On Sat, 3 Sep 2016, Felipe Balbi wrote:
> Hi,
>
> Alan Stern <stern@xxxxxxxxxxxxxxxxxxx> writes:
> > On Fri, 2 Sep 2016, Felipe Balbi wrote:
> >
> >>
> >> Hi,
> >>
> >> Alan Stern <stern@xxxxxxxxxxxxxxxxxxx> writes:
> >>
> >> [...]
> >>
> >> > No, that would be too late. The barrier needs to go between the write
> >> > to common->thead_wakeup_needed and the call to wake_up_process().
> >>
> >> alright, I tested this but it doesn't work. It still hangs :-(
> >
> > Okay, I was wrong. But see my recent reply to Paul; maybe the
> > smp_wmb() in wakeup_thread() needs to be smp_mb().
>
> okay, this seems to be working so far:
>
> modified drivers/usb/gadget/function/f_mass_storage.c
> @@ -395,7 +395,7 @@ 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 */
> + smp_mb(); /* 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)
> @@ -626,7 +626,7 @@ static int sleep_thread(struct fsg_common *common, bool can_freeze)
> }
> __set_current_state(TASK_RUNNING);
> common->thread_wakeup_needed = 0;
> - smp_rmb(); /* ensure the latest bh->state is visible */
> + smp_mb(); /* ensure the latest bh->state is visible */
> return rc;
> }
>
> I'll keep it running over the weekend.
Can you also check the question I mentioned earlier? That is, if you
revert to the original code then when the thread hangs, what does the
call to received_cbw() in get_next_command() return? Or does that
routine not get called at all because the preceding sleep_thread() is
the one that doesn't return?
Alan Stern
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