linux-kernel - RE: [PATCH v2 2/4] platform/x86: intel

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Date:   Fri, 24 Nov 2017 02:51:08 +0000
From:   "Chakravarty, Souvik K" <souvik.k.chakravarty@...el.com>
To:     Andy Shevchenko <andy.shevchenko@...il.com>
CC:     Platform Driver <platform-driver-x86@...r.kernel.org>,
        "dvhart@...radead.org" <dvhart@...radead.org>,
        Andy Shevchenko <andy@...radead.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "Bhardwaj, Rajneesh" <rajneesh.bhardwaj@...el.com>
Subject: RE: [PATCH v2 2/4] platform/x86: intel_telemetry: Fix suspend stats

On Fri, November 24, 2017 at 2:55 AM, Andy Shevchenko <andy.shevchenko@...il.com> wrote:
> On Tue, Nov 21, 2017 at 4:36 PM, Souvik Kumar Chakravarty
> <souvik.k.chakravarty@...el.com> wrote:
> > Suspend stats are not reported consistently due to a limitation in the
> > PMC firmware. This limitation causes a delay in updating the s0ix
> > counters and residencies in the telemetry log upon s0ix exit. As a
> > consequence, reading these counters from the suspend-exit notifier may result
> in zero read.
> >
> > This patch fixes this issue by cross-verifying the s0ix residencies
> > from the GCR TELEM registers in case the counters are not incremented
> > in the telemetry log after suspend.
> >
> > This fixes https://bugzilla.kernel.org/show_bug.cgi?id=197833
> >
> > We also remove unnecessary 'static' qualifiers from local variables.
> >
> > Reported-and-tested-by: Rajneesh Bhardwaj
> > <rajneesh.bhardwaj@...el.com>
> > Signed-off-by: Souvik Kumar Chakravarty
> > <souvik.k.chakravarty@...el.com>
> 
> > -       static u32 suspend_shlw_ctr_exit, suspend_deep_ctr_exit;
> > -       static u64 suspend_shlw_res_exit, suspend_deep_res_exit;
> >         struct telemetry_debugfs_conf *conf = debugfs_conf;
> > +       u32 suspend_shlw_ctr_exit, suspend_deep_ctr_exit;
> > +       u64 suspend_shlw_res_exit, suspend_deep_res_exit;
> >         int ret, index;
> 
> > +       if (suspend_shlw_ctr_exit == suspend_shlw_ctr_temp &&
> > +           suspend_deep_ctr_exit == suspend_deep_ctr_temp) {
> 
> kbuildbot is absolutely right. How this code is supposed to work? It's flaky.

suspend_shlw_ctr_exit & suspend_deep_ctr_exit have already been initialized before this comparison (comparing the counters before and after sleep).
I will explicitly initialize them so that kbuildbot does not complain.
> 
> Please, redesign this approach.
> 
> --
> With Best Regards,
> Andy Shevchenko