On Fri, Oct 16, 2020 at 1:38 PM Jerome Brunet <[email protected]> wrote:
>
>
> On Fri 16 Oct 2020 at 19:30, [email protected] wrote:
>
> > From: Jassi Brar <[email protected]>
> >
> > 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.
> >
> > Signed-off-by: Jassi Brar <[email protected]>
> > ---
> > 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..a093a6ecaa66 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 */
>
> It would solve the problem I reported as well but instead of running the
> check immediately (timer with value 0), we will have to wait for the
> next of the timer, it is already started. IOW, there might be a delay
> now. I don't know if this important for the mailbox - the existing
> comments in the code suggested it was.
>
That comment is for when the first message is queued on the channel,
which remains unimpacted.
So, do I have your tested/acked by ?
thnx,
On Fri 16 Oct 2020 at 20:45, Jassi Brar <[email protected]> wrote:
> On Fri, Oct 16, 2020 at 1:38 PM Jerome Brunet <[email protected]> wrote:
>>
>>
>> On Fri 16 Oct 2020 at 19:30, [email protected] wrote:
>>
>> > From: Jassi Brar <[email protected]>
>> >
>> > 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.
>> >
>> > Signed-off-by: Jassi Brar <[email protected]>
>> > ---
>> > 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..a093a6ecaa66 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 */
>>
>> It would solve the problem I reported as well but instead of running the
>> check immediately (timer with value 0), we will have to wait for the
>> next of the timer, it is already started. IOW, there might be a delay
>> now. I don't know if this important for the mailbox - the existing
>> comments in the code suggested it was.
>>
> That comment is for when the first message is queued on the channel,
> which remains unimpacted.
> So, do I have your tested/acked by ?
Sure go ahead
Acked-by: Jerome Brunet <[email protected]>
Tested-by: Jerome Brunet <[email protected]>
>
> thnx,