Re: [PATCH] dma-fence: Use non-atomic bitops while under the lock

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On 03/10/2019 11:12, Tvrtko Ursulin wrote:
From: Tvrtko Ursulin <tvrtko.ursulin@xxxxxxxxx>

We do not have to use atomic bitops when already under the spinlock.

Saves on a handful of lock instruction prefixes, on x86 at least.

Signed-off-by: Tvrtko Ursulin <tvrtko.ursulin@xxxxxxxxx>
Cc: dri-devel@xxxxxxxxxxxxxxxxxxxxx
Cc: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx>
---
  drivers/dma-buf/dma-fence.c | 14 +++++++-------
  1 file changed, 7 insertions(+), 7 deletions(-)

diff --git a/drivers/dma-buf/dma-fence.c b/drivers/dma-buf/dma-fence.c
index 2c136aee3e79..f0b480042e2f 100644
--- a/drivers/dma-buf/dma-fence.c
+++ b/drivers/dma-buf/dma-fence.c
@@ -133,15 +133,15 @@ int dma_fence_signal_locked(struct dma_fence *fence)
lockdep_assert_held(fence->lock); - if (unlikely(test_and_set_bit(DMA_FENCE_FLAG_SIGNALED_BIT,
-				      &fence->flags)))
+	if (unlikely(__test_and_set_bit(DMA_FENCE_FLAG_SIGNALED_BIT,
+					&fence->flags)))

This breaks left right and center so I guess it is more subtle than this!

Regards,

Tvrtko

  		return -EINVAL;
/* Stash the cb_list before replacing it with the timestamp */
  	list_replace(&fence->cb_list, &cb_list);
fence->timestamp = ktime_get();
-	set_bit(DMA_FENCE_FLAG_TIMESTAMP_BIT, &fence->flags);
+	__set_bit(DMA_FENCE_FLAG_TIMESTAMP_BIT, &fence->flags);
  	trace_dma_fence_signaled(fence);
list_for_each_entry_safe(cur, tmp, &cb_list, node) {
@@ -343,8 +343,8 @@ int dma_fence_add_callback(struct dma_fence *fence, struct dma_fence_cb *cb,
spin_lock_irqsave(fence->lock, flags); - was_set = test_and_set_bit(DMA_FENCE_FLAG_ENABLE_SIGNAL_BIT,
-				   &fence->flags);
+	was_set = __test_and_set_bit(DMA_FENCE_FLAG_ENABLE_SIGNAL_BIT,
+				     &fence->flags);
if (test_bit(DMA_FENCE_FLAG_SIGNALED_BIT, &fence->flags))
  		ret = -ENOENT;
@@ -473,8 +473,8 @@ dma_fence_default_wait(struct dma_fence *fence, bool intr, signed long timeout)
  		goto out;
  	}
- was_set = test_and_set_bit(DMA_FENCE_FLAG_ENABLE_SIGNAL_BIT,
-				   &fence->flags);
+	was_set = __test_and_set_bit(DMA_FENCE_FLAG_ENABLE_SIGNAL_BIT,
+				     &fence->flags);
if (test_bit(DMA_FENCE_FLAG_SIGNALED_BIT, &fence->flags))
  		goto out;

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