From: "Rafael J. Wysocki" <rafael@kernel.org>
To: Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com>
Cc: "Rafael J. Wysocki" <rafael@kernel.org>,
Jens Axboe <axboe@kernel.dk>,
"Rafael J. Wysocki" <rjw@rjwysocki.net>,
Len Brown <lenb@kernel.org>,
Viresh Kumar <viresh.kumar@linaro.org>,
Linux PM <linux-pm@vger.kernel.org>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH] cpufreq: intel_pstate: Fix for HWP interrupt before driver is ready
Date: Tue, 7 Sep 2021 15:41:23 +0200 [thread overview]
Message-ID: <CAJZ5v0hLXuF8HXcW61TqiBxYnskkb-nkah=XzX2SH8EKGJB-RA@mail.gmail.com> (raw)
In-Reply-To: <980bc41a8bedbd81c199a78ce9f2ab2ef7b9341f.camel@linux.intel.com>
On Mon, Sep 6, 2021 at 9:57 PM Srinivas Pandruvada
<srinivas.pandruvada@linux.intel.com> wrote:
>
> On Mon, 2021-09-06 at 20:25 +0200, Rafael J. Wysocki wrote:
> > On Mon, Sep 6, 2021 at 8:14 PM Srinivas Pandruvada
> > <srinivas.pandruvada@linux.intel.com> wrote:
> > >
> > > On Mon, 2021-09-06 at 19:54 +0200, Rafael J. Wysocki wrote:
> > > >
> [...]
>
> > > >
> > > We are handling offline for other thermal interrupt sources from
> > > same
> > > interrupt in therm-throt.c, where we do similar in offline path (by
> > > TGLX). If cpufreq offline can cause such issue of changing CPU,
> >
> > This is not cpufreq offline, but intel_pstate_update_status() which
> > may be triggered via sysfs. And again, the theoretically problematic
> > thing is dereferencing cpudata (which may be cleared by a remote CPU)
> > from the interrupt handler without protection.
>
> This will be a problem.
>
> >
> > > I can call intel_pstate_disable_hwp_interrupt() via override from
> > > https://elixir.bootlin.com/linux/latest/C/ident/thermal_throttle_offline
> > > after masking APIC interrupt.
> >
> > But why would using RCU be harder than this?
> I think, this will require all_cpu_data and cpu_data to be rcu
> protected. This needs to be well tested.
>
> I think better to revert the patch for the next release.
Done, thanks!
next prev parent reply other threads:[~2021-09-07 13:41 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-09-04 5:37 [PATCH] cpufreq: intel_pstate: Fix for HWP interrupt before driver is ready Srinivas Pandruvada
2021-09-06 16:17 ` Rafael J. Wysocki
2021-09-06 16:43 ` Jens Axboe
2021-09-06 16:54 ` Srinivas Pandruvada
2021-09-06 16:58 ` Rafael J. Wysocki
2021-09-06 17:23 ` Srinivas Pandruvada
2021-09-06 17:54 ` Rafael J. Wysocki
2021-09-06 18:14 ` Srinivas Pandruvada
2021-09-06 18:25 ` Rafael J. Wysocki
2021-09-06 19:56 ` Srinivas Pandruvada
2021-09-07 13:41 ` Rafael J. Wysocki [this message]
2021-09-06 16:53 ` Srinivas Pandruvada
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