On Fri, Mar 15 2013, UCHINO Satoshi <satoshi.uchino@xxxxxxxxxxxxx> wrote:
> 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>
> ---
> 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 fc5c16c..0b6d351 100644
> --- a/drivers/usb/gadget/f_mass_storage.c
> +++ b/drivers/usb/gadget/f_mass_storage.c
> @@ -414,6 +414,7 @@ static int fsg_set_halt(struct fsg_dev *fsg, struct usb_ep *ep)
> static void wakeup_thread(struct fsg_common *common)
> {
> /* Tell the main thread that something has happened */
> + smp_wmb();
> common->thread_wakeup_needed = 1;
> if (common->thread_task)
> wake_up_process(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();
> return rc;
> }
In both places, add comment describing why the barrier is needed.
--
Best regards, _ _
.o. | Liege of Serenely Enlightened Majesty of o' \,=./ `o
..o | Computer Science, Michał “mina86” Nazarewicz (o o)
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