This is a note to let you know that I've just added the patch titled
drm/syncobj: make lockdep complain on WAIT_FOR_SUBMIT v3
to the 5.10-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
drm-syncobj-make-lockdep-complain-on-wait_for_submit.patch
and it can be found in the queue-5.10 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
commit f2191e653330dbf2c480af1b1a1e231723da7f3e
Author: Christian König <christian.koenig@xxxxxxx>
Date: Fri Jan 15 14:32:39 2021 +0100
drm/syncobj: make lockdep complain on WAIT_FOR_SUBMIT v3
[ Upstream commit 7621350c6bb20fb6ab7eb988833ab96eac3dcbef ]
DRM_SYNCOBJ_WAIT_FLAGS_WAIT_FOR_SUBMIT can't be used when we hold locks
since we are basically waiting for userspace to do something.
Holding a lock while doing so can trivial deadlock with page faults
etc...
So make lockdep complain when a driver tries to do this.
v2: Add lockdep_assert_none_held() macro.
v3: Add might_sleep() and also use lockdep_assert_none_held() in the
IOCTL path.
Signed-off-by: Christian König <christian.koenig@xxxxxxx>
Reviewed-by: Daniel Vetter <daniel.vetter@xxxxxxxx>
Acked-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
Link: https://patchwork.freedesktop.org/patch/414944/
Stable-dep-of: 3c43177ffb54 ("drm/syncobj: call drm_syncobj_fence_add_wait when WAIT_AVAILABLE flag is set")
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
diff --git a/drivers/gpu/drm/drm_syncobj.c b/drivers/gpu/drm/drm_syncobj.c
index 738e60139db90..4c3c8f8da0215 100644
--- a/drivers/gpu/drm/drm_syncobj.c
+++ b/drivers/gpu/drm/drm_syncobj.c
@@ -387,6 +387,15 @@ int drm_syncobj_find_fence(struct drm_file *file_private,
if (!syncobj)
return -ENOENT;
+ /* Waiting for userspace with locks help is illegal cause that can
+ * trivial deadlock with page faults for example. Make lockdep complain
+ * about it early on.
+ */
+ if (flags & DRM_SYNCOBJ_WAIT_FLAGS_WAIT_FOR_SUBMIT) {
+ might_sleep();
+ lockdep_assert_none_held_once();
+ }
+
*fence = drm_syncobj_fence_get(syncobj);
if (*fence) {
@@ -951,6 +960,9 @@ static signed long drm_syncobj_array_wait_timeout(struct drm_syncobj **syncobjs,
uint64_t *points;
uint32_t signaled_count, i;
+ if (flags & DRM_SYNCOBJ_WAIT_FLAGS_WAIT_FOR_SUBMIT)
+ lockdep_assert_none_held_once();
+
points = kmalloc_array(count, sizeof(*points), GFP_KERNEL);
if (points == NULL)
return -ENOMEM;
diff --git a/include/linux/lockdep.h b/include/linux/lockdep.h
index 2c2586312b447..3eca9f91b9a56 100644
--- a/include/linux/lockdep.h
+++ b/include/linux/lockdep.h
@@ -321,6 +321,10 @@ extern void lock_unpin_lock(struct lockdep_map *lock, struct pin_cookie);
WARN_ON_ONCE(debug_locks && !lockdep_is_held(l)); \
} while (0)
+#define lockdep_assert_none_held_once() do { \
+ WARN_ON_ONCE(debug_locks && current->lockdep_depth); \
+ } while (0)
+
#define lockdep_recursing(tsk) ((tsk)->lockdep_recursion)
#define lockdep_pin_lock(l) lock_pin_lock(&(l)->dep_map)
@@ -394,6 +398,7 @@ static inline void lockdep_unregister_key(struct lock_class_key *key)
#define lockdep_assert_held_write(l) do { (void)(l); } while (0)
#define lockdep_assert_held_read(l) do { (void)(l); } while (0)
#define lockdep_assert_held_once(l) do { (void)(l); } while (0)
+#define lockdep_assert_none_held_once() do { } while (0)
#define lockdep_recursing(tsk) (0)
