +++++++ 3 files changed, 55 insertions(+), 3 deletions(-)

diff --git a/include/linux/lockdep.h b/include/linux/lockdep.h index 529ea18..6653a4f 100644 --- a/include/linux/lockdep.h +++ b/include/linux/lockdep.h @@ -615,9 +615,21 @@ static inline void print_irqtrace_events(struct task_struct *curr) #define seqcount_acquire_read(l, s, t, i) lock_acquire_shared_recursive(l, s, t, NULL, i) #define seqcount_release(l, i) lock_release(l, i)

-#define mutex_acquire(l, s, t, i) lock_acquire_exclusive(l, s, t, NULL, i) -#define mutex_acquire_nest(l, s, t, n, i) lock_acquire_exclusive(l, s, t, n, i) -#define mutex_release(l, i) lock_release(l, i) +#define mutex_acquire(l, s, t, i) \ +do { \ + lock_acquire_exclusive(l, s, t, NULL, i); \ + dept_mutex_lock(&(l)->dmap, s, t, NULL, "mutex_unlock", i); \ +} while (0) +#define mutex_acquire_nest(l, s, t, n, i) \ +do { \ + lock_acquire_exclusive(l, s, t, n, i); \ + dept_mutex_lock(&(l)->dmap, s, t, (n) ? &(n)->dmap : NULL, "mutex_unlock", i);\ +} while (0) +#define mutex_release(l, i) \ +do { \ + lock_release(l, i); \ + dept_mutex_unlock(&(l)->dmap, i); \ +} while (0)

#define rwsem_acquire(l, s, t, i) lock_acquire_exclusive(l, s, t, NULL, i) #define rwsem_acquire_nest(l, s, t, n, i) lock_acquire_exclusive(l, s, t, n, i) diff --git a/include/linux/mutex.h b/include/linux/mutex.h index 8f226d4..204f976 100644 --- a/include/linux/mutex.h +++ b/include/linux/mutex.h @@ -20,11 +20,18 @@ #include <linux/osq_lock.h> #include <linux/debug_locks.h>

+#ifdef CONFIG_DEPT +# define DMAP_MUTEX_INIT(lockname) .dmap = { .name = #lockname, .skip_cnt = ATOMIC_INIT(0) }, +#else +# define DMAP_MUTEX_INIT(lockname) +#endif + #ifdef CONFIG_DEBUG_LOCK_ALLOC # define __DEP_MAP_MUTEX_INITIALIZER(lockname) \ , .dep_map = { \ .name = #lockname, \ .wait_type_inner = LD_WAIT_SLEEP, \ + DMAP_MUTEX_INIT(lockname) \ } #else # define __DEP_MAP_MUTEX_INITIALIZER(lockname) @@ -75,6 +82,32 @@ struct mutex { #endif };

+#ifdef CONFIG_DEPT +#define dept_mutex_lock(m, ne, t, n, e_fn, ip) \ +do { \ + if (t) { \ + dept_ecxt_enter(m, 1UL, ip, __func__, e_fn, ne); \ + dept_ask_event(m); \ + } else if (n) { \ + dept_skip(m); \ + } else { \ + dept_wait(m, 1UL, ip, __func__, ne); \ + dept_ecxt_enter(m, 1UL, ip, __func__, e_fn, ne); \ + dept_ask_event(m); \ + } \ +} while (0) +#define dept_mutex_unlock(m, ip) \ +do { \ + if (!dept_unskip_if_skipped(m)) { \ + dept_event(m, 1UL, ip, __func__); \ + dept_ecxt_exit(m, ip); \ + } \ +} while (0) +#else +#define dept_mutex_lock(m, ne, t, n, e_fn, ip) do { } while (0) +#define dept_mutex_unlock(m, ip) do { } while (0) +#endif + #ifdef CONFIG_DEBUG_MUTEXES

#define __DEBUG_MUTEX_INITIALIZER(lockname) \ diff --git a/include/linux/rtmutex.h b/include/linux/rtmutex.h index 7d04988..712d6e6 100644 --- a/include/linux/rtmutex.h +++ b/include/linux/rtmutex.h @@ -76,11 +76,18 @@ static inline void rt_mutex_debug_task_free(struct task_struct *tsk) { } __rt_mutex_init(mutex, __func__, &__key); \ } while (0)

+#ifdef CONFIG_DEPT +#define DMAP_RT_MUTEX_INIT(mutexname) .dmap = { .name = #mutexname, .skip_cnt = ATOMIC_INIT(0) }, +#else +#define DMAP_RT_MUTEX_INIT(mutexname) +#endif + #ifdef CONFIG_DEBUG_LOCK_ALLOC #define __DEP_MAP_RT_MUTEX_INITIALIZER(mutexname) \ .dep_map = { \ .name = #mutexname, \ .wait_type_inner = LD_WAIT_SLEEP, \ + DMAP_RT_MUTEX_INIT(mutexname) \ } #else #define __DEP_MAP_RT_MUTEX_INITIALIZER(mutexname)

Makes Dept able to track dependencies by wait_for_completion()/complete().

