| Message ID | 20210410185956.720612-1-zackr@vmware.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | [v2] drm/vmwgfx: Make sure unpinning handles reservations | expand |
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); > 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
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) ttm_bo_unpin(&tmp_buf->base); + if (locked) + dma_resv_unlock(tmp_buf->base.base.resv); 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..f2d625415458 100644 --- a/drivers/gpu/drm/vmwgfx/vmwgfx_mob.c +++ b/drivers/gpu/drm/vmwgfx/vmwgfx_mob.c @@ -94,6 +94,16 @@ static void vmw_mob_pt_setup(struct vmw_mob *mob, struct vmw_piter data_iter, unsigned long num_data_pages); + +static inline void vmw_bo_unpin_unlocked(struct ttm_buffer_object *bo) +{ + int ret = ttm_bo_reserve(bo, false, true, NULL); + BUG_ON(ret != 0); + ttm_bo_unpin(bo); + ttm_bo_unreserve(bo); +} + + /* * vmw_setup_otable_base - Issue an object table base setup command to * the device @@ -277,7 +287,7 @@ static int vmw_otable_batch_setup(struct vmw_private *dev_priv, &batch->otables[i]); } - ttm_bo_unpin(batch->otable_bo); + vmw_bo_unpin_unlocked(batch->otable_bo); ttm_bo_put(batch->otable_bo); batch->otable_bo = NULL; return ret; @@ -341,9 +351,9 @@ static void vmw_otable_batch_takedown(struct vmw_private *dev_priv, BUG_ON(ret != 0); vmw_bo_fence_single(bo, NULL); + ttm_bo_unpin(bo); ttm_bo_unreserve(bo); - ttm_bo_unpin(batch->otable_bo); ttm_bo_put(batch->otable_bo); batch->otable_bo = NULL; } @@ -530,7 +540,7 @@ 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_unlocked(mob->pt_bo); ttm_bo_put(mob->pt_bo); mob->pt_bo = NULL; } @@ -646,7 +656,7 @@ 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_unlocked(mob->pt_bo); ttm_bo_put(mob->pt_bo); mob->pt_bo = NULL; }