Hi, Zack,
On 4/10/21 8:59 PM, Zack Rusin wrote:
Quite often it's a little hard to tell if reservations are already held
in code paths that unpin bo's. While our pinning/unpinning code should
be more explicit that requires a substential amount of work so instead
we can avoid the issues by making sure we try to reserve before unpinning.
Because we unpin those bo's only on destruction/error paths just that check
tells us if we're already reserved or not and allows to cleanly unpin.
Reviewed-by: Martin Krastev <krastevm@xxxxxxxxxx>
Reviewed-by: Roland Scheidegger <sroland@xxxxxxxxxx>
Fixes: d1a73c641afd ("drm/vmwgfx: Make sure we unpin no longer needed buffers")
Cc: dri-devel@xxxxxxxxxxxxxxxxxxxxx
Signed-off-by: Zack Rusin <zackr@xxxxxxxxxx>
---
drivers/gpu/drm/vmwgfx/vmwgfx_drv.h | 11 +++++++++++
drivers/gpu/drm/vmwgfx/vmwgfx_mob.c | 18 ++++++++++++++----
2 files changed, 25 insertions(+), 4 deletions(-)
diff --git a/drivers/gpu/drm/vmwgfx/vmwgfx_drv.h b/drivers/gpu/drm/vmwgfx/vmwgfx_drv.h
index 8087a9013455..9a3133cb5cc1 100644
--- a/drivers/gpu/drm/vmwgfx/vmwgfx_drv.h
+++ b/drivers/gpu/drm/vmwgfx/vmwgfx_drv.h
@@ -1523,8 +1523,19 @@ static inline void vmw_bo_unreference(struct vmw_buffer_object **buf)
*buf = NULL;
if (tmp_buf != NULL) {
+ /*
+ * currently pinning requires a reservation to be held
+ * but unreference can be called either reserved or not.
+ * To avoid deadloacks we have to try to get a reservation.
+ * This is exlusively to satisfy the requirements of the
+ * unpin, ttm_bo_put will handle delayed deletion for us
+ * in case the bo is really busy.
+ */
+ bool locked = dma_resv_trylock(tmp_buf->base.base.resv);
if (tmp_buf->base.pin_count > 0)
Hmm, Similar to the previous version, I figure someone another thread
might be holding the lock and drop it here?
ttm_bo_unpin(&tmp_buf->base);
And also, if this is a nested reference of a pinned buffer, you'd be
incorrectly unpinning it.
/Thomas
_______________________________________________
dri-devel mailing list
dri-devel@xxxxxxxxxxxxxxxxxxxxx
https://lists.freedesktop.org/mailman/listinfo/dri-devel
