Messages in this thread | | | From | Jassi Brar <> | Date | Thu, 15 Oct 2020 13:45:54 -0500 | Subject | Re: [PATCH] mailbox: cancel timer before starting it |
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On Thu, Oct 15, 2020 at 8:58 AM Jerome Brunet <jbrunet@baylibre.com> wrote: > > > On Thu 15 Oct 2020 at 15:46, Ionela Voinescu <ionela.voinescu@arm.com> wrote: > > > Hi guys, > > > > On Wednesday 23 Sep 2020 at 14:39:16 (+0200), Jerome Brunet wrote: > >> If the txdone is done by polling, it is possible for msg_submit() to start > >> the timer while txdone_hrtimer() callback is running. If the timer needs > >> recheduling, it could already be enqueued by the time hrtimer_forward_now() > >> is called, leading hrtimer to loudly complain. > >> > >> WARNING: CPU: 3 PID: 74 at kernel/time/hrtimer.c:932 hrtimer_forward+0xc4/0x110 > >> CPU: 3 PID: 74 Comm: kworker/u8:1 Not tainted 5.9.0-rc2-00236-gd3520067d01c-dirty #5 > >> Hardware name: Libre Computer AML-S805X-AC (DT) > >> Workqueue: events_freezable_power_ thermal_zone_device_check > >> pstate: 20000085 (nzCv daIf -PAN -UAO BTYPE=--) > >> pc : hrtimer_forward+0xc4/0x110 > >> lr : txdone_hrtimer+0xf8/0x118 > >> [...] > >> > >> Canceling the timer before starting it ensure that the timer callback is > >> not running when the timer is started, solving this race condition. > >> > >> Fixes: 0cc67945ea59 ("mailbox: switch to hrtimer for tx_complete polling") > >> Reported-by: Da Xue <da@libre.computer> > >> Signed-off-by: Jerome Brunet <jbrunet@baylibre.com> > >> --- > >> drivers/mailbox/mailbox.c | 8 ++++++-- > >> 1 file changed, 6 insertions(+), 2 deletions(-) > >> > >> diff --git a/drivers/mailbox/mailbox.c b/drivers/mailbox/mailbox.c > >> index 0b821a5b2db8..34f9ab01caef 100644 > >> --- 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 ?
thanks
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