Signed-off-by: Byungchul Park byungchul.park@lge.com --- include/linux/completion.h | 42 ++++++++++++++++++++++++++++++++++++++++-- kernel/sched/completion.c | 12 ++++++++++-- 2 files changed, 50 insertions(+), 4 deletions(-)

diff --git a/include/linux/completion.h b/include/linux/completion.h index 51d9ab0..a1ad5a8 100644 --- a/include/linux/completion.h +++ b/include/linux/completion.h @@ -26,14 +26,48 @@ struct completion { unsigned int done; struct swait_queue_head wait; + struct dept_map dmap; };

+#ifdef CONFIG_DEPT +#define dept_wfc_init(m, k, s, n) dept_map_init(m, k, s, n) +#define dept_wfc_reinit(m) dept_map_reinit(m) +#define dept_wfc_wait(m, ip) \ +do { \ + dept_ask_event(m); \ + dept_wait(m, 1UL, ip, __func__, 0); \ +} while (0) +#define dept_wfc_complete(m, ip) dept_event(m, 1UL, ip, __func__) +#define dept_wfc_enter(m, ip) dept_ecxt_enter(m, 1UL, ip, "completion_context_enter", "complete", 0) +#define dept_wfc_exit(m, ip) dept_ecxt_exit(m, ip) +#else +#define dept_wfc_init(m, k, s, n) do { (void)(n); (void)(k); } while (0) +#define dept_wfc_reinit(m) do { } while (0) +#define dept_wfc_wait(m, ip) do { } while (0) +#define dept_wfc_complete(m, ip) do { } while (0) +#define dept_wfc_enter(m, ip) do { } while (0) +#define dept_wfc_exit(m, ip) do { } while (0) +#endif + +#ifdef CONFIG_DEPT +#define WFC_DEPT_MAP_INIT(work) .dmap = { .name = #work, .skip_cnt = ATOMIC_INIT(0) } +#else +#define WFC_DEPT_MAP_INIT(work) +#endif + +#define init_completion(x) \ + do { \ + static struct dept_key __dkey; \ + __init_completion(x, &__dkey, #x); \ + } while (0) + #define init_completion_map(x, m) init_completion(x) static inline void complete_acquire(struct completion *x) {} static inline void complete_release(struct completion *x) {}

#define COMPLETION_INITIALIZER(work) \ - { 0, __SWAIT_QUEUE_HEAD_INITIALIZER((work).wait) } + { 0, __SWAIT_QUEUE_HEAD_INITIALIZER((work).wait), \ + WFC_DEPT_MAP_INIT(work) }

#define COMPLETION_INITIALIZER_ONSTACK_MAP(work, map) \ (*({ init_completion_map(&(work), &(map)); &(work); })) @@ -81,9 +115,12 @@ static inline void complete_release(struct completion *x) {} * This inline function will initialize a dynamically created completion * structure. */ -static inline void init_completion(struct completion *x) +static inline void __init_completion(struct completion *x, + struct dept_key *dkey, + const char *name) { x->done = 0; + dept_wfc_init(&x->dmap, dkey, 0, name); init_swait_queue_head(&x->wait); }

@@ -97,6 +134,7 @@ static inline void init_completion(struct completion *x) static inline void reinit_completion(struct completion *x) { x->done = 0; + dept_wfc_reinit(&x->dmap); }

extern void wait_for_completion(struct completion *); diff --git a/kernel/sched/completion.c b/kernel/sched/completion.c index a778554..6e31cc0 100644 --- a/kernel/sched/completion.c +++ b/kernel/sched/completion.c @@ -29,6 +29,7 @@ void complete(struct completion *x) { unsigned long flags;

+ dept_wfc_complete(&x->dmap, _RET_IP_); raw_spin_lock_irqsave(&x->wait.lock, flags);

if (x->done != UINT_MAX) @@ -58,6 +59,7 @@ void complete_all(struct completion *x) { unsigned long flags;

+ dept_wfc_complete(&x->dmap, _RET_IP_); lockdep_assert_RT_in_threaded_ctx();

raw_spin_lock_irqsave(&x->wait.lock, flags); @@ -112,17 +114,23 @@ void complete_all(struct completion *x) }

static long __sched -wait_for_common(struct completion *x, long timeout, int state) +_wait_for_common(struct completion *x, long timeout, int state) { return __wait_for_common(x, schedule_timeout, timeout, state); }

static long __sched -wait_for_common_io(struct completion *x, long timeout, int state) +_wait_for_common_io(struct completion *x, long timeout, int state) { return __wait_for_common(x, io_schedule_timeout, timeout, state); }

+#define wait_for_common(x, t, s) \ +({ dept_wfc_wait(&(x)->dmap, _RET_IP_); _wait_for_common(x, t, s); }) + +#define wait_for_common_io(x, t, s) \ +({ dept_wfc_wait(&(x)->dmap, _RET_IP_); _wait_for_common_io(x, t, s); }) + /** * wait_for_completion: - waits for completion of a task * @x: holds the state of this particular completion

Makes Dept able to track dependencies by rwsem.

