Commit 7621350c authored by Christian König's avatar Christian König
Browse files

drm/syncobj: make lockdep complain on WAIT_FOR_SUBMIT v3 



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: default avatarChristian König <christian.koenig@amd.com>
Reviewed-by: default avatarDaniel Vetter <daniel.vetter@ffwll.ch>
Acked-by: default avatarPeter Zijlstra (Intel) <peterz@infradead.org>
Link: https://patchwork.freedesktop.org/patch/414944/
parent f987c9e0

drivers/gpu/drm/drm_syncobj.c

+12 −0
Original line number Diff line number Diff line
@@ -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;

include/linux/lockdep.h

+5 −0
Original line number Diff line number Diff line
@@ -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)