Commit 2b478add authored by Francisco Jerez's avatar Francisco Jerez Committed by Ben Skeggs

drm/nouveau: Avoid race in the interchannel sync code.

It needs a "strong" channel reference because it actually writes to
the channel pushbuf, otherwise the corresponding FIFO context could
get kicked off in the middle of nouveau_fence_sync().
Signed-off-by: default avatarFrancisco Jerez <currojerez@riseup.net>
Signed-off-by: default avatarBen Skeggs <bskeggs@redhat.com>
parent 2a6789ae
......@@ -128,7 +128,7 @@ nouveau_fence_new(struct nouveau_channel *chan, struct nouveau_fence **pfence,
struct nouveau_channel *
nouveau_fence_channel(struct nouveau_fence *fence)
{
return fence ? fence->channel : NULL;
return fence ? nouveau_channel_get_unlocked(fence->channel) : NULL;
}
int
......@@ -381,17 +381,18 @@ nouveau_fence_sync(struct nouveau_fence *fence,
struct nouveau_channel *chan = nouveau_fence_channel(fence);
struct drm_device *dev = wchan->dev;
struct nouveau_semaphore *sema;
int ret;
int ret = 0;
if (likely(!fence || chan == wchan ||
if (likely(!chan || chan == wchan ||
nouveau_fence_signalled(fence, NULL)))
return 0;
goto out;
sema = alloc_semaphore(dev);
if (!sema) {
/* Early card or broken userspace, fall back to
* software sync. */
return nouveau_fence_wait(fence, NULL, true, false);
ret = nouveau_fence_wait(fence, NULL, true, false);
goto out;
}
/* try to take chan's mutex, if we can't take it right away
......@@ -399,20 +400,25 @@ nouveau_fence_sync(struct nouveau_fence *fence,
* order issues
*/
if (!mutex_trylock(&chan->mutex)) {
free_semaphore(&sema->ref);
return nouveau_fence_wait(fence, NULL, true, false);
ret = nouveau_fence_wait(fence, NULL, true, false);
goto out_unref;
}
/* Make wchan wait until it gets signalled */
ret = emit_semaphore(wchan, NV_SW_SEMAPHORE_ACQUIRE, sema);
if (ret)
goto out;
goto out_unlock;
/* Signal the semaphore from chan */
ret = emit_semaphore(chan, NV_SW_SEMAPHORE_RELEASE, sema);
out_unlock:
mutex_unlock(&chan->mutex);
out:
out_unref:
kref_put(&sema->ref, free_semaphore);
out:
if (chan)
nouveau_channel_put_unlocked(&chan);
return ret;
}
......
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