On Fri, Mar 15 2013, UCHINO Satoshi <[email protected]> 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]> > --- > 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) ooo +----<email/xmpp: [email protected]>--------------ooO--(_)--Ooo--
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