| Message ID | 20190915184539.16724-1-chris@chris-wilson.co.uk (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | [1/2] dma-fence: Serialise signal enabling (dma_fence_enable_sw_signaling) | expand |
On 15/09/2019 19:45, Chris Wilson wrote: > 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@chris-wilson.co.uk> > --- > 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, I dare not to ask if this couldn't be the non-atomic version, but I have empirically proven to myself things are not that straightforward around here. > &fence->flags) && > - !test_bit(DMA_FENCE_FLAG_SIGNALED_BIT, &fence->flags) && > 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); > > Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com> Regards, Tvrtko
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) && 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);
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@chris-wilson.co.uk> --- drivers/dma-buf/dma-fence.c | 11 +++++------ 1 file changed, 5 insertions(+), 6 deletions(-)