Re: [PATCH v5 08/18] watchdog/hardlockup: Move perf hardlockup checking/panic to common watchdog.c

From: Petr Mladek <pmladek@suse.com>
To: Douglas Anderson <dianders@chromium.org>
Cc: Andrew Morton <akpm@linux-foundation.org>,
	Matthias Kaehlcke <mka@chromium.org>,
	kgdb-bugreport@lists.sourceforge.net,
	Stephane Eranian <eranian@google.com>,
	mpe@ellerman.id.au, Tzung-Bi Shih <tzungbi@chromium.org>,
	Daniel Thompson <daniel.thompson@linaro.org>,
	Mark Rutland <mark.rutland@arm.com>,
	linuxppc-dev@lists.ozlabs.org, Sumit Garg <sumit.garg@linaro.org>,
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	linux-arm-kernel@lists.infradead.org,
	linux-perf-users@vger.kernel.org, Will Deacon <will@kernel.org>,
	Chen-Yu Tsai <wens@csie.org>,
	linux-kernel@vger.kernel.org,
	Masayoshi Mizuma <msys.mizuma@gmail.com>,
	Andi Kleen <ak@linux.intel.com>
Subject: Re: [PATCH v5 08/18] watchdog/hardlockup: Move perf hardlockup checking/panic to common watchdog.c
Date: Tue, 23 May 2023 13:45:40 +0200	[thread overview]
Message-ID: <ZGynZJ6Kvf1w7Pyu@alley> (raw)
In-Reply-To: <20230519101840.v5.8.Id4133d3183e798122dc3b6205e7852601f289071@changeid>

On Fri 2023-05-19 10:18:32, Douglas Anderson wrote:
> The perf hardlockup detector works by looking at interrupt counts and
> seeing if they change from run to run. The interrupt counts are
> managed by the common watchdog code via its watchdog_timer_fn().
> 
> Currently the API between the perf detector and the common code is a
> function: is_hardlockup(). When the hard lockup detector sees that
> function return true then it handles printing out debug info and
> inducing a panic if necessary.
> 
> Let's change the API a little bit in preparation for the buddy
> hardlockup detector. The buddy hardlockup detector wants to print
> nearly the same debug info and have nearly the same panic
> behavior. That means we want to move all that code to the common
> file. For now, the code in the common file will only be there if the
> perf hardlockup detector is enabled, but eventually it will be
> selected by a common config.
> 
> Right now, this _just_ moves the code from the perf detector file to
> the common file and changes the names. It doesn't make the changes
> that the buddy hardlockup detector will need and doesn't do any style
> cleanups. A future patch will do cleanup to make it more obvious what
> changed.
> 
> With the above, we no longer have any callers of is_hardlockup()
> outside of the "watchdog.c" file, so we can remove it from the header,
> make it static, and move it to the same "#ifdef" block as our new
> watchdog_hardlockup_check(). While doing this, it can be noted that
> even if no hardlockup detectors were configured the existing code used
> to still have the code for counting/checking "hrtimer_interrupts" even
> if the perf hardlockup detector wasn't configured. We didn't need to
> do that, so move all the "hrtimer_interrupts" counting to only be
> there if the perf hardlockup detector is configured as well.
> 
> This change is expected to be a no-op.
> 
> Signed-off-by: Douglas Anderson <dianders@chromium.org>

Reviewed-by: Petr Mladek <pmladek@suse.com>

Best Regards,
Petr