Re: [PATCH] clockevents/drivers/cs5535: improve resilience to spurious interrupts

[David Kozub]

On Fri, 20 Oct 2017, Daniel Lezcano wrote:

> On 20/10/2017 00:25, Thomas Gleixner wrote:
> > On Fri, 20 Oct 2017, Daniel Lezcano wrote:
> >
> > > On 19/10/2017 22:57, David Kozub wrote:
> > > > This solves a BUG on ALIX 2c3 where mfgpt_tick is called before
> > > > clockevents_config_and_register returns. This caused mfgpt_tick to call a
> > > > null function pointer.
> > > >
> > > > Thanks to Daniel Lezcano and Thomas Gleixner for helping me analyze this
> > > > and suggesting a solution.
> > > >
> > > > Suggested-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
> > > > Signed-off-by: David Kozub <zub@xxxxxxxxxxxxxxxxxx>
> > > > ---
> > >
> > > Thank for sending this fix.
> > >
> > > Can you check if the commit 8f9327cbb is the one introducing the
> > > regression ? So we can add the proper tags and propagate the fix to stable.
> >
> > No it's not.
> >
> > -       if (cs5535_tick_mode == CLOCK_EVT_MODE_SHUTDOWN)
> > +       if (clockevent_state_shutdown(&cs5535_clockevent))
> >
> > This particular problem of the missing detached state check has been there
> > forever and went unnoticed for whatever reason.
>
> The detached condition was artificially caught by the initialized variable:
>
> -static unsigned int cs5535_tick_mode = CLOCK_EVT_MODE_SHUTDOWN;
>
> The patch 8f9327cbb removes the variable, so very likely this is where
> the problem appeared.

I will try to test that. But I won't have access to the device till Sunday 
evening. I've had big trouble trying to run kernels > 4.1-rc5 on the 
device and if I'm looking correctly the commit was introduced in 4.3-rc1. 
But I'll try to figure something out.

Best regards,
David