usb: gadget: f_mass_storage: add missing memory barrier for thread_wakeup_needed

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>

diff --git a/drivers/usb/gadget/f_mass_storage.c b/drivers/usb/gadget/f_mass_storage.c
index 97666e8..c35a9ec 100644 (file)
--- a/drivers/usb/gadget/f_mass_storage.c
+++ b/drivers/usb/gadget/f_mass_storage.c
@@ -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;
 }