drm/ttm: Don't deadlock on recursive multi-bo reservations
Add an aid for the driver to detect deadlocks on multi-bo reservations
Update documentation.
Signed-off-by: Thomas Hellstrom <thellstrom@vmware.com>
Reviewed-by: Jerome Glisse <j.glisse@gmail.com>
Signed-off-by: Dave Airlie <airlied@redhat.com>
diff --git a/drivers/gpu/drm/ttm/ttm_bo.c b/drivers/gpu/drm/ttm/ttm_bo.c
index 9ef893d..5d87508 100644
--- a/drivers/gpu/drm/ttm/ttm_bo.c
+++ b/drivers/gpu/drm/ttm/ttm_bo.c
@@ -223,9 +223,18 @@
/**
* Deadlock avoidance for multi-bo reserving.
*/
- if (use_sequence && bo->seq_valid &&
- (sequence - bo->val_seq < (1 << 31))) {
- return -EAGAIN;
+ if (use_sequence && bo->seq_valid) {
+ /**
+ * We've already reserved this one.
+ */
+ if (unlikely(sequence == bo->val_seq))
+ return -EDEADLK;
+ /**
+ * Already reserved by a thread that will not back
+ * off for us. We need to back off.
+ */
+ if (unlikely(sequence - bo->val_seq < (1 << 31)))
+ return -EAGAIN;
}
if (no_wait)