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>
---
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 6e74e6745eca..9ecfec1e5567 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);
drm_syncobj_put(syncobj);
@@ -940,6 +949,9 @@ 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 b9e9adec73e8..6eb117c0d0f3 100644
--- a/include/linux/lockdep.h
+++ b/include/linux/lockdep.h
@@ -310,6 +310,10 @@ 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)
@@ -387,6 +391,7 @@ extern int lockdep_is_held(const void *);
#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)
--
2.25.1
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