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sync: protect unlocked access to fence status

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Fence status is checked outside of locks in both sync_fence_wait and
sync_fence_poll.  This patch adds propper barrier protection in these
cases to avoid seeing stale status.

Change-Id: I9d8b6ce6accb415e797df58068a1ccd54e6be445
Signed-off-by: Erik Gilling <konkers@android.com>
This commit is contained in:
Erik Gilling
2012-10-11 12:35:22 -07:00
committed by Iliyan Malchev
parent 8e50d1bf8e
commit c5949fef4b
1 changed files with 17 additions and 1 deletions
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18
drivers/base/sync.c
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@@ -557,6 +557,16 @@ int sync_fence_cancel_async(struct sync_fence *fence,
}
EXPORT_SYMBOL(sync_fence_cancel_async);
static bool sync_fence_check(struct sync_fence *fence)
{
/*
* Make sure that reads to fence->status are ordered with the
* wait queue event triggering
*/
smp_rmb();
return fence->status != 0;
}
int sync_fence_wait(struct sync_fence *fence, long timeout)
{
int err = 0;
@@ -564,7 +574,7 @@ int sync_fence_wait(struct sync_fence *fence, long timeout)
if (timeout > 0) {
timeout = msecs_to_jiffies(timeout);
err = wait_event_interruptible_timeout(fence->wq,
fence->status != 0,
sync_fence_check(fence),
timeout);
} else if (timeout < 0) {
err = wait_event_interruptible(fence->wq, fence->status != 0);
@@ -628,6 +638,12 @@ static unsigned int sync_fence_poll(struct file *file, poll_table *wait)
poll_wait(file, &fence->wq, wait);
/*
* Make sure that reads to fence->status are ordered with the
* wait queue event triggering
*/
smp_rmb();
if (fence->status == 1)
return POLLIN;
else if (fence->status < 0)