Re: [PATCH v2 3/9] clocksource/cadence_ttc: Store timer frequencyin driver data

[Daniel Lezcano]

On 12/19/2013 10:23 PM, SÃren Brinkmann wrote:
> Hi Daniel,
>
> On Thu, Dec 19, 2013 at 09:53:14PM +0100, Daniel Lezcano wrote:
> > On 12/19/2013 07:32 PM, SÃren Brinkmann wrote:
> > > Hi Daniel,
> > >
> > > On Wed, Dec 18, 2013 at 10:58:26PM +0100, Daniel Lezcano wrote:
> > > > On 12/18/2013 05:47 PM, SÃren Brinkmann wrote:
> > > > > Hi Daniel,
> > > > >
> > > > > On Wed, Dec 18, 2013 at 03:53:51PM +0100, Daniel Lezcano wrote:
> > > > > > On 12/17/2013 08:21 PM, SÃren Brinkmann wrote:
> > > > > > > Hi Daniel,
> > > > > > >
> > > > > > > On Tue, Nov 26, 2013 at 05:04:50PM -0800, Soren Brinkmann wrote:
> > > > > > > > It is not allowed to call clk_get_rate() from interrupt context. To
> > > > > > > > avoid such calls the timer input frequency is stored in the driver's
> > > > > > > > data struct which makes it accessible to the driver in any context.
> > > > > > > >
> > > > > > > > Signed-off-by: Soren Brinkmann <soren.brinkmann@xxxxxxxxxx>
> > > > > > > > Acked-by: Daniel Lezcano <daniel.lezcano@xxxxxxxxxx>
> > > > > > >
> > > > > > > I doubt that we'll resolve all issues with this series before the
> > > > > > > holidays or even the next merge window. Could you take this patch into
> > > > > > > your tree for 3.14? It is not directly related to the cpufreq work and
> > > > > > > fixes an actual issue that triggers a kernel WARN under some condition
> > > > > > > (I missed preserving the details and the trace). That would take the
> > > > > > > easy stuff out of the way and we can focus on the more controversial
> > > > > > > changes.
> > > > > >
> > > > > > You are asking to take it for 3.14 but shouldn't it go as a 3.13 fix ?
> > > > >
> > > > > That's also an option. As I remember, the patch fixes a kernel WARN. The
> > > > > system still seemed operational though. Up to you whether this is
> > > > > considered severe enough for the 3.13 series. I'm happy either way.
> > > >
> > > > I was not able to reproduce the WARN with my board.
> > > >
> > > > Please, could you give the WARN or give the procedure to reproduce it ?
> > >
> > > I can't either... I thought I saw the WARN on a vanilla kernel during
> > > boot (IIRC, when cpuidle started). Is there any chance the timer core
> > > calls the timer's set_mode() from interrupt context?
> > > Anyway, let's drop it for now. I'll make sure to record more information
> > > in case it reappears.
> >
> > Finally I was able to reproduce it with the highres timers disabled,
> > the periodic tick system and the locks debug.
> >
> > Indeed, we are in an interrupt context (IPI) and we are calling
> > clk_get_rate in the the set_mode function which in turn ends up by
> > getting a mutex... Even if that does not hang, it is a potential
> > kernel crash so I will apply the patch with an updated changelog.
>
> Thanks! Kind of comforting to know that the issue I tried to fix actually exists.

Applied to my tree as a 3.13 fix.

Thanks !
  -- Daniel



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