Commit 9c98f021 authored by Chris Wilson's avatar Chris Wilson
Browse files

dma-fence: Serialise signal enabling (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 0fc89b68 ("dma-fence: Simply wrap dma_fence_signal_locked
with dma_fence_signal").

v2: Refactor all 3 enable_signaling paths to use a common function.
v3: Don't argue, just keep the tracepoint in the existing spot.

Signed-off-by: default avatarChris Wilson <chris@chris-wilson.co.uk>
Cc: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Reviewed-by: default avatarTvrtko Ursulin <tvrtko.ursulin@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20191004101140.32713-1-chris@chris-wilson.co.uk
parent bebf0051

drivers/dma-buf/dma-fence.c

+35 −43
Original line number Diff line number Diff line
@@ -273,6 +273,30 @@ void dma_fence_free(struct dma_fence *fence) 
}

EXPORT_SYMBOL(dma_fence_free);



static bool __dma_fence_enable_signaling(struct dma_fence *fence)

{

	bool was_set;



	lockdep_assert_held(fence->lock);



	was_set = test_and_set_bit(DMA_FENCE_FLAG_ENABLE_SIGNAL_BIT,

				   &fence->flags);



	if (test_bit(DMA_FENCE_FLAG_SIGNALED_BIT, &fence->flags))

		return false;



	if (!was_set && fence->ops->enable_signaling) {

		trace_dma_fence_enable_signal(fence);



		if (!fence->ops->enable_signaling(fence)) {

			dma_fence_signal_locked(fence);

			return false;

		}

	}



	return true;

}



/**

 * dma_fence_enable_sw_signaling - enable signaling on fence

 * @fence: the fence to enable
@@ -285,20 +309,13 @@ void dma_fence_enable_sw_signaling(struct dma_fence *fence) 
{

	unsigned long 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);

	if (test_bit(DMA_FENCE_FLAG_SIGNALED_BIT, &fence->flags))

		return;



	spin_lock_irqsave(fence->lock, flags);



		if (!fence->ops->enable_signaling(fence))

			dma_fence_signal_locked(fence);



	__dma_fence_enable_signaling(fence);

	spin_unlock_irqrestore(fence->lock, flags);

}

}

EXPORT_SYMBOL(dma_fence_enable_sw_signaling);



/**
@@ -331,7 +348,6 @@ int dma_fence_add_callback(struct dma_fence *fence, struct dma_fence_cb *cb, 
{

	unsigned long flags;

	int ret = 0;

	bool was_set;



	if (WARN_ON(!fence || !func))

		return -EINVAL;
@@ -343,25 +359,14 @@ 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);



	if (test_bit(DMA_FENCE_FLAG_SIGNALED_BIT, &fence->flags))

		ret = -ENOENT;

	else if (!was_set && fence->ops->enable_signaling) {

		trace_dma_fence_enable_signal(fence);



		if (!fence->ops->enable_signaling(fence)) {

			dma_fence_signal_locked(fence);

			ret = -ENOENT;

		}

	}



	if (!ret) {

	if (__dma_fence_enable_signaling(fence)) {

		cb->func = func;

		list_add_tail(&cb->node, &fence->cb_list);

	} else

	} else {

		INIT_LIST_HEAD(&cb->node);

		ret = -ENOENT;

	}



	spin_unlock_irqrestore(fence->lock, flags);



	return ret;
@@ -461,7 +466,6 @@ dma_fence_default_wait(struct dma_fence *fence, bool intr, signed long timeout) 
	struct default_wait_cb cb;

	unsigned long flags;

	signed long ret = timeout ? timeout : 1;

	bool was_set;



	if (test_bit(DMA_FENCE_FLAG_SIGNALED_BIT, &fence->flags))

		return ret;
@@ -473,21 +477,9 @@ 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);



	if (test_bit(DMA_FENCE_FLAG_SIGNALED_BIT, &fence->flags))

	if (!__dma_fence_enable_signaling(fence))

		goto out;



	if (!was_set && fence->ops->enable_signaling) {

		trace_dma_fence_enable_signal(fence);



		if (!fence->ops->enable_signaling(fence)) {

			dma_fence_signal_locked(fence);

			goto out;

		}

	}



	if (!timeout) {

		ret = 0;

		goto out;

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