diff options
| author | Zbigniew Kempczyński <zbigniew.kempczynski@intel.com> | 2025-08-20 10:39:04 +0200 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2025-09-04 16:55:38 +0200 |
| commit | dc023a2821e4137f0fe0d95e49505e11a152b705 (patch) | |
| tree | 01b69957bf28c466f759dc8768c75309758ef0a6 | |
| parent | 630c0e6064daf84f17aad1a7d9ca76b562e3fe47 (diff) | |
drm/xe/xe_sync: avoid race during ufence signaling
[ Upstream commit 04e1f683cd28dc9407b238543871a6e09a570dc0 ]
Marking ufence as signalled after copy_to_user() is too late.
Worker thread which signals ufence by memory write might be raced
with another userspace vm-bind call. In map/unmap scenario unmap
may still see ufence is not signalled causing -EBUSY. Change the
order of marking / write to user-fence fixes this issue.
Fixes: 977e5b82e090 ("drm/xe: Expose user fence from xe_sync_entry")
Link: https://gitlab.freedesktop.org/drm/xe/kernel/-/issues/5536
Signed-off-by: Zbigniew Kempczyński <zbigniew.kempczynski@intel.com>
Cc: Matthew Brost <matthew.brost@intel.com>
Cc: Matthew Auld <matthew.auld@intel.com>
Reviewed-by: Matthew Brost <matthew.brost@intel.com>
Signed-off-by: Matthew Brost <matthew.brost@intel.com>
Link: https://lore.kernel.org/r/20250820083903.2109891-2-zbigniew.kempczynski@intel.com
(cherry picked from commit 8ae04fe9ffc93d6bc3bc63ac08375427d69cee06)
Signed-off-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
| -rw-r--r-- | drivers/gpu/drm/xe/xe_sync.c | 2 |
1 files changed, 1 insertions, 1 deletions
diff --git a/drivers/gpu/drm/xe/xe_sync.c b/drivers/gpu/drm/xe/xe_sync.c index f87276df18f2..82872a51f098 100644 --- a/drivers/gpu/drm/xe/xe_sync.c +++ b/drivers/gpu/drm/xe/xe_sync.c @@ -77,6 +77,7 @@ static void user_fence_worker(struct work_struct *w) { struct xe_user_fence *ufence = container_of(w, struct xe_user_fence, worker); + WRITE_ONCE(ufence->signalled, 1); if (mmget_not_zero(ufence->mm)) { kthread_use_mm(ufence->mm); if (copy_to_user(ufence->addr, &ufence->value, sizeof(ufence->value))) @@ -91,7 +92,6 @@ static void user_fence_worker(struct work_struct *w) * 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); } |