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

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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: Francisco Jerez <currojerez@riseup.net>
Signed-off-by: Ben Skeggs <bskeggs@redhat.com>
This commit is contained in:
Francisco Jerez
2010-10-18 03:56:40 +02:00
committed by Ben Skeggs
parent 2a6789ae5e
commit 2b478addc0
1 changed files with 15 additions and 9 deletions
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24
drivers/gpu/drm/nouveau/nouveau_fence.c
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@@ -128,7 +128,7 @@ nouveau_fence_new(struct nouveau_channel *chan, struct nouveau_fence **pfence,
struct nouveau_channel * struct nouveau_channel *
nouveau_fence_channel(struct nouveau_fence *fence) nouveau_fence_channel(struct nouveau_fence *fence)
{ {
return fence ? fence->channel : NULL; return fence ? nouveau_channel_get_unlocked(fence->channel) : NULL;
} }
int int
@@ -381,17 +381,18 @@ nouveau_fence_sync(struct nouveau_fence *fence,
struct nouveau_channel *chan = nouveau_fence_channel(fence); struct nouveau_channel *chan = nouveau_fence_channel(fence);
struct drm_device *dev = wchan->dev; struct drm_device *dev = wchan->dev;
struct nouveau_semaphore *sema; struct nouveau_semaphore *sema;
int ret; int ret = 0;
if (likely(!fence || chan == wchan || if (likely(!chan || chan == wchan ||
nouveau_fence_signalled(fence, NULL))) nouveau_fence_signalled(fence, NULL)))
return 0; goto out;
sema = alloc_semaphore(dev); sema = alloc_semaphore(dev);
if (!sema) { if (!sema) {
/* Early card or broken userspace, fall back to /* Early card or broken userspace, fall back to
* software sync. */ * 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 /* 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 * order issues
*/ */
if (!mutex_trylock(&chan->mutex)) { if (!mutex_trylock(&chan->mutex)) {
free_semaphore(&sema->ref); ret = nouveau_fence_wait(fence, NULL, true, false);
return nouveau_fence_wait(fence, NULL, true, false); goto out_unref;
} }
/* Make wchan wait until it gets signalled */ /* Make wchan wait until it gets signalled */
ret = emit_semaphore(wchan, NV_SW_SEMAPHORE_ACQUIRE, sema); ret = emit_semaphore(wchan, NV_SW_SEMAPHORE_ACQUIRE, sema);
if (ret) if (ret)
goto out; goto out_unlock;
/* Signal the semaphore from chan */ /* Signal the semaphore from chan */
ret = emit_semaphore(chan, NV_SW_SEMAPHORE_RELEASE, sema); ret = emit_semaphore(chan, NV_SW_SEMAPHORE_RELEASE, sema);
out_unlock:
mutex_unlock(&chan->mutex); mutex_unlock(&chan->mutex);
out: out_unref:
kref_put(&sema->ref, free_semaphore); kref_put(&sema->ref, free_semaphore);
out:
if (chan)
nouveau_channel_put_unlocked(&chan);
return ret; return ret;
} }