Signed-off-by: Byungchul Park byungchul.park@lge.com --- include/linux/lockdep.h | 24 ++++++++++++++++++++---- include/linux/percpu-rwsem.h | 10 +++++++++- include/linux/rwsem.h | 33 +++++++++++++++++++++++++++++++++ 3 files changed, 62 insertions(+), 5 deletions(-)

diff --git a/include/linux/lockdep.h b/include/linux/lockdep.h index b93a707..37af50c 100644 --- a/include/linux/lockdep.h +++ b/include/linux/lockdep.h @@ -646,10 +646,26 @@ static inline void print_irqtrace_events(struct task_struct *curr) dept_mutex_unlock(&(l)->dmap, i); \ } while (0)

-#define rwsem_acquire(l, s, t, i) lock_acquire_exclusive(l, s, t, NULL, i) -#define rwsem_acquire_nest(l, s, t, n, i) lock_acquire_exclusive(l, s, t, n, i) -#define rwsem_acquire_read(l, s, t, i) lock_acquire_shared(l, s, t, NULL, i) -#define rwsem_release(l, i) lock_release(l, i) +#define rwsem_acquire(l, s, t, i) \ +do { \ + lock_acquire_exclusive(l, s, t, NULL, i); \ + dept_rwsem_lock(&(l)->dmap, s, t, NULL, "up_write", i); \ +} while (0) +#define rwsem_acquire_nest(l, s, t, n, i) \ +do { \ + lock_acquire_exclusive(l, s, t, n, i); \ + dept_rwsem_lock(&(l)->dmap, s, t, (n) ? &(n)->dmap : NULL, "up_write", i);\ +} while (0) +#define rwsem_acquire_read(l, s, t, i) \ +do { \ + lock_acquire_shared(l, s, t, NULL, i); \ + dept_rwsem_lock(&(l)->dmap, s, t, NULL, "up_read", i); \ +} while (0) +#define rwsem_release(l, i) \ +do { \ + lock_release(l, i); \ + dept_rwsem_unlock(&(l)->dmap, i); \ +} while (0)

#define lock_map_acquire(l) lock_acquire_exclusive(l, 0, 0, NULL, _THIS_IP_) #define lock_map_acquire_read(l) lock_acquire_shared_recursive(l, 0, 0, NULL, _THIS_IP_) diff --git a/include/linux/percpu-rwsem.h b/include/linux/percpu-rwsem.h index 5fda40f..ac2b1a5 100644 --- a/include/linux/percpu-rwsem.h +++ b/include/linux/percpu-rwsem.h @@ -20,8 +20,16 @@ struct percpu_rw_semaphore { #endif };

+#ifdef CONFIG_DEPT +#define __PERCPU_RWSEM_DMAP_INIT(lockname) .dmap = { .name = #lockname, .skip_cnt = ATOMIC_INIT(0) } +#else +#define __PERCPU_RWSEM_DMAP_INIT(lockname) +#endif + #ifdef CONFIG_DEBUG_LOCK_ALLOC -#define __PERCPU_RWSEM_DEP_MAP_INIT(lockname) .dep_map = { .name = #lockname }, +#define __PERCPU_RWSEM_DEP_MAP_INIT(lockname) .dep_map = { \ + .name = #lockname, \ + __PERCPU_RWSEM_DMAP_INIT(lockname) }, #else #define __PERCPU_RWSEM_DEP_MAP_INIT(lockname) #endif diff --git a/include/linux/rwsem.h b/include/linux/rwsem.h index f934876..dc7977a 100644 --- a/include/linux/rwsem.h +++ b/include/linux/rwsem.h @@ -16,11 +16,18 @@ #include <linux/atomic.h> #include <linux/err.h>

+#ifdef CONFIG_DEPT +# define RWSEM_DMAP_INIT(lockname) .dmap = { .name = #lockname, .skip_cnt = ATOMIC_INIT(0) }, +#else +# define RWSEM_DMAP_INIT(lockname) +#endif + #ifdef CONFIG_DEBUG_LOCK_ALLOC # define __RWSEM_DEP_MAP_INIT(lockname) \ .dep_map = { \ .name = #lockname, \ .wait_type_inner = LD_WAIT_SLEEP, \ + RWSEM_DMAP_INIT(lockname) \ }, #else # define __RWSEM_DEP_MAP_INIT(lockname) @@ -32,6 +39,32 @@ #include <linux/osq_lock.h> #endif

+#ifdef CONFIG_DEPT +#define dept_rwsem_lock(m, ne, t, n, e_fn, ip) \ +do { \ + if (t) { \ + dept_ecxt_enter(m, 1UL, ip, __func__, e_fn, ne); \ + dept_ask_event(m); \ + } else if (n) { \ + dept_skip(m); \ + } else { \ + dept_wait(m, 1UL, ip, __func__, ne); \ + dept_ecxt_enter(m, 1UL, ip, __func__, e_fn, ne); \ + dept_ask_event(m); \ + } \ +} while (0) +#define dept_rwsem_unlock(m, ip) \ +do { \ + if (!dept_unskip_if_skipped(m)) { \ + dept_event(m, 1UL, ip, __func__); \ + dept_ecxt_exit(m, ip); \ + } \ +} while (0) +#else +#define dept_rwsem_lock(m, ne, t, n, e_fn, ip) do { } while (0) +#define dept_rwsem_unlock(m, ip) do { } while (0) +#endif + /* * For an uncontended rwsem, count and owner are the only fields a task * needs to touch when acquiring the rwsem. So they are put next to each

There is a case where all maps used for a type of wait/event is so large in size. For instance, struct page can be a type for (un)lock_page(). The additional memory size for the maps would be 'the # of pages * sizeof(struct dept_map)' if each struct page keeps its map all the way, which might be too big to accept in some system.

It'd better to have split map, one is for each instance and the other is for the type which is commonly used, and new APIs using them. So introduced split map and new APIs for them.

Signed-off-by: Byungchul Park byungchul.park@lge.com --- include/linux/dept.h | 80 ++++++++++++++++++++++--------- kernel/dependency/dept.c | 122 +++++++++++++++++++++++++++++++++++++++++++++++ 2 files changed, 180 insertions(+), 22 deletions(-)

diff --git a/include/linux/dept.h b/include/linux/dept.h index c0bbb8e..e2d4aea 100644 --- a/include/linux/dept.h +++ b/include/linux/dept.h @@ -362,6 +362,30 @@ struct dept_map { bool nocheck; };

+struct dept_map_each { + /* + * wait timestamp associated to this map + */ + unsigned int wgen; +}; + +struct dept_map_common { + const char *name; + struct dept_key *keys; + int sub_usr; + + /* + * It's local copy for fast acces to the associated classes. And + * Also used for dept_key instance for statically defined map. + */ + struct dept_key keys_local; + + /* + * whether this map should be going to be checked or not + */ + bool nocheck; +}; + struct dept_task { /* * all event contexts that have entered and before exiting @@ -451,6 +475,11 @@ struct dept_task { extern void dept_ecxt_exit(struct dept_map *m, unsigned long ip); extern void dept_skip(struct dept_map *m); extern bool dept_unskip_if_skipped(struct dept_map *m); +extern void dept_split_map_each_init(struct dept_map_each *me); +extern void dept_split_map_common_init(struct dept_map_common *mc, struct dept_key *k, const char *n); +extern void dept_wait_split_map(struct dept_map_each *me, struct dept_map_common *mc, unsigned long ip, const char *w_fn, int ne); +extern void dept_event_split_map(struct dept_map_each *me, struct dept_map_common *mc, unsigned long ip, const char *e_fn); +extern void dept_ask_event_split_map(struct dept_map_each *me, struct dept_map_common *mc);

/* * for users who want to manage external keys @@ -460,31 +489,38 @@ struct dept_task { #else /* !CONFIG_DEPT */ struct dept_key { }; struct dept_map { }; +struct dept_map_each { }; +struct dept_map_commmon { }; struct dept_task { };

#define DEPT_TASK_INITIALIZER(t)

-#define dept_on() do { } while (0) -#define dept_off() do { } while (0) -#define dept_init() do { } while (0) -#define dept_task_init(t) do { } while (0) -#define dept_task_exit(t) do { } while (0) -#define dept_free_range(s, sz) do { } while (0) -#define dept_map_init(m, k, s, n) do { (void)(n); (void)(k); } while (0) -#define dept_map_reinit(m) do { } while (0) -#define dept_map_nocheck(m) do { } while (0) - -#define dept_wait(m, w_f, ip, w_fn, ne) do { (void)(w_fn); } while (0) -#define dept_stage_wait(m, w_f, w_fn, ne) do { (void)(w_fn); } while (0) -#define dept_ask_event_wait_commit(ip) do { } while (0) -#define dept_clean_stage() do { } while (0) -#define dept_ecxt_enter(m, e_f, ip, c_fn, e_fn, ne) do { (void)(c_fn); (void)(e_fn); } while (0) -#define dept_ask_event(m) do { } while (0) -#define dept_event(m, e_f, ip, e_fn) do { (void)(e_fn); } while (0) -#define dept_ecxt_exit(m, ip) do { } while (0) -#define dept_skip(m) do { } while (0) -#define dept_unskip_if_skipped(m) (false) -#define dept_key_init(k) do { (void)(k); } while (0) -#define dept_key_destroy(k) do { (void)(k); } while (0) +#define dept_on() do { } while (0) +#define dept_off() do { } while (0) +#define dept_init() do { } while (0) +#define dept_task_init(t) do { } while (0) +#define dept_task_exit(t) do { } while (0) +#define dept_free_range(s, sz) do { } while (0) +#define dept_map_init(m, k, s, n) do { (void)(n); (void)(k); } while (0) +#define dept_map_reinit(m) do { } while (0) +#define dept_map_nocheck(m) do { } while (0) + +#define dept_wait(m, w_f, ip, w_fn, ne) do { (void)(w_fn); } while (0) +#define dept_stage_wait(m, w_f, w_fn, ne) do { (void)(w_fn); } while (0) +#define dept_ask_event_wait_commit(ip) do { } while (0) +#define dept_clean_stage() do { } while (0) +#define dept_ecxt_enter(m, e_f, ip, c_fn, e_fn, ne) do { (void)(c_fn); (void)(e_fn); } while (0) +#define dept_ask_event(m) do { } while (0) +#define dept_event(m, e_f, ip, e_fn) do { (void)(e_fn); } while (0) +#define dept_ecxt_exit(m, ip) do { } while (0) +#define dept_skip(m) do { } while (0) +#define dept_unskip_if_skipped(m) (false) +#define dept_split_map_each_init(me) do { } while (0) +#define dept_split_map_common_init(mc, k, n) do { (void)(n); (void)(k); } while (0) +#define dept_wait_split_map(me, mc, ip, w_fn, ne) do { } while (0) +#define dept_event_split_map(me, mc, ip, e_fn) do { } while (0) +#define dept_ask_event_split_map(me, mc) do { } while (0) +#define dept_key_init(k) do { (void)(k); } while (0) +#define dept_key_destroy(k) do { (void)(k); } while (0) #endif #endif /* __LINUX_DEPT_H */ diff --git a/kernel/dependency/dept.c b/kernel/dependency/dept.c index 4142c78..6a47149 100644 --- a/kernel/dependency/dept.c +++ b/kernel/dependency/dept.c @@ -2325,6 +2325,128 @@ void dept_event(struct dept_map *m, unsigned long e_f, unsigned long ip, } EXPORT_SYMBOL_GPL(dept_event);

+void dept_split_map_each_init(struct dept_map_each *me) +{ + struct dept_task *dt = dept_task(); + unsigned long flags; + + if (READ_ONCE(dept_stop) || dt->recursive) + return; + + flags = dept_enter(); + + me->wgen = 0U; + + dept_exit(flags); +} +EXPORT_SYMBOL_GPL(dept_split_map_each_init); + +void dept_split_map_common_init(struct dept_map_common *mc, + struct dept_key *k, const char *n) +{ + struct dept_task *dt = dept_task(); + unsigned long flags; + + if (READ_ONCE(dept_stop) || dt->recursive) + return; + + flags = dept_enter(); + + if (mc->keys != k) + mc->keys = k; + clean_classes_cache(&mc->keys_local); + + /* + * sub_usr is not used with split map. + */ + mc->sub_usr = 0; + mc->name = n; + mc->nocheck = false; + + dept_exit(flags); +} +EXPORT_SYMBOL_GPL(dept_split_map_common_init); + +void dept_wait_split_map(struct dept_map_each *me, + struct dept_map_common *mc, + unsigned long ip, const char *w_fn, int ne) +{ + struct dept_task *dt = dept_task(); + struct dept_class *c; + struct dept_key *k; + unsigned long flags; + + if (READ_ONCE(dept_stop) || dt->recursive) + return; + + if (mc->nocheck) + return; + + flags = dept_enter(); + + k = mc->keys ?: &mc->keys_local; + c = check_new_class(&mc->keys_local, k, 0, mc->name); + if (c) + add_wait(c, ip, w_fn, ne); + + dept_exit(flags); +} +EXPORT_SYMBOL_GPL(dept_wait_split_map); + +void dept_ask_event_split_map(struct dept_map_each *me, + struct dept_map_common *mc) +{ + struct dept_task *dt = dept_task(); + unsigned long flags; + unsigned int wg; + + if (READ_ONCE(dept_stop) || dt->recursive) + return; + + if (mc->nocheck) + return; + + flags = dept_enter(); + + /* + * Avoid zero wgen. + */ + wg = atomic_inc_return(&wgen) ?: atomic_inc_return(&wgen); + WRITE_ONCE(me->wgen, wg); + + dept_exit(flags); +} +EXPORT_SYMBOL_GPL(dept_ask_event_split_map); + +void dept_event_split_map(struct dept_map_each *me, + struct dept_map_common *mc, + unsigned long ip, const char *e_fn) +{ + struct dept_task *dt = dept_task(); + struct dept_class *c; + struct dept_key *k; + unsigned long flags; + + if (READ_ONCE(dept_stop) || dt->recursive) + return; + + if (mc->nocheck) + return; + + flags = dept_enter(); + + k = mc->keys ?: &mc->keys_local; + c = check_new_class(&mc->keys_local, k, 0, mc->name); + if (c) { + add_ecxt((void *)me, c, 0UL, NULL, e_fn, 0); + do_event((void *)me, c, READ_ONCE(me->wgen), ip); + pop_ecxt((void *)me); + } + + dept_exit(flags); +} +EXPORT_SYMBOL_GPL(dept_event_split_map); + void dept_ecxt_exit(struct dept_map *m, unsigned long ip) { struct dept_task *dt = dept_task();

Makes SDT able to track dependencies by swait.

Signed-off-by: Byungchul Park byungchul.park@lge.com --- include/linux/swait.h | 4 ++++ kernel/sched/swait.c | 10 ++++++++++ 2 files changed, 14 insertions(+)

diff --git a/include/linux/swait.h b/include/linux/swait.h index 6a8c22b..dbdf2ce 100644 --- a/include/linux/swait.h +++ b/include/linux/swait.h @@ -6,6 +6,7 @@ #include <linux/stddef.h> #include <linux/spinlock.h> #include <linux/wait.h> +#include <linux/dept_sdt.h> #include <asm/current.h>

/* @@ -43,6 +44,7 @@ struct swait_queue_head { raw_spinlock_t lock; struct list_head task_list; + struct dept_map dmap; };

struct swait_queue { @@ -61,6 +63,7 @@ struct swait_queue { #define __SWAIT_QUEUE_HEAD_INITIALIZER(name) { \ .lock = __RAW_SPIN_LOCK_UNLOCKED(name.lock), \ .task_list = LIST_HEAD_INIT((name).task_list), \ + .dmap = DEPT_SDT_MAP_INIT(name), \ }

#define DECLARE_SWAIT_QUEUE_HEAD(name) \ @@ -72,6 +75,7 @@ extern void __init_swait_queue_head(struct swait_queue_head *q, const char *name #define init_swait_queue_head(q) \ do { \ static struct lock_class_key __key; \ + sdt_map_init(&(q)->dmap); \ __init_swait_queue_head((q), #q, &__key); \ } while (0)

diff --git a/kernel/sched/swait.c b/kernel/sched/swait.c index e1c655f..4ca7d6e 100644 --- a/kernel/sched/swait.c +++ b/kernel/sched/swait.c @@ -27,6 +27,7 @@ void swake_up_locked(struct swait_queue_head *q) return;

curr = list_first_entry(&q->task_list, typeof(*curr), task_list); + sdt_event(&q->dmap); wake_up_process(curr->task); list_del_init(&curr->task_list); } @@ -69,6 +70,7 @@ void swake_up_all(struct swait_queue_head *q) while (!list_empty(&tmp)) { curr = list_first_entry(&tmp, typeof(*curr), task_list);

+ sdt_event(&q->dmap); wake_up_state(curr->task, TASK_NORMAL); list_del_init(&curr->task_list);

@@ -97,6 +99,9 @@ void prepare_to_swait_exclusive(struct swait_queue_head *q, struct swait_queue * __prepare_to_swait(q, wait); set_current_state(state); raw_spin_unlock_irqrestore(&q->lock, flags); + + if (state & TASK_NORMAL) + sdt_wait_prepare(&q->dmap); } EXPORT_SYMBOL(prepare_to_swait_exclusive);

@@ -119,12 +124,16 @@ long prepare_to_swait_event(struct swait_queue_head *q, struct swait_queue *wait } raw_spin_unlock_irqrestore(&q->lock, flags);

+ if (!ret && state & TASK_NORMAL) + sdt_wait_prepare(&q->dmap); + return ret; } EXPORT_SYMBOL(prepare_to_swait_event);

void __finish_swait(struct swait_queue_head *q, struct swait_queue *wait) { + sdt_wait_finish(); __set_current_state(TASK_RUNNING); if (!list_empty(&wait->task_list)) list_del_init(&wait->task_list); @@ -134,6 +143,7 @@ void finish_swait(struct swait_queue_head *q, struct swait_queue *wait) { unsigned long flags;

+ sdt_wait_finish(); __set_current_state(TASK_RUNNING);

if (!list_empty_careful(&wait->task_list)) {

cb92173d1f0 (locking/lockdep, cpu/hotplug: Annotate AP thread) was introduced to make lockdep_assert_cpus_held() work in AP thread.

However, the annotation is too strong for that purpose. We don't have to use more than try lock annotation for that.

Furthermore, now that Dept was introduced, false positive alarms was reported by that. Replaced it with try lock annotation.

Signed-off-by: Byungchul Park byungchul.park@lge.com --- kernel/cpu.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/cpu.c b/kernel/cpu.c index 407a256..1f92a42 100644 --- a/kernel/cpu.c +++ b/kernel/cpu.c @@ -355,7 +355,7 @@ int lockdep_is_cpus_held(void)

static void lockdep_acquire_cpus_lock(void) { - rwsem_acquire(&cpu_hotplug_lock.dep_map, 0, 0, _THIS_IP_); + rwsem_acquire(&cpu_hotplug_lock.dep_map, 0, 1, _THIS_IP_); }

static void lockdep_release_cpus_lock(void)

Workqueue already provides concurrency control. By that, any wait in a work doesn't prevents events in other works with the control enabled. Thus, each work would better be considered a different context.

So let Dept assign a different context id to each work.

Signed-off-by: Byungchul Park byungchul.park@lge.com --- include/linux/dept.h | 2 ++ kernel/dependency/dept.c | 10 ++++++++++ kernel/workqueue.c | 3 +++ 3 files changed, 15 insertions(+)

diff --git a/include/linux/dept.h b/include/linux/dept.h index 1a1c307..55c5ed5 100644 --- a/include/linux/dept.h +++ b/include/linux/dept.h @@ -486,6 +486,7 @@ struct dept_task { extern void dept_event_split_map(struct dept_map_each *me, struct dept_map_common *mc, unsigned long ip, const char *e_fn); extern void dept_ask_event_split_map(struct dept_map_each *me, struct dept_map_common *mc); extern void dept_kernel_enter(void); +extern void dept_work_enter(void);

/* * for users who want to manage external keys @@ -527,6 +528,7 @@ struct dept_task { #define dept_event_split_map(me, mc, ip, e_fn) do { } while (0) #define dept_ask_event_split_map(me, mc) do { } while (0) #define dept_kernel_enter() do { } while (0) +#define dept_work_enter() do { } while (0) #define dept_key_init(k) do { (void)(k); } while (0) #define dept_key_destroy(k) do { (void)(k); } while (0) #endif diff --git a/kernel/dependency/dept.c b/kernel/dependency/dept.c index 8f962ae..5d4efc3 100644 --- a/kernel/dependency/dept.c +++ b/kernel/dependency/dept.c @@ -1873,6 +1873,16 @@ void dept_disable_hardirq(unsigned long ip) dept_exit(flags); }

+/* + * Assign a different context id to each work. + */ +void dept_work_enter(void) +{ + struct dept_task *dt = dept_task(); + + dt->cxt_id[DEPT_CXT_PROCESS] += (1UL << DEPT_CXTS_NR); +} + void dept_kernel_enter(void) { struct dept_task *dt = dept_task(); diff --git a/kernel/workqueue.c b/kernel/workqueue.c index 33f1106..f5d762c 100644 --- a/kernel/workqueue.c +++ b/kernel/workqueue.c @@ -51,6 +51,7 @@ #include <linux/sched/isolation.h> #include <linux/nmi.h> #include <linux/kvm_para.h> +#include <linux/dept.h>

#include "workqueue_internal.h"

@@ -2217,6 +2218,8 @@ static void process_one_work(struct worker *worker, struct work_struct *work)

lockdep_copy_map(&lockdep_map, &work->lockdep_map); #endif + dept_work_enter(); + /* ensure we're on the correct CPU */ WARN_ON_ONCE(!(pool->flags & POOL_DISASSOCIATED) && raw_smp_processor_id() != pool->cpu);

For completions who don't want to get tracked by Dept, added init_completion_nocheck() to disable Dept on it.

Signed-off-by: Byungchul Park byungchul.park@lge.com --- include/linux/completion.h | 14 +++++++++++--- 1 file changed, 11 insertions(+), 3 deletions(-)

diff --git a/include/linux/completion.h b/include/linux/completion.h index a1ad5a8..9bd3bc9 100644 --- a/include/linux/completion.h +++ b/include/linux/completion.h @@ -30,6 +30,7 @@ struct completion { };

#ifdef CONFIG_DEPT +#define dept_wfc_nocheck(m) dept_map_nocheck(m) #define dept_wfc_init(m, k, s, n) dept_map_init(m, k, s, n) #define dept_wfc_reinit(m) dept_map_reinit(m) #define dept_wfc_wait(m, ip) \ @@ -41,6 +42,7 @@ struct completion { #define dept_wfc_enter(m, ip) dept_ecxt_enter(m, 1UL, ip, "completion_context_enter", "complete", 0) #define dept_wfc_exit(m, ip) dept_ecxt_exit(m, ip) #else +#define dept_wfc_nocheck(m) do { } while (0) #define dept_wfc_init(m, k, s, n) do { (void)(n); (void)(k); } while (0) #define dept_wfc_reinit(m) do { } while (0) #define dept_wfc_wait(m, ip) do { } while (0) @@ -55,10 +57,11 @@ struct completion { #define WFC_DEPT_MAP_INIT(work) #endif

+#define init_completion_nocheck(x) __init_completion(x, NULL, #x, false) #define init_completion(x) \ do { \ static struct dept_key __dkey; \ - __init_completion(x, &__dkey, #x); \ + __init_completion(x, &__dkey, #x, true); \ } while (0)

#define init_completion_map(x, m) init_completion(x) @@ -117,10 +120,15 @@ static inline void complete_release(struct completion *x) {} */ static inline void __init_completion(struct completion *x, struct dept_key *dkey, - const char *name) + const char *name, bool check) { x->done = 0; - dept_wfc_init(&x->dmap, dkey, 0, name); + + if (check) + dept_wfc_init(&x->dmap, dkey, 0, name); + else + dept_wfc_nocheck(&x->dmap); + init_swait_queue_head(&x->wait); }

Dept already prevents creating dependencies between different depths of the class indicated by *_lock_nested() when the lock acquisitions happen consecutively.

lock A0 with depth lock_nested A1 with depth + 1 ... unlock A1 unlock A0

Dept does not create A0 -> A1 dependency in this case, either.

However, once another class cut in, the code becomes problematic. When Dept tries to create real dependencies, it does not only create real ones but also wrong ones between different depths of the class.

lock A0 with depth lock B lock_nested A1 with depth + 1 ... unlock A1 unlock B unlock A0

Even in this case, Dept should not create A0 -> A1 dependency.

So let Dept not create wrong dependencies between different depths of the class in any case.

Reported-by: 42.hyeyoo@gmail.com Signed-off-by: Byungchul Park byungchul.park@lge.com --- kernel/dependency/dept.c | 9 +-------- 1 file changed, 1 insertion(+), 8 deletions(-)

diff --git a/kernel/dependency/dept.c b/kernel/dependency/dept.c index 5d4efc3..cc1b3a3 100644 --- a/kernel/dependency/dept.c +++ b/kernel/dependency/dept.c @@ -1458,14 +1458,7 @@ static void add_wait(struct dept_class *c, unsigned long ip,

eh = dt->ecxt_held + i; if (eh->ecxt->class != c || eh->nest == ne) - break; - } - - for (; i >= 0; i--) { - struct dept_ecxt_held *eh; - - eh = dt->ecxt_held + i; - add_dep(eh->ecxt, w); + add_dep(eh->ecxt, w); }

if (!wait_consumed(w) && !rich_stack) {

Dept works with waits preceeding an event, that might lead a deadlock. Once the event has been handled, it's hard to ensure further waits actually contibute to deadlock until next turn, which will start when a sleep associated with that map happens.

So let Dept start tracking dependency when a sleep happens and stop tracking dependency once the event e.i. wake up, has been handled.

Signed-off-by: Byungchul Park byungchul.park@lge.com --- kernel/dependency/dept.c | 11 +++++++++++ 1 file changed, 11 insertions(+)

diff --git a/kernel/dependency/dept.c b/kernel/dependency/dept.c index cc1b3a3..1c91db8 100644 --- a/kernel/dependency/dept.c +++ b/kernel/dependency/dept.c @@ -2325,6 +2325,12 @@ void dept_event(struct dept_map *m, unsigned long e_f, unsigned long ip, do_event((void *)m, c, READ_ONCE(m->wgen), ip); pop_ecxt((void *)m); } + + /* + * Keep the map diabled until the next sleep. + */ + WRITE_ONCE(m->wgen, 0); + dept_exit(flags); } EXPORT_SYMBOL_GPL(dept_event); @@ -2447,6 +2453,11 @@ void dept_event_split_map(struct dept_map_each *me, pop_ecxt((void *)me); }

+ /* + * Keep the map diabled until the next sleep. + */ + WRITE_ONCE(me->wgen, 0); + dept_exit(flags); } EXPORT_SYMBOL_GPL(dept_event_split_map);