From c7dacf5b0f32957b24ef29df1207dc2cd8307743 Mon Sep 17 00:00:00 2001 From: Jassi Brar Date: Fri, 16 Oct 2020 12:20:56 -0500 Subject: [PATCH] mailbox: avoid timer start from callback 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 [...] This can be fixed by not starting the timer from the callback path. Which requires the timer reloading as long as any message is queued on the channel, and not just when current tx is not done yet. Fixes: 0cc67945ea59 ("mailbox: switch to hrtimer for tx_complete polling") Reported-by: Da Xue Reviewed-by: Sudeep Holla Tested-by: Sudeep Holla Acked-by: Jerome Brunet Tested-by: Jerome Brunet Signed-off-by: Jassi Brar --- drivers/mailbox/mailbox.c | 12 +++++++----- 1 file changed, 7 insertions(+), 5 deletions(-) diff --git a/drivers/mailbox/mailbox.c b/drivers/mailbox/mailbox.c index 0b821a5b2db8..3e7d4b20ab34 100644 --- a/drivers/mailbox/mailbox.c +++ b/drivers/mailbox/mailbox.c @@ -82,9 +82,12 @@ 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 */ - hrtimer_start(&chan->mbox->poll_hrt, 0, HRTIMER_MODE_REL); + /* kick start the timer immediately to avoid delays */ + if (!err && (chan->txdone_method & TXDONE_BY_POLL)) { + /* but only if not already active */ + if (!hrtimer_active(&chan->mbox->poll_hrt)) + hrtimer_start(&chan->mbox->poll_hrt, 0, HRTIMER_MODE_REL); + } } static void tx_tick(struct mbox_chan *chan, int r) @@ -122,11 +125,10 @@ static enum hrtimer_restart txdone_hrtimer(struct hrtimer *hrtimer) struct mbox_chan *chan = &mbox->chans[i]; if (chan->active_req && chan->cl) { + resched = true; txdone = chan->mbox->ops->last_tx_done(chan); if (txdone) tx_tick(chan, 0); - else - resched = true; } }