Hi all,
My bad for the resend. Adding cc: intel-gfx, and the maintainers and mailing lists for include/drm/drm_file.h.
Following a discussion on the patch ("drm: use the lookup lock in drm_is_current_master") [1], Peter Zijlstra proposed new lockdep_assert helpers to make it convenient to compose lockdep checks together.
This series includes the patch that introduces the new lockdep helpers, then utilizes these helpers in drm_is_current_master_locked in the following patch.
v1 -> v2: Patch 2: - Updated the kerneldoc on the lock design of drm_file.master to explain the use of lockdep_assert(). As suggested by Boqun Feng.
Link: https://lore.kernel.org/lkml/20210722092929.244629-2-desmondcheongzx@gmail.c... [1]
Best wishes, Desmond
Desmond Cheong Zhi Xi (1): drm: add lockdep assert to drm_is_current_master_locked
Peter Zijlstra (1): locking/lockdep: Provide lockdep_assert{,_once}() helpers
drivers/gpu/drm/drm_auth.c | 6 +++--- include/drm/drm_file.h | 4 ++++ include/linux/lockdep.h | 41 +++++++++++++++++++------------------- 3 files changed, 28 insertions(+), 23 deletions(-)
From: Peter Zijlstra peterz@infradead.org
Extract lockdep_assert{,_once}() helpers to more easily write composite assertions like, for example:
lockdep_assert(lockdep_is_held(&drm_device.master_mutex) || lockdep_is_held(&drm_file.master_lookup_lock));
Signed-off-by: Peter Zijlstra (Intel) peterz@infradead.org Signed-off-by: Desmond Cheong Zhi Xi desmondcheongzx@gmail.com Acked-by: Boqun Feng boqun.feng@gmail.com Acked-by: Waiman Long longman@redhat.com Acked-by: Peter Zijlstra (Intel) peterz@infradead.org --- include/linux/lockdep.h | 41 +++++++++++++++++++++-------------------- 1 file changed, 21 insertions(+), 20 deletions(-)
diff --git a/include/linux/lockdep.h b/include/linux/lockdep.h index 5cf387813754..9fe165beb0f9 100644 --- a/include/linux/lockdep.h +++ b/include/linux/lockdep.h @@ -306,31 +306,29 @@ extern void lock_unpin_lock(struct lockdep_map *lock, struct pin_cookie);
#define lockdep_depth(tsk) (debug_locks ? (tsk)->lockdep_depth : 0)
-#define lockdep_assert_held(l) do { \ - WARN_ON(debug_locks && \ - lockdep_is_held(l) == LOCK_STATE_NOT_HELD); \ - } while (0) +#define lockdep_assert(cond) \ + do { WARN_ON(debug_locks && !(cond)); } while (0)
-#define lockdep_assert_not_held(l) do { \ - WARN_ON(debug_locks && \ - lockdep_is_held(l) == LOCK_STATE_HELD); \ - } while (0) +#define lockdep_assert_once(cond) \ + do { WARN_ON_ONCE(debug_locks && !(cond)); } while (0)
-#define lockdep_assert_held_write(l) do { \ - WARN_ON(debug_locks && !lockdep_is_held_type(l, 0)); \ - } while (0) +#define lockdep_assert_held(l) \ + lockdep_assert(lockdep_is_held(l) != LOCK_STATE_NOT_HELD)
-#define lockdep_assert_held_read(l) do { \ - WARN_ON(debug_locks && !lockdep_is_held_type(l, 1)); \ - } while (0) +#define lockdep_assert_not_held(l) \ + lockdep_assert(lockdep_is_held(l) != LOCK_STATE_HELD)
-#define lockdep_assert_held_once(l) do { \ - WARN_ON_ONCE(debug_locks && !lockdep_is_held(l)); \ - } while (0) +#define lockdep_assert_held_write(l) \ + lockdep_assert(lockdep_is_held_type(l, 0))
-#define lockdep_assert_none_held_once() do { \ - WARN_ON_ONCE(debug_locks && current->lockdep_depth); \ - } while (0) +#define lockdep_assert_held_read(l) \ + lockdep_assert(lockdep_is_held_type(l, 1)) + +#define lockdep_assert_held_once(l) \ + lockdep_assert_once(lockdep_is_held(l) != LOCK_STATE_NOT_HELD) + +#define lockdep_assert_none_held_once() \ + lockdep_assert_once(!current->lockdep_depth)
#define lockdep_recursing(tsk) ((tsk)->lockdep_recursion)
@@ -407,6 +405,9 @@ extern int lock_is_held(const void *); extern int lockdep_is_held(const void *); #define lockdep_is_held_type(l, r) (1)
+#define lockdep_assert(c) do { } while (0) +#define lockdep_assert_once(c) do { } while (0) + #define lockdep_assert_held(l) do { (void)(l); } while (0) #define lockdep_assert_not_held(l) do { (void)(l); } while (0) #define lockdep_assert_held_write(l) do { (void)(l); } while (0)
In drm_is_current_master_locked, accessing drm_file.master should be protected by either drm_file.master_lookup_lock or drm_device.master_mutex. This was previously awkward to assert with lockdep.
