Quoting Chris Wilson (2019-10-03 14:19:46)
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").
v2: Refactor all 3 enable_signaling paths to use a common function.
Signed-off-by: Chris Wilson chris@chris-wilson.co.uk
drivers/dma-buf/dma-fence.c | 78 +++++++++++++++++-------------------- 1 file changed, 35 insertions(+), 43 deletions(-)
diff --git a/drivers/dma-buf/dma-fence.c b/drivers/dma-buf/dma-fence.c index 2c136aee3e79..4a1442a93f04 100644 --- a/drivers/dma-buf/dma-fence.c +++ b/drivers/dma-buf/dma-fence.c @@ -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 true;
Perhaps this should be false for "could not _enable_ signaling as it was already signaled", which is closer to the original.
if (!was_set && fence->ops->enable_signaling) {if (!fence->ops->enable_signaling(fence)) {dma_fence_signal_locked(fence);return true;}trace_dma_fence_enable_signal(fence);}return false;+}
/**
- dma_fence_enable_sw_signaling - enable signaling on fence
- @fence: the fence to enable
@@ -285,19 +309,12 @@ 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);spin_lock_irqsave(fence->lock, flags);if (!fence->ops->enable_signaling(fence))dma_fence_signal_locked(fence);
if (test_bit(DMA_FENCE_FLAG_SIGNALED_BIT, &fence->flags))return;
spin_unlock_irqrestore(fence->lock, flags);}
spin_lock_irqsave(fence->lock, flags);__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))
if (__dma_fence_enable_signaling(fence)) {INIT_LIST_HEAD(&cb->node); 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) {
} else { cb->func = func; list_add_tail(&cb->node, &fence->cb_list);
} elseINIT_LIST_HEAD(&cb->node);
}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;-- 2.23.0