[PATCH] usb: gadget: f_mass_storage: add missing memory barrier for thread_wakeup_needed

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Without this memory barrier, the file-storage thread may fail to
escape from the following while loop, because it may observe new
common->thread_wakeup_needed and old bh->state which are updated by
the callback functions.

	/* Wait for the CBW to arrive */
	while (bh->state != BUF_STATE_FULL) {
		rc = sleep_thread(common);
		if (rc)
			return rc;
	}

Cc: stable@xxxxxxxxxxxxxxx
Signed-off-by: UCHINO Satoshi <satoshi.uchino@xxxxxxxxxxxxx>
---
 drivers/usb/gadget/f_mass_storage.c |    2 ++
 1 files changed, 2 insertions(+), 0 deletions(-)

diff --git a/drivers/usb/gadget/f_mass_storage.c b/drivers/usb/gadget/f_mass_storage.c
index fc5c16c..0b6d351 100644
--- a/drivers/usb/gadget/f_mass_storage.c
+++ b/drivers/usb/gadget/f_mass_storage.c
@@ -414,6 +414,7 @@ static int fsg_set_halt(struct fsg_dev *fsg, struct usb_ep *ep)
 static void wakeup_thread(struct fsg_common *common)
 {
 	/* Tell the main thread that something has happened */
+	smp_wmb();
 	common->thread_wakeup_needed = 1;
 	if (common->thread_task)
 		wake_up_process(common->thread_task);
@@ -632,6 +633,7 @@ static int sleep_thread(struct fsg_common *common)
 	}
 	__set_current_state(TASK_RUNNING);
 	common->thread_wakeup_needed = 0;
+	smp_rmb();
 	return rc;
 }
 
-- 
1.7.4.1


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