vmw_fence_fifo_down() drops fman->lock to wait on a fence and, on
timeout, mutates fman->fence_list via list_del_init() and signals
the fence without re-acquiring the lock. __vmw_fences_update() walks
and removes entries from the same list under fman->lock from any
other waiter, the fence-IRQ thread, or vmw_fences_update(), so the
unlocked list_del_init() can corrupt the list head.
Re-take fman->lock before manipulating fence->head and use
dma_fence_signal_locked(). Wrap the locked signalling in
dma_fence_begin_signalling() / dma_fence_end_signalling() so the
lockdep annotation that dma_fence_signal() previously provided is
preserved (the same pattern as __vmw_fences_update()).
dma_fence_put() is moved outside the lock to avoid a recursive
acquire from vmw_fence_obj_destroy(), which also takes fman->lock.
Fixes: ae2a104058e2 ("vmwgfx: Implement fence objects")
Cc: [email protected]
Assisted-by: Claude:claude-opus-4.7
Signed-off-by: Zack Rusin <[email protected]>
---
drivers/gpu/drm/vmwgfx/vmwgfx_fence.c | 13 ++++++++++++-
1 file changed, 12 insertions(+), 1 deletion(-)
diff --git a/drivers/gpu/drm/vmwgfx/vmwgfx_fence.c
b/drivers/gpu/drm/vmwgfx/vmwgfx_fence.c
index 4ef84ff9b638..384c6736cf6b 100644
--- a/drivers/gpu/drm/vmwgfx/vmwgfx_fence.c
+++ b/drivers/gpu/drm/vmwgfx/vmwgfx_fence.c
@@ -367,13 +367,24 @@ void vmw_fence_fifo_down(struct vmw_fence_manager *fman)
ret = vmw_fence_obj_wait(fence, false, false,
VMW_FENCE_WAIT_TIMEOUT);
+ spin_lock(&fman->lock);
if (unlikely(ret != 0)) {
+ bool cookie = dma_fence_begin_signalling();
+
list_del_init(&fence->head);
- dma_fence_signal(&fence->base);
+ if (fence->waiter_added) {
+ vmw_seqno_waiter_remove(fman->dev_priv);
+ fence->waiter_added = false;
+ }
+ dma_fence_signal_locked(&fence->base);
+ dma_fence_end_signalling(cookie);
}
BUG_ON(!list_empty(&fence->head));
+ spin_unlock(&fman->lock);
+
dma_fence_put(&fence->base);
+
spin_lock(&fman->lock);
}
spin_unlock(&fman->lock);
--
2.51.0
