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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@vger.kernel.org
Signed-off-by: UCHINO Satoshi <satoshi.uchino@toshiba.co.jp>
Acked-by: Michal Nazarewicz <mina86@mina86.com>
Signed-off-by: Felipe Balbi <balbi@ti.com>
This commit is contained in:
UCHINO Satoshi 2013-05-23 11:10:11 +09:00 committed by Felipe Balbi
parent eb127cb519
commit d68c277b50
1 changed files with 2 additions and 0 deletions
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2
drivers/usb/gadget/f_mass_storage.c
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@ -413,6 +413,7 @@ static int fsg_set_halt(struct fsg_dev *fsg, struct usb_ep *ep)
/* Caller must hold fsg->lock */
static void wakeup_thread(struct fsg_common *common)
{
smp_wmb(); /* ensure the write of bh->state is complete */
/* Tell the main thread that something has happened */
common->thread_wakeup_needed = 1;
if (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(); /* ensure the latest bh->state is visible */
return rc;
}