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drm/nouveau: Simplify nouveau_cli_work

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Lets simplify and make clearer the fence lock cycling workaround in
nouveau_cli_work().

The reason for the workaround is that the worker processes the list of
pending work items (and so fence callbacks) opportunisticaly, while
dma_fence_is_signaled() returns true as soon as a the fence is signaled.
It is therefore not allowed for the opportunistic processing to free the
work item, since the fence callback processing can still be in the process
of dereferencing work->cb.

This wasn't very clear in the code so clarify it with a nice comment.

In the process we replace the somewhat interleaved and not very readable
nouveau_cli_work_ready() helper with a direct dma_fence_is_signaled, which
is even faster since it removes the lock cycling from the unsignaled fence
path.

Signed-off-by: Tvrtko Ursulin <tvrtko.ursulin@igalia.com>
Cc: Philipp Stanner <phasta@kernel.org>
Cc: Lyude Paul <lyude@redhat.com>
Cc: Danilo Krummrich <dakr@kernel.org>
Cc: nouveau@lists.freedesktop.org
Link: https://patch.msgid.link/20260615092607.80917-1-tvrtko.ursulin@igalia.com
Signed-off-by: Danilo Krummrich <dakr@kernel.org>
This commit is contained in:
Tvrtko Ursulin
2026-06-15 10:26:07 +01:00
committed by Danilo Krummrich
parent d008141ed4
commit a80d12eafa
1 changed files with 17 additions and 17 deletions
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34
drivers/gpu/drm/nouveau/nouveau_drm.c
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@@ -153,22 +153,6 @@ nouveau_name(struct drm_device *dev)
return nouveau_platform_name(to_platform_device(dev->dev));
}
static inline bool
nouveau_cli_work_ready(struct dma_fence *fence)
{
unsigned long flags;
bool ret = true;
dma_fence_lock_irqsave(fence, flags);
if (!dma_fence_is_signaled_locked(fence))
ret = false;
dma_fence_unlock_irqrestore(fence, flags);
if (ret == true)
dma_fence_put(fence);
return ret;
}
static void
nouveau_cli_work(struct work_struct *w)
{
@@ -176,9 +160,25 @@ nouveau_cli_work(struct work_struct *w)
struct nouveau_cli_work *work, *wtmp;
mutex_lock(&cli->lock);
list_for_each_entry_safe(work, wtmp, &cli->worker, head) {
if (!work->fence || nouveau_cli_work_ready(work->fence)) {
struct dma_fence *fence = work->fence;
if (!fence || dma_fence_is_signaled(fence)) {
if (fence) {
unsigned long flags;
/*
* Because fence can still be in the process of
* processing the callback list, and the
* callback references the work we are about to
* free, we need to sync with the callback
* processing before freeing the work.
*/
dma_fence_lock_irqsave(fence, flags);
dma_fence_unlock_irqrestore(fence, flags);
}
list_del(&work->head);
work->func(work);
dma_fence_put(fence);
}
}
mutex_unlock(&cli->lock);