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>,
npiggin@gmail.com, davem@davemloft.net,
Marc Zyngier <maz@kernel.org>, Stephen Boyd <swboyd@chromium.org>,
sparclinux@vger.kernel.org, christophe.leroy@csgroup.eu,
Catalin Marinas <catalin.marinas@arm.com>,
ravi.v.shankar@intel.com, Randy Dunlap <rdunlap@infradead.org>,
Pingfan Liu <kernelfans@gmail.com>,
Guenter Roeck <groeck@chromium.org>,
Lecopzer Chen <lecopzer.chen@mediatek.com>,
Ian Rogers <irogers@google.com>,
ito-yuichi@fujitsu.com, ricardo.neri@intel.com,
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 13/18] watchdog/hardlockup: Have the perf hardlockup use __weak functions more cleanly
Date: Wed, 24 May 2023 15:59:15 +0200 [thread overview]
Message-ID: <ZG4YMyifGLOBJxLo@alley> (raw)
In-Reply-To: <20230519101840.v5.13.I847d9ec852449350997ba00401d2462a9cb4302b@changeid>
On Fri 2023-05-19 10:18:37, Douglas Anderson wrote:
> The fact that there watchdog_hardlockup_enable(),
> watchdog_hardlockup_disable(), and watchdog_hardlockup_probe() are
> declared __weak means that the configured hardlockup detector can
> define non-weak versions of those functions if it needs to. Instead of
> doing this, the perf hardlockup detector hooked itself into the
> default __weak implementation, which was a bit awkward. Clean this up.
>
> >From comments, it looks as if the original design was done because the
> __weak function were expected to implemented by the architecture and
> not by the configured hardlockup detector. This got awkward when we
> tried to add the buddy lockup detector which was not arch-specific but
> wanted to hook into those same functions.
>
> This is not expected to have any functional impact.
>
> @@ -187,27 +187,33 @@ static inline void watchdog_hardlockup_kick(void) { }
> #endif /* !CONFIG_HARDLOCKUP_DETECTOR_PERF */
>
> /*
> - * These functions can be overridden if an architecture implements its
> - * own hardlockup detector.
> + * These functions can be overridden based on the configured hardlockdup detector.
> *
> * watchdog_hardlockup_enable/disable can be implemented to start and stop when
> - * softlockup watchdog start and stop. The arch must select the
> + * softlockup watchdog start and stop. The detector must select the
> * SOFTLOCKUP_DETECTOR Kconfig.
> */
> -void __weak watchdog_hardlockup_enable(unsigned int cpu)
> -{
> - hardlockup_detector_perf_enable();
> -}
> +void __weak watchdog_hardlockup_enable(unsigned int cpu) { }
>
> -void __weak watchdog_hardlockup_disable(unsigned int cpu)
> -{
> - hardlockup_detector_perf_disable();
> -}
> +void __weak watchdog_hardlockup_disable(unsigned int cpu) { }
>
> /* Return 0, if a hardlockup watchdog is available. Error code otherwise */
> int __weak __init watchdog_hardlockup_probe(void)
> {
> - return hardlockup_detector_perf_init();
> + /*
> + * If CONFIG_HAVE_NMI_WATCHDOG is defined then an architecture
> + * is assumed to have the hard watchdog available and we return 0.
> + */
> + if (IS_ENABLED(CONFIG_HAVE_NMI_WATCHDOG))
> + return 0;
> +
> + /*
> + * Hardlockup detectors other than those using CONFIG_HAVE_NMI_WATCHDOG
> + * are required to implement a non-weak version of this probe function
> + * to tell whether they are available. If they don't override then
> + * we'll return -ENODEV.
> + */
> + return -ENODEV;
> }
When thinking more about it. It is weird that we need to handle
CONFIG_HAVE_NMI_WATCHDOG in this default week function.
It should be handled in watchdog_hardlockup_probe() implemented
in kernel/watchdog_perf.c.
IMHO, the default __weak function could always return -ENODEV;
Would it make sense, please?