Following patch ("locking/lockdep: Provide lockdep_assert{,_once}() helpers"), this assertion is now convenient. So we add in the assertion and explain this lock design in the kerneldoc.
Signed-off-by: Desmond Cheong Zhi Xi desmondcheongzx@gmail.com Acked-by: Boqun Feng boqun.feng@gmail.com Acked-by: Waiman Long longman@redhat.com Acked-by: Peter Zijlstra (Intel) peterz@infradead.org --- drivers/gpu/drm/drm_auth.c | 6 +++--- include/drm/drm_file.h | 4 ++++ 2 files changed, 7 insertions(+), 3 deletions(-)
diff --git a/drivers/gpu/drm/drm_auth.c b/drivers/gpu/drm/drm_auth.c index 9c24b8cc8e36..6f4d7ff23c80 100644 --- a/drivers/gpu/drm/drm_auth.c +++ b/drivers/gpu/drm/drm_auth.c @@ -63,9 +63,9 @@
static bool drm_is_current_master_locked(struct drm_file *fpriv) { - /* Either drm_device.master_mutex or drm_file.master_lookup_lock - * should be held here. - */ + lockdep_assert_once(lockdep_is_held(&fpriv->master_lookup_lock) || + lockdep_is_held(&fpriv->minor->dev->master_mutex)); + return fpriv->is_master && drm_lease_owner(fpriv->master) == fpriv->minor->dev->master; }
diff --git a/include/drm/drm_file.h b/include/drm/drm_file.h index 726cfe0ff5f5..a3acb7ac3550 100644 --- a/include/drm/drm_file.h +++ b/include/drm/drm_file.h @@ -233,6 +233,10 @@ struct drm_file { * this only matches &drm_device.master if the master is the currently * active one. * + * To update @master, both &drm_device.master_mutex and + * @master_lookup_lock need to be held, therefore holding either of + * them is safe and enough for the read side. + * * When dereferencing this pointer, either hold struct * &drm_device.master_mutex for the duration of the pointer's use, or * use drm_file_get_master() if struct &drm_device.master_mutex is not
On Mon, Aug 02, 2021 at 06:59:57PM +0800, Desmond Cheong Zhi Xi wrote:
In drm_is_current_master_locked, accessing drm_file.master should be protected by either drm_file.master_lookup_lock or drm_device.master_mutex. This was previously awkward to assert with lockdep.
Following patch ("locking/lockdep: Provide lockdep_assert{,_once}() helpers"), this assertion is now convenient. So we add in the assertion and explain this lock design in the kerneldoc.
Signed-off-by: Desmond Cheong Zhi Xi desmondcheongzx@gmail.com Acked-by: Boqun Feng boqun.feng@gmail.com Acked-by: Waiman Long longman@redhat.com Acked-by: Peter Zijlstra (Intel) peterz@infradead.org
Both patches pushed to drm-misc-next, thanks. -Daniel
drivers/gpu/drm/drm_auth.c | 6 +++--- include/drm/drm_file.h | 4 ++++ 2 files changed, 7 insertions(+), 3 deletions(-)
diff --git a/drivers/gpu/drm/drm_auth.c b/drivers/gpu/drm/drm_auth.c index 9c24b8cc8e36..6f4d7ff23c80 100644 --- a/drivers/gpu/drm/drm_auth.c +++ b/drivers/gpu/drm/drm_auth.c @@ -63,9 +63,9 @@
static bool drm_is_current_master_locked(struct drm_file *fpriv) {
- /* Either drm_device.master_mutex or drm_file.master_lookup_lock
* should be held here.*/
- lockdep_assert_once(lockdep_is_held(&fpriv->master_lookup_lock) ||
lockdep_is_held(&fpriv->minor->dev->master_mutex));- return fpriv->is_master && drm_lease_owner(fpriv->master) == fpriv->minor->dev->master;
}
diff --git a/include/drm/drm_file.h b/include/drm/drm_file.h index 726cfe0ff5f5..a3acb7ac3550 100644 --- a/include/drm/drm_file.h +++ b/include/drm/drm_file.h @@ -233,6 +233,10 @@ struct drm_file { * this only matches &drm_device.master if the master is the currently * active one. *
* To update @master, both &drm_device.master_mutex and* @master_lookup_lock need to be held, therefore holding either of* them is safe and enough for the read side.*
- When dereferencing this pointer, either hold struct
- &drm_device.master_mutex for the duration of the pointer's use, or
- use drm_file_get_master() if struct &drm_device.master_mutex is not
-- 2.25.1
dri-devel@lists.freedesktop.org
-
Daniel Vetter -
Desmond Cheong Zhi Xi