5.4-stable review patch. If anyone has any objections, please let me know.
------------------
From: Christian König <christian.koenig@xxxxxxx>
[ 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>
---
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)
--
2.43.0
