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Subject[14/85] usb: gadget: f_mass_storage: add missing memory barrier for thread_wakeup_needed
3.2.49-rc1 review patch.  If anyone has any objections, please let me know.

------------------

From: UCHINO Satoshi <satoshi.uchino@toshiba.co.jp>

commit d68c277b501889b3a50c179d1c3d704db7947b83 upstream.

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;
}

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>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
---
drivers/usb/gadget/f_mass_storage.c | 2 ++
1 file changed, 2 insertions(+)

--- a/drivers/usb/gadget/f_mass_storage.c
+++ b/drivers/usb/gadget/f_mass_storage.c
@@ -512,6 +512,7 @@ static int fsg_set_halt(struct fsg_dev *
/* 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)
@@ -731,6 +732,7 @@ static int sleep_thread(struct fsg_commo
}
__set_current_state(TASK_RUNNING);
common->thread_wakeup_needed = 0;
+ smp_rmb(); /* ensure the latest bh->state is visible */
return rc;
}



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