Best Regards,
Petr
next prev parent reply other threads:[~2023-05-24 13:59 UTC|newest]
Thread overview: 38+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-05-19 17:18 [PATCH v5 00/18] watchdog/hardlockup: Add the buddy hardlockup detector Douglas Anderson
2023-05-19 17:18 ` [PATCH v5 01/18] watchdog/perf: Define dummy watchdog_update_hrtimer_threshold() on correct config Douglas Anderson
2023-05-19 17:18 ` [PATCH v5 02/18] watchdog/perf: More properly prevent false positives with turbo modes Douglas Anderson
2023-05-23 9:35 ` Petr Mladek
2023-05-19 17:18 ` [PATCH v5 03/18] watchdog: remove WATCHDOG_DEFAULT Douglas Anderson
2023-05-19 17:18 ` [PATCH v5 04/18] watchdog/hardlockup: change watchdog_nmi_enable() to void Douglas Anderson
2023-05-19 17:18 ` [PATCH v5 05/18] watchdog/perf: Ensure CPU-bound context when creating hardlockup detector event Douglas Anderson
2023-05-19 17:18 ` [PATCH v5 06/18] watchdog/hardlockup: Add comments to touch_nmi_watchdog() Douglas Anderson
2023-05-23 9:58 ` Petr Mladek
2023-05-19 17:18 ` [PATCH v5 07/18] watchdog/perf: Rename watchdog_hld.c to watchdog_perf.c Douglas Anderson
2023-05-19 17:18 ` [PATCH v5 08/18] watchdog/hardlockup: Move perf hardlockup checking/panic to common watchdog.c Douglas Anderson
2023-05-23 11:45 ` Petr Mladek
2023-05-19 17:18 ` [PATCH v5 09/18] watchdog/hardlockup: Style changes to watchdog_hardlockup_check() / is_hardlockup() Douglas Anderson
2023-05-19 17:18 ` [PATCH v5 10/18] watchdog/hardlockup: Add a "cpu" param to watchdog_hardlockup_check() Douglas Anderson
2023-05-23 16:02 ` Petr Mladek
2023-05-23 16:34 ` Doug Anderson
2023-05-24 11:36 ` Petr Mladek
2023-05-19 17:18 ` [PATCH v5 11/18] watchdog/hardlockup: Move perf hardlockup watchdog petting to watchdog.c Douglas Anderson
2023-05-24 13:07 ` Petr Mladek
2023-05-19 17:18 ` [PATCH v5 12/18] watchdog/hardlockup: Rename some "NMI watchdog" constants/function Douglas Anderson
2023-05-24 13:38 ` Petr Mladek
2023-05-25 23:33 ` Doug Anderson
2023-05-19 17:18 ` [PATCH v5 13/18] watchdog/hardlockup: Have the perf hardlockup use __weak functions more cleanly Douglas Anderson
2023-05-24 13:59 ` Petr Mladek [this message]
2023-05-24 19:38 ` Doug Anderson
2023-05-26 14:44 ` Petr Mladek
2023-05-19 17:18 ` [PATCH v5 14/18] watchdog/hardlockup: detect hard lockups using secondary (buddy) CPUs Douglas Anderson
2023-05-25 16:26 ` Petr Mladek
2023-05-25 20:08 ` Doug Anderson
2023-05-26 12:29 ` Petr Mladek
2023-05-19 17:18 ` [PATCH v5 15/18] watchdog/perf: Add a weak function for an arch to detect if perf can use NMIs Douglas Anderson
2023-05-26 12:36 ` Petr Mladek
2023-06-12 10:33 ` Mark Rutland
2023-06-12 13:55 ` Doug Anderson
2023-06-12 13:59 ` Mark Rutland
2023-05-19 17:18 ` [PATCH v5 16/18] watchdog/perf: Adapt the watchdog_perf interface for async model Douglas Anderson
2023-05-19 17:18 ` [PATCH v5 17/18] arm64: add hw_nmi_get_sample_period for preparation of lockup detector Douglas Anderson
2023-05-19 17:18 ` [PATCH v5 18/18] arm64: Enable perf events based hard " Douglas Anderson
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