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 15/18] watchdog/perf: Add a weak function for an arch to detect if perf can use NMIs
Date: Fri, 26 May 2023 14:36:50 +0200 [thread overview]
Message-ID: <ZHCn4hNxFpY5-9Ki@alley> (raw)
In-Reply-To: <20230519101840.v5.15.Ic55cb6f90ef5967d8aaa2b503a4e67c753f64d3a@changeid>
On Fri 2023-05-19 10:18:39, Douglas Anderson wrote:
> On arm64, NMI support needs to be detected at runtime. Add a weak
> function to the perf hardlockup detector so that an architecture can
> implement it to detect whether NMIs are available.
>
> Signed-off-by: Douglas Anderson <dianders@chromium.org>
> ---
> While I won't object to this patch landing, I consider it part of the
> arm64 perf hardlockup effort. I would be OK with the earlier patches
> in the series landing and then not landing ${SUBJECT} patch nor
> anything else later.
>
> I'll also note that, as an alternative to this, it would be nice if we
> could figure out how to make perf_event_create_kernel_counter() fail
> on arm64 if NMIs aren't available. Maybe we could add a "must_use_nmi"
> element to "struct perf_event_attr"?
>
> --- a/kernel/watchdog_perf.c
> +++ b/kernel/watchdog_perf.c
> @@ -234,12 +234,22 @@ void __init hardlockup_detector_perf_restart(void)
> }
> }
>
> +bool __weak __init arch_perf_nmi_is_available(void)
> +{
> + return true;
> +}
> +
> /**
> * watchdog_hardlockup_probe - Probe whether NMI event is available at all
> */
> int __init watchdog_hardlockup_probe(void)
> {
> - int ret = hardlockup_detector_event_create();
> + int ret;
> +
> + if (!arch_perf_nmi_is_available())
> + return -ENODEV;
My understanding is that this would block the perf hardlockup detector
at runtime. Does it work with the "nmi_watchdog" sysctl. I see
that it is made read-only when it is not enabled at build time,
see NMI_WATCHDOG_SYSCTL_PERM.
> +
> + ret = hardlockup_detector_event_create();
>
> if (ret) {
> pr_info("Perf NMI watchdog permanently disabled\n");
Best Regards,
Petr
next prev parent reply other threads:[~2023-05-26 12:36 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
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 [this message]
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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