On 03/10/2019 22:00, 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").
v2: Refactor all 3 enable_signaling paths to use a common function.
Signed-off-by: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx>
---
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..b58528c1cc9d 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 false;
+
+ if (!was_set && fence->ops->enable_signaling) {
+ if (!fence->ops->enable_signaling(fence)) {
+ dma_fence_signal_locked(fence);
+ return false;
+ }
+
+ trace_dma_fence_enable_signal(fence);
Tracepoint used to come before the enable_signaling call so probably
best to keep it like that.
+ }
+
+ return true;
+}
+
/**
* 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))
- 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;
The rest looks correct to me.
Regards,
Tvrtko
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