On Fri, Oct 16, 2020 at 12:32 PM Ionela Voinescu <ionela.voine...@arm.com> wrote: > > On Thursday 15 Oct 2020 at 13:45:54 (-0500), Jassi Brar wrote: > [..] > > > >> --- a/drivers/mailbox/mailbox.c > > > >> +++ b/drivers/mailbox/mailbox.c > > > >> @@ -82,9 +82,13 @@ static void msg_submit(struct mbox_chan *chan) > > > >> exit: > > > >> spin_unlock_irqrestore(&chan->lock, flags); > > > >> > > > >> - if (!err && (chan->txdone_method & TXDONE_BY_POLL)) > > > >> - /* kick start the timer immediately to avoid delays */ > > > >> + if (!err && (chan->txdone_method & TXDONE_BY_POLL)) { > > > >> + /* Disable the timer if already active ... */ > > > >> + hrtimer_cancel(&chan->mbox->poll_hrt); > > > >> + > > > >> + /* ... and kick start it immediately to avoid delays */ > > > >> hrtimer_start(&chan->mbox->poll_hrt, 0, HRTIMER_MODE_REL); > > > >> + } > > > >> } > > > >> > > > >> static void tx_tick(struct mbox_chan *chan, int r) > > > > > > > > I've tracked a regression back to this commit. Details to reproduce: > > > > > > Hi Ionela, > > > > > > I don't have access to your platform and I don't get what is going on > > > from the log below. > > > > > > Could you please give us a bit more details about what is going on ? > > > > > > All this patch does is add hrtimer_cancel(). > > > * It is needed if the timer had already been started, which is > > > appropriate AFAIU > > > * It is a NO-OP is the timer is not active. > > > > > Can you please try using hrtimer_try_to_cancel() instead ? > > > > Yes, using hrtimer_try_to_cancel() instead works for me. But doesn't > this limit how effective this change is? AFAIU, this will possibly only > reduce the chances for the race condition, but not solve it. >
Indeed, I tried the same and got a lot of -ETIME failures. hrtimer_cancel uses hrtimer_try_to_cancel in loop until it succeeds so that the following hrtimer_start can be done w/o any pending timers. -- Regards, Sudeep