drm/xe/ufence: Wake up waiters after setting ufence->signalled

[ Upstream commit 37a1cf288e4538eb39b38dbc745fe0da7ae53d94 ]

If a previous ufence is not signalled, vm_bind will return -EBUSY.
Delaying the modification of ufence->signalled can cause issues if the
UMD reuses the same ufence so update ufence->signalled before waking up
waiters.

Cc: Matthew Brost <matthew.brost@intel.com>
Link: https://gitlab.freedesktop.org/drm/xe/kernel/-/issues/3233
Fixes: 977e5b82e090 ("drm/xe: Expose user fence from xe_sync_entry")
Reviewed-by: Matthew Brost <matthew.brost@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20241114150537.4161573-1-nirmoy.das@intel.com
Signed-off-by: Nirmoy Das <nirmoy.das@intel.com>
(cherry picked from commit 553a5d14fcd927194c409b10faced6a6dbc678d1)
Signed-off-by: Thomas Hellström <thomas.hellstrom@linux.intel.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>

diff --git a/drivers/gpu/drm/xe/xe_sync.c b/drivers/gpu/drm/xe/xe_sync.c
index 9d77f2d4096f59e2dd3ebc4ed26685c370ef7a6f..6e17bace67dd13d0d6e10c7c84e037bcfba67511 100644 (file)
--- a/drivers/gpu/drm/xe/xe_sync.c
+++ b/drivers/gpu/drm/xe/xe_sync.c
@@ -85,8 +85,12 @@ static void user_fence_worker(struct work_struct *w)
                mmput(ufence->mm);
        }
 
-       wake_up_all(&ufence->xe->ufence_wq);
+       /*
+        * Wake up waiters only after updating the ufence state, allowing the UMD
+        * to safely reuse the same ufence without encountering -EBUSY errors.
+        */
        WRITE_ONCE(ufence->signalled, 1);
+       wake_up_all(&ufence->xe->ufence_wq);
        user_fence_put(ufence);
 }