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@vmware.com Reviewed-by: Roland Scheidegger sroland@vmware.com Fixes: d1a73c641afd ("drm/vmwgfx: Make sure we unpin no longer needed buffers") Cc: dri-devel@lists.freedesktop.org Signed-off-by: Zack Rusin zackr@vmware.com
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);
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