On 03/10/2019 14:09, Chris Wilson wrote:
Quoting Chris Wilson (2019-10-03 10:36:18)
Make dma_fence_enable_sw_signaling() behave like its
dma_fence_add_callback() and dma_fence_default_wait() counterparts and
perform the test to enable signaling under the fence->lock, along with
the action to do so. This ensure that should an implementation be trying
to flush the cb_list (by signaling) on retirement before freeing the
fence, it can do so in a race-free manner.
See also 0fc89b6802ba ("dma-fence: Simply wrap dma_fence_signal_locked
with dma_fence_signal").
Signed-off-by: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx>
---
drivers/dma-buf/dma-fence.c | 11 +++++------
1 file changed, 5 insertions(+), 6 deletions(-)
diff --git a/drivers/dma-buf/dma-fence.c b/drivers/dma-buf/dma-fence.c
index 2c136aee3e79..587727089134 100644
--- a/drivers/dma-buf/dma-fence.c
+++ b/drivers/dma-buf/dma-fence.c
@@ -285,19 +285,18 @@ void dma_fence_enable_sw_signaling(struct dma_fence *fence)
{
unsigned long flags;
+ if (test_bit(DMA_FENCE_FLAG_SIGNALED_BIT, &fence->flags))
+ return;
+
+ spin_lock_irqsave(fence->lock, flags);
if (!test_and_set_bit(DMA_FENCE_FLAG_ENABLE_SIGNAL_BIT,
&fence->flags) &&
- !test_bit(DMA_FENCE_FLAG_SIGNALED_BIT, &fence->flags) &&
Staring at this in discussion with Tvrtko, we can't drop this check
either. After which this looks almost identical with the other
enable_signaling callers.
Ah yes true, DMA_FENCE_FLAG_SIGNALED_BIT has to be reliably checked
before the enable_signalling callback. I retract my previous r-b. :)
Regards,
Tvrtko
fence->ops->enable_signaling) {
trace_dma_fence_enable_signal(fence);
-
- spin_lock_irqsave(fence->lock, flags);
-
if (!fence->ops->enable_signaling(fence))
dma_fence_signal_locked(fence);
-
- spin_unlock_irqrestore(fence->lock, flags);
}
+ spin_unlock_irqrestore(fence->lock, flags);
}
EXPORT_SYMBOL(dma_fence_enable_sw_signaling);
--
2.23.0
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