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>
Acked-by: Michal Nazarewicz <mina86@xxxxxxxxxx>
---
Resending with revised to and cc list and Acked-by line.
Cf. http://marc.info/?l=linux-usb&m=136361467905630&w=2
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 97666e8..c35a9ec 100644
--- 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;
}
--
1.7.4.1
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