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dma-buf: fix dma_fence_array_signaled v4

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The function silently assumed that signaling was already enabled for the
dma_fence_array. This meant that without enabling signaling first we would
never see forward progress.

Fix that by falling back to testing each individual fence when signaling
isn't enabled yet.

v2: add the comment suggested by Boris why this is done this way
v3: fix the underflow pointed out by Tvrtko
v4: atomic_read_acquire() as suggested by Tvrtko

Signed-off-by: Christian König <christian.koenig@amd.com>
Reviewed-by: Boris Brezillon <boris.brezillon@collabora.com>
Tested-by: Chia-I Wu <olvaffe@gmail.com>
Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin@igalia.com>
Closes: https://gitlab.freedesktop.org/mesa/mesa/-/issues/12094
Cc: <stable@vger.kernel.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20241112121925.18464-1-christian.koenig@amd.com
This commit is contained in:
Christian König 2024-11-08 09:29:48 +01:00
parent fe52c64943
commit 78ac1c3558
1 changed files with 27 additions and 1 deletions
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28
drivers/dma-buf/dma-fence-array.c
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@ -103,10 +103,36 @@ static bool dma_fence_array_enable_signaling(struct dma_fence *fence)
static bool dma_fence_array_signaled(struct dma_fence *fence)
{
struct dma_fence_array *array = to_dma_fence_array(fence);
int num_pending;
unsigned int i;
if (atomic_read(&array->num_pending) > 0)
/*
* We need to read num_pending before checking the enable_signal bit
* to avoid racing with the enable_signaling() implementation, which
* might decrement the counter, and cause a partial check.
* atomic_read_acquire() pairs with atomic_dec_and_test() in
* dma_fence_array_enable_signaling()
*
* The !--num_pending check is here to account for the any_signaled case
* if we race with enable_signaling(), that means the !num_pending check
* in the is_signalling_enabled branch might be outdated (num_pending
* might have been decremented), but that's fine. The user will get the
* right value when testing again later.
*/
num_pending = atomic_read_acquire(&array->num_pending);
if (test_bit(DMA_FENCE_FLAG_ENABLE_SIGNAL_BIT, &array->base.flags)) {
if (num_pending <= 0)
goto signal;
return false;
}
for (i = 0; i < array->num_fences; ++i) {
if (dma_fence_is_signaled(array->fences[i]) && !--num_pending)
goto signal;
}
return false;
signal:
dma_fence_array_clear_pending_error(array);
return true;
}