On Thu, Oct 15, 2020 at 03:29:35PM +0100, Ionela Voinescu wrote: > Hi Jerome, > > On Thursday 15 Oct 2020 at 15:58:30 (+0200), Jerome Brunet wrote: > > > > On Thu 15 Oct 2020 at 15:46, Ionela Voinescu <ionela.voine...@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 <jbru...@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 ? > > > > I'm not familiar with the mailbox subsystem, so the best I can do right > now is to add Sudeep to Cc, in case this conflicts in some way with the > ARM MHU patches [1]. >
Not it can't be doorbell driver as we use SCPI(old firmware) with upstream MHU driver as is limiting the number of channels to be used. > In the meantime I'll get some traces and get more familiar with the > code. > I will try that too. -- Regards, Sudeep