5.4-stable review patch. If anyone has any objections, please let me know.
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From: Christian König christian.koenig@amd.com
[ 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@amd.com Reviewed-by: Daniel Vetter daniel.vetter@ffwll.ch Acked-by: Peter Zijlstra (Intel) peterz@infradead.org 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@kernel.org --- drivers/gpu/drm/drm_syncobj.c | 12 ++++++++++++ include/linux/lockdep.h | 5 +++++ 2 files changed, 17 insertions(+)
diff --git a/drivers/gpu/drm/drm_syncobj.c b/drivers/gpu/drm/drm_syncobj.c index 8b155e3377cfe..a1d2a3dc00768 100644 --- a/drivers/gpu/drm/drm_syncobj.c +++ b/drivers/gpu/drm/drm_syncobj.c @@ -325,6 +325,15 @@ 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) { @@ -889,6 +898,9 @@ 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 b8a835fd611b2..15d92abb3f2d8 100644 --- a/include/linux/lockdep.h +++ b/include/linux/lockdep.h @@ -403,6 +403,10 @@ 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) @@ -479,6 +483,7 @@ struct lockdep_map { }; #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)