[PATCH] drm/syncobj: Don't leak fences when WAIT_FOR_SUBMIT is set

[Jason Ekstrand <jason@jlekstrand.net>]

We attempt to get fences earlier in the hopes that everything will
already have fences and no callbacks will be needed.  If we do succeed
in getting a fence, getting one a second time will result in a duplicate
ref with no unref.  This is causing memory leaks in Vulkan applications
that create a lot of fences; playing for a few hours can, apparently,
bring down the system.

Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=107899
Signed-off-by: Jason Ekstrand <jason@jlekstrand.net>
Cc: stable@vger.kernel.org
---
 drivers/gpu/drm/drm_syncobj.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/drivers/gpu/drm/drm_syncobj.c b/drivers/gpu/drm/drm_syncobj.c
index adb3cb27d31e..759278fef35a 100644
--- a/drivers/gpu/drm/drm_syncobj.c
+++ b/drivers/gpu/drm/drm_syncobj.c
@@ -97,6 +97,8 @@ static int drm_syncobj_fence_get_or_add_callback(struct drm_syncobj *syncobj,
 {
 	int ret;
 
+	WARN_ON(*fence);
+
 	*fence = drm_syncobj_fence_get(syncobj);
 	if (*fence)
 		return 1;
@@ -743,6 +745,9 @@ static signed long drm_syncobj_array_wait_timeout(struct drm_syncobj **syncobjs,
 
 	if (flags & DRM_SYNCOBJ_WAIT_FLAGS_WAIT_FOR_SUBMIT) {
 		for (i = 0; i < count; ++i) {
+			if (entries[i].fence)
+				continue;
+
 			drm_syncobj_fence_get_or_add_callback(syncobjs[i],
 							      &entries[i].fence,
 							      &entries[i].syncobj_cb,
-- 
2.17.1