On Mon, Mar 18 2013, UCHINO Satoshi 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: [email protected]
> Signed-off-by: UCHINO Satoshi <[email protected]>Acked-by: Michal Nazarewicz <[email protected]> > --- > Changes in v2: > - add comments why the barrier is needed > > 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 > -- Best regards, _ _ .o. | Liege of Serenely Enlightened Majesty of o' \,=./ `o ..o | Computer Science, Michał “mina86” Nazarewicz (o o) ooo +----<email/xmpp: [email protected]>--------------ooO--(_)--Ooo--
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