From e3ab954943623e9b2b15ccd157748c92ab629717 Mon Sep 17 00:00:00 2001 From: Erik Gilling Date: Thu, 11 Oct 2012 12:35:22 -0700 Subject: [PATCH] sync: protect unlocked access to fence status 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 --- drivers/base/sync.c | 18 +++++++++++++++++- 1 file changed, 17 insertions(+), 1 deletion(-) diff --git a/drivers/base/sync.c b/drivers/base/sync.c index 82c317ab28a3..f05b708b6c85 100644 --- a/drivers/base/sync.c +++ b/drivers/base/sync.c @@ -555,6 +555,16 @@ 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; @@ -562,7 +572,7 @@ 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); @@ -629,6 +639,12 @@ 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) -- 2.34.1