[68/88] usb: gadget: f_mass_storage: add missing memory barrier for thread_wakeup_needed

Steven Rostedt
2013-08-13T16:32:03Z

[-- Attachment #1: 0068-usb-gadget-f_mass_storage-add-missing-memory-barrier.patch --]
[-- Type: text/plain, Size: 1685 bytes --]

3.6.11.7-rc1 stable review patch.
If anyone has any objections, please let me know.

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

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

[ Upstream commit d68c277b501889b3a50c179d1c3d704db7947b83 ]

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>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
---
drivers/usb/gadget/f_mass_storage.c | 2 ++
1 file changed, 2 insertions(+)

diff --git a/drivers/usb/gadget/f_mass_storage.c b/drivers/usb/gadget/f_mass_storage.c
index 4f1142e..4d60ad3 100644
--- a/drivers/usb/gadget/f_mass_storage.c
+++ b/drivers/usb/gadget/f_mass_storage.c
@@ -433,6 +433,7 @@ 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)
@@ -652,6 +653,7 @@ 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;
}

--
1.7.10.4