Hi, Zack,
On 4/8/21 7:22 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 | 17 ++++++++++++++++- drivers/gpu/drm/vmwgfx/vmwgfx_mob.c | 8 ++++---- 2 files changed, 20 insertions(+), 5 deletions(-)
diff --git a/drivers/gpu/drm/vmwgfx/vmwgfx_drv.h b/drivers/gpu/drm/vmwgfx/vmwgfx_drv.h index 8087a9013455..03bef9c17e56 100644 --- a/drivers/gpu/drm/vmwgfx/vmwgfx_drv.h +++ b/drivers/gpu/drm/vmwgfx/vmwgfx_drv.h @@ -1517,6 +1517,21 @@ static inline struct vmw_surface *vmw_surface_reference(struct vmw_surface *srf) return srf; }
+/*
- vmw_bo_unpin_safe - currently pinning requires a reservation to be held
- but sometimes it's hard to tell if we're in a callback whose parent
- is already holding a reservation, to avoid deadloacks we have to try
- to get a reservation explicitly to also try to avoid messing up the
- internal ttm lru bo list
- */
+static inline void vmw_bo_unpin_safe(struct ttm_buffer_object *bo) +{
- bool locked = dma_resv_trylock(bo->base.resv);
Isn't there a chance another thread is holding the lock and releasing it at this position?
- ttm_bo_unpin(bo);
- if (locked)
dma_resv_unlock(bo->base.resv);+}
- static inline void vmw_bo_unreference(struct vmw_buffer_object **buf) { struct vmw_buffer_object *tmp_buf = *buf;
@@ -1524,7 +1539,7 @@ static inline void vmw_bo_unreference(struct vmw_buffer_object **buf) *buf = NULL; if (tmp_buf != NULL) { if (tmp_buf->base.pin_count > 0)
ttm_bo_unpin(&tmp_buf->base);
vmw_bo_unpin_safe(&tmp_buf->base);
Hmm. If execbuf is referencing a buffer that someone else has pinned, wouldn't execbuf incorrectly unpin that buffer when calling unreference? Would it perhaps be possible to if needed, use the TTM release_notify callback to unpin any leaking pins similar to what's done in ttm_bo_release? Although that I guess goes somewhat against that recently added WARN_ON_ONCE.
ttm_bo_put(&tmp_buf->base);} } diff --git a/drivers/gpu/drm/vmwgfx/vmwgfx_mob.c b/drivers/gpu/drm/vmwgfx/vmwgfx_mob.c index a0b53141dded..23ffeb2dd6e0 100644 --- a/drivers/gpu/drm/vmwgfx/vmwgfx_mob.c +++ b/drivers/gpu/drm/vmwgfx/vmwgfx_mob.c @@ -277,7 +277,7 @@ static int vmw_otable_batch_setup(struct vmw_private *dev_priv, &batch->otables[i]); }
- ttm_bo_unpin(batch->otable_bo);
- vmw_bo_unpin_safe(batch->otable_bo);
Could it be we're the only user here? If so safe to reserve and unpin.
ttm_bo_put(batch->otable_bo); batch->otable_bo = NULL; return ret; @@ -343,7 +343,7 @@ static void vmw_otable_batch_takedown(struct vmw_private *dev_priv, vmw_bo_fence_single(bo, NULL); ttm_bo_unreserve(bo);
- ttm_bo_unpin(batch->otable_bo);
- vmw_bo_unpin_safe(batch->otable_bo);
Would it be possible to just move ttm_bo_unpin() above the ttm_bo_unreserve() above?
ttm_bo_put(batch->otable_bo); batch->otable_bo = NULL; } @@ -530,7 +530,7 @@ static void vmw_mob_pt_setup(struct vmw_mob *mob, void vmw_mob_destroy(struct vmw_mob *mob) { if (mob->pt_bo) {
ttm_bo_unpin(mob->pt_bo);
vmw_bo_unpin_safe(mob->pt_bo);@@ -646,7 +646,7 @@ int vmw_mob_bind(struct vmw_private *dev_priv, out_no_cmd_space: vmw_fifo_resource_dec(dev_priv); if (pt_set_up) {
ttm_bo_unpin(mob->pt_bo);
vmw_bo_unpin_safe(mob->pt_bo);
Perhaps the same here?
ttm_bo_put(mob->pt_bo); mob->pt_bo = NULL;}
/Thomas