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From: Petr Mladek <pmladek@suse.com>
To: Pingfan Liu <kernelfans@gmail.com>
Cc: linux-kernel@vger.kernel.org, Sumit Garg <sumit.garg@linaro.org>,
	Catalin Marinas <catalin.marinas@arm.com>,
	Will Deacon <will@kernel.org>, Ingo Molnar <mingo@redhat.com>,
	Arnaldo Carvalho de Melo <acme@kernel.org>,
	Mark Rutland <mark.rutland@arm.com>,
	Alexander Shishkin <alexander.shishkin@linux.intel.com>,
	Jiri Olsa <jolsa@redhat.com>, Namhyung Kim <namhyung@kernel.org>,
	Marc Zyngier <maz@kernel.org>,
	Julien Thierry <jthierry@redhat.com>,
	Kees Cook <keescook@chromium.org>,
	Masahiro Yamada <masahiroy@kernel.org>,
	Sami Tolvanen <samitolvanen@google.com>,
	Andrew Morton <akpm@linux-foundation.org>,
	Wang Qing <wangqing@vivo.com>,
	"Peter Zijlstra (Intel)" <peterz@infradead.org>,
	Santosh Sivaraj <santosh@fossix.org>
Subject: Re: [PATCH 3/5] kernel/watchdog: adapt the watchdog_hld interface for async model
Date: Thu, 16 Sep 2021 10:29:04 +0200	[thread overview]
Message-ID: <YUMAUE5RFJAtAS/z@alley> (raw)
In-Reply-To: <20210915035103.15586-4-kernelfans@gmail.com>

On Wed 2021-09-15 11:51:01, Pingfan Liu wrote:
> When lockup_detