From: Sean Paul seanpaul@chromium.org
This patch adds a new module parameter called drm.trace which accepts the same mask as drm.debug. When a debug category is enabled, log messages will be put in a new tracefs instance called drm for consumption.
Using the new tracefs instance will allow distros to enable drm logging in production without impacting performance or spamming the system logs.
Cc: Daniel Vetter daniel.vetter@ffwll.ch Cc: David Airlie airlied@gmail.com Cc: Jani Nikula jani.nikula@linux.intel.com Cc: Joonas Lahtinen joonas.lahtinen@linux.intel.com Cc: Pekka Paalanen ppaalanen@gmail.com Cc: Rob Clark robdclark@gmail.com Cc: Steven Rostedt rostedt@goodmis.org Cc: Thomas Zimmermann tzimmermann@suse.de Cc: Ville Syrjälä ville.syrjala@linux.intel.com Cc: Chris Wilson chris@chris-wilson.co.uk Cc: Steven Rostedt rostedt@goodmis.org Signed-off-by: Sean Paul seanpaul@chromium.org Link: https://patchwork.freedesktop.org/patch/msgid/20191010204823.195540-1-sean@p... #v1 Link: https://lists.freedesktop.org/archives/dri-devel/2019-November/243230.html #v2 Link: https://patchwork.freedesktop.org/patch/msgid/20191212203301.142437-1-sean@p... #v3 Link: https://patchwork.freedesktop.org/patch/msgid/20200114172155.215463-1-sean@p... #v4
Changes in v5: -Re-write to use trace_array and the tracefs instance support
Changes in v6: -Fix old-style function definition warnings Reported-by: kernel test robot lkp@intel.com --- Documentation/gpu/drm-uapi.rst | 6 + drivers/gpu/drm/drm_drv.c | 3 + drivers/gpu/drm/drm_print.c | 209 ++++++++++++++++++++++++++++----- include/drm/drm_print.h | 63 ++++++++-- 4 files changed, 241 insertions(+), 40 deletions(-)
diff --git a/Documentation/gpu/drm-uapi.rst b/Documentation/gpu/drm-uapi.rst index 56fec6ed1ad8..1c1c4d043f40 100644 --- a/Documentation/gpu/drm-uapi.rst +++ b/Documentation/gpu/drm-uapi.rst @@ -312,6 +312,12 @@ Debugfs Support .. kernel-doc:: drivers/gpu/drm/drm_debugfs.c :export:
+DRM Tracing +--------------- + +.. kernel-doc:: drivers/gpu/drm/drm_print.c + :doc: DRM Tracing + Sysfs Support =============
diff --git a/drivers/gpu/drm/drm_drv.c b/drivers/gpu/drm/drm_drv.c index bc38322f306e..88404af74c9b 100644 --- a/drivers/gpu/drm/drm_drv.c +++ b/drivers/gpu/drm/drm_drv.c @@ -1108,12 +1108,15 @@ static void drm_core_exit(void) drm_sysfs_destroy(); idr_destroy(&drm_minors_idr); drm_connector_ida_destroy(); + drm_trace_cleanup(); }
static int __init drm_core_init(void) { int ret;
+ drm_trace_init(); + drm_connector_ida_init(); idr_init(&drm_minors_idr);
diff --git a/drivers/gpu/drm/drm_print.c b/drivers/gpu/drm/drm_print.c index 4d984a01b3a3..18dfbd43c23b 100644 --- a/drivers/gpu/drm/drm_print.c +++ b/drivers/gpu/drm/drm_print.c @@ -31,6 +31,7 @@ #include <linux/moduleparam.h> #include <linux/seq_file.h> #include <linux/slab.h> +#include <linux/trace.h>
#include <drm/drm.h> #include <drm/drm_drv.h> @@ -43,17 +44,34 @@ unsigned int __drm_debug_syslog; EXPORT_SYMBOL(__drm_debug_syslog);
-MODULE_PARM_DESC(debug, "Enable debug output, where each bit enables a debug category.\n" -"\t\tBit 0 (0x01) will enable CORE messages (drm core code)\n" -"\t\tBit 1 (0x02) will enable DRIVER messages (drm controller code)\n" -"\t\tBit 2 (0x04) will enable KMS messages (modesetting code)\n" -"\t\tBit 3 (0x08) will enable PRIME messages (prime code)\n" -"\t\tBit 4 (0x10) will enable ATOMIC messages (atomic code)\n" -"\t\tBit 5 (0x20) will enable VBL messages (vblank code)\n" -"\t\tBit 7 (0x80) will enable LEASE messages (leasing code)\n" -"\t\tBit 8 (0x100) will enable DP messages (displayport code)"); +/* + * __drm_debug_trace: Enable debug output in drm tracing instance. + * Bitmask of DRM_UT_x. See include/drm/drm_print.h for details. + */ +unsigned int __drm_debug_trace; +EXPORT_SYMBOL(__drm_debug_trace); + +#define DEBUG_PARM_DESC(dst) \ +"Enable debug output to " dst ", where each bit enables a debug category.\n" \ +"\t\tBit 0 (0x01) will enable CORE messages (drm core code)\n" \ +"\t\tBit 1 (0x02) will enable DRIVER messages (drm controller code)\n" \ +"\t\tBit 2 (0x04) will enable KMS messages (modesetting code)\n" \ +"\t\tBit 3 (0x08) will enable PRIME messages (prime code)\n" \ +"\t\tBit 4 (0x10) will enable ATOMIC messages (atomic code)\n" \ +"\t\tBit 5 (0x20) will enable VBL messages (vblank code)\n" \ +"\t\tBit 7 (0x80) will enable LEASE messages (leasing code)\n" \ +"\t\tBit 8 (0x100) will enable DP messages (displayport code)" + +MODULE_PARM_DESC(debug, DEBUG_PARM_DESC("syslog")); module_param_named(debug, __drm_debug_syslog, int, 0600);
+MODULE_PARM_DESC(trace, DEBUG_PARM_DESC("tracefs")); +module_param_named(trace, __drm_debug_trace, int, 0600); + +#ifdef CONFIG_TRACING +struct trace_array *trace_arr; +#endif + void __drm_puts_coredump(struct drm_printer *p, const char *str) { struct drm_print_iterator *iterator = p->arg; @@ -166,6 +184,20 @@ void __drm_printfn_debug_syslog(struct drm_printer *p, struct va_format *vaf) } EXPORT_SYMBOL(__drm_printfn_debug_syslog);
+void __drm_printfn_trace(struct drm_printer *p, struct va_format *vaf) +{ + drm_trace_printf("%s %pV", p->prefix, vaf); +} +EXPORT_SYMBOL(__drm_printfn_trace); + +void __drm_printfn_debug_syslog_and_trace(struct drm_printer *p, + struct va_format *vaf) +{ + pr_debug("%s %pV", p->prefix, vaf); + drm_trace_printf("%s %pV", p->prefix, vaf); +} +EXPORT_SYMBOL(__drm_printfn_debug_syslog_and_trace); + void __drm_printfn_err(struct drm_printer *p, struct va_format *vaf) { pr_err("*ERROR* %s %pV", p->prefix, vaf); @@ -246,6 +278,14 @@ void drm_dev_printk(const struct device *dev, const char *level, struct va_format vaf; va_list args;
+ va_start(args, format); + vaf.fmt = format; + vaf.va = &args; + drm_trace_printf("%s%s[" DRM_NAME ":%ps] %pV", + dev ? dev_name(dev) : "",dev ? " " : "", + __builtin_return_address(0), &vaf); + va_end(args); + va_start(args, format); vaf.fmt = format; vaf.va = &args; @@ -267,21 +307,30 @@ void drm_dev_dbg(const struct device *dev, enum drm_debug_category category, struct va_format vaf; va_list args;
- if (!drm_debug_enabled(category)) - return; + if (drm_debug_syslog_enabled(category)) { + va_start(args, format); + vaf.fmt = format; + vaf.va = &args;
- va_start(args, format); - vaf.fmt = format; - vaf.va = &args; + if (dev) + dev_printk(KERN_DEBUG, dev, "[" DRM_NAME ":%ps] %pV", + __builtin_return_address(0), &vaf); + else + printk(KERN_DEBUG "[" DRM_NAME ":%ps] %pV", + __builtin_return_address(0), &vaf);
- if (dev) - dev_printk(KERN_DEBUG, dev, "[" DRM_NAME ":%ps] %pV", - __builtin_return_address(0), &vaf); - else - printk(KERN_DEBUG "[" DRM_NAME ":%ps] %pV", - __builtin_return_address(0), &vaf); + va_end(args); + }
- va_end(args); + if (drm_debug_trace_enabled(category)) { + va_start(args, format); + vaf.fmt = format; + vaf.va = &args; + drm_trace_printf("%s%s[" DRM_NAME ":%ps] %pV", + dev ? dev_name(dev) : "", dev ? " " : "", + __builtin_return_address(0), &vaf); + va_end(args); + } } EXPORT_SYMBOL(drm_dev_dbg);
@@ -290,17 +339,25 @@ void __drm_dbg(enum drm_debug_category category, const char *format, ...) struct va_format vaf; va_list args;
- if (!drm_debug_enabled(category)) - return; + if (drm_debug_syslog_enabled(category)) { + va_start(args, format); + vaf.fmt = format; + vaf.va = &args;
- va_start(args, format); - vaf.fmt = format; - vaf.va = &args; + printk(KERN_DEBUG "[" DRM_NAME ":%ps] %pV", + __builtin_return_address(0), &vaf);
- printk(KERN_DEBUG "[" DRM_NAME ":%ps] %pV", - __builtin_return_address(0), &vaf); + va_end(args); + }
- va_end(args); + if (drm_debug_trace_enabled(category)) { + va_start(args, format); + vaf.fmt = format; + vaf.va = &args; + drm_trace_printf("[" DRM_NAME ":%ps] %pV", + __builtin_return_address(0), &vaf); + va_end(args); + } } EXPORT_SYMBOL(__drm_dbg);
@@ -347,3 +404,97 @@ void drm_print_regset32(struct drm_printer *p, struct debugfs_regset32 *regset) } } EXPORT_SYMBOL(drm_print_regset32); + + +/** + * DOC: DRM Tracing + * + * *tl;dr* DRM tracing is a lightweight alternative to traditional DRM debug + * logging. + * + * While DRM logging is quite convenient when reproducing a specific issue, it + * doesn't help when something goes wrong unexpectedly. There are a couple + * reasons why one does not want to enable DRM logging at all times: + * + * 1. We don't want to overwhelm syslog with drm spam, others have to use it too + * 2. Console logging is slow + * + * DRM tracing aims to solve both these problems. + * + * To use DRM tracing, set the drm.trace module parameter (via cmdline or sysfs) + * to a DRM debug category mask (this is a bitmask of &drm_debug_category + * values): + * :: + * + * eg: echo 0x106 > /sys/module/drm/parameters/trace + * + * Once active, all log messages in the specified categories will be written to + * the DRM trace. Once at capacity, the trace will overwrite old messages with + * new ones. At any point, one can read the trace file to extract the previous N + * DRM messages: + * :: + * + * eg: cat /sys/kernel/tracing/instances/drm/trace + * + * Considerations + * ************** + * The trace is subsystem wide, so if you have multiple devices active, they + * will be adding logs to the same trace. + * + * The contents of the DRM Trace are **not** considered UABI. **DO NOT depend on + * the values of these traces in your userspace.** These traces are intended for + * entertainment purposes only. The contents of these logs carry no warranty, + * expressed or implied. + */ + + +#ifdef CONFIG_TRACING + +/** + * drm_trace_init - initializes the drm trace array + * + * This function fetches (or creates) the drm trace array. This should be called + * once on drm subsystem creation and matched with drm_trace_cleanup(). + */ +void drm_trace_init(void) +{ + trace_arr = trace_array_get_by_name("drm"); + if (!trace_arr) + return; +} +EXPORT_SYMBOL(drm_trace_init); + +/** + * drm_trace_printf - adds an entry to the drm tracefs instance + * @format: printf format of the message to add to the trace + * + * This function adds a new entry in the drm tracefs instance + */ +void drm_trace_printf(const char *format, ...) +{ + struct va_format vaf; + va_list args; + + va_start(args, format); + vaf.fmt = format; + vaf.va = &args; + trace_array_printk(trace_arr, _THIS_IP_, "%pV", &vaf); + va_end(args); +} + +/** + * drm_trace_cleanup - destroys the drm trace array + * + * This function destroys the drm trace array created with drm_trace_init. This + * should be called once on drm subsystem close and matched with + * drm_trace_init(). + */ +void drm_trace_cleanup(void) +{ + if (trace_arr) { + trace_array_put(trace_arr); + trace_array_destroy(trace_arr); + } +} +EXPORT_SYMBOL(drm_trace_cleanup); +#endif diff --git a/include/drm/drm_print.h b/include/drm/drm_print.h index 8987b98bbfda..284f7d325056 100644 --- a/include/drm/drm_print.h +++ b/include/drm/drm_print.h @@ -36,12 +36,13 @@
/* Do *not* use outside of drm_print.[ch]! */ extern unsigned int __drm_debug_syslog; +extern unsigned int __drm_debug_trace;
/** * DOC: print * * A simple wrapper for dev_printk(), seq_printf(), etc. Allows same - * debug code to be used for both debugfs and printk logging. + * debug code to be used for debugfs, printk and tracefs logging. * * For example:: * @@ -86,6 +87,9 @@ void __drm_printfn_seq_file(struct drm_printer *p, struct va_format *vaf); void __drm_puts_seq_file(struct drm_printer *p, const char *str); void __drm_printfn_info(struct drm_printer *p, struct va_format *vaf); void __drm_printfn_debug_syslog(struct drm_printer *p, struct va_format *vaf); +void __drm_printfn_trace(struct drm_printer *p, struct va_format *vaf); +void __drm_printfn_debug_syslog_and_trace(struct drm_printer *p, + struct va_format *vaf); void __drm_printfn_err(struct drm_printer *p, struct va_format *vaf); void __drm_printfn_noop(struct drm_printer *p, struct va_format *vaf);
@@ -219,7 +223,8 @@ static inline struct drm_printer drm_info_printer(struct device *dev) }
/** - * drm_debug_printer - construct a &drm_printer that outputs to pr_debug() + * drm_debug_printer - construct a &drm_printer that outputs to pr_debug() and + * drm tracefs * @prefix: debug output prefix * * RETURNS: @@ -228,7 +233,7 @@ static inline struct drm_printer drm_info_printer(struct device *dev) static inline struct drm_printer drm_debug_printer(const char *prefix) { struct drm_printer p = { - .printfn = __drm_printfn_debug_syslog, + .printfn = __drm_printfn_debug_syslog_and_trace, .prefix = prefix }; return p; @@ -254,14 +259,14 @@ static inline struct drm_printer drm_err_printer(const char *prefix) * enum drm_debug_category - The DRM debug categories * * Each of the DRM debug logging macros use a specific category, and the logging - * is filtered by the drm.debug module parameter. This enum specifies the values - * for the interface. + * is filtered by the drm.debug and drm.trace module parameters. This enum + * specifies the values for the interface. * * Each DRM_DEBUG_<CATEGORY> macro logs to DRM_UT_<CATEGORY> category, except * DRM_DEBUG() logs to DRM_UT_CORE. * - * Enabling verbose debug messages is done through the drm.debug parameter, each - * category being enabled by a bit: + * Enabling verbose debug messages is done through the drm.debug and drm.trace + * parameters, each category being enabled by a bit: * * - drm.debug=0x1 will enable CORE messages * - drm.debug=0x2 will enable DRIVER messages @@ -270,10 +275,14 @@ static inline struct drm_printer drm_err_printer(const char *prefix) * - drm.debug=0x1ff will enable all messages * * An interesting feature is that it's possible to enable verbose logging at - * run-time by echoing the debug value in its sysfs node:: + * run-time by echoing the debug category value in its sysfs node:: * + * # For syslog logging: * # echo 0xf > /sys/module/drm/parameters/debug * + * # For tracefs logging: + * # echo 0xf > /sys/module/drm/parameters/trace + * */ enum drm_debug_category { /** @@ -325,14 +334,20 @@ static inline bool drm_debug_syslog_enabled(enum drm_debug_category category) return unlikely(__drm_debug_syslog & category); }
+static inline bool drm_debug_trace_enabled(enum drm_debug_category category) +{ + return unlikely(__drm_debug_trace & category); +} + static inline bool drm_debug_enabled(enum drm_debug_category category) { - return drm_debug_syslog_enabled(category); + return drm_debug_syslog_enabled(category) || + drm_debug_trace_enabled(category); }
/** * drm_debug_category_printer - construct a &drm_printer that outputs to - * pr_debug() if enabled for the given category. + * pr_debug() and/or the drm tracefs instance if enabled for the given category. * @category: the DRM_UT_* message category this message belongs to * @prefix: trace output prefix * @@ -347,8 +362,13 @@ drm_debug_category_printer(enum drm_debug_category category, .prefix = prefix };
- if (drm_debug_syslog_enabled(category)) { + if (drm_debug_syslog_enabled(category) && + drm_debug_trace_enabled(category)) { + p.printfn = __drm_printfn_debug_syslog_and_trace; + } else if (drm_debug_syslog_enabled(category)) { p.printfn = __drm_printfn_debug_syslog; + } else if (drm_debug_trace_enabled(category)) { + p.printfn = __drm_printfn_trace; } else { WARN(1, "Debug category %d is inactive.", category); p.printfn = __drm_printfn_noop; @@ -357,6 +377,27 @@ drm_debug_category_printer(enum drm_debug_category category, return p; }
+ +#ifdef CONFIG_TRACING +void drm_trace_init(void); +__printf(1, 2) +void drm_trace_printf(const char *format, ...); +void drm_trace_cleanup(void); +#else +static inline void drm_trace_init(void) +{ +} + +__printf(1, 2) +static inline void drm_trace_printf(const char *format, ...) +{ +} + +static inline void drm_trace_cleanup(void) +{ +} +#endif + /* * struct device based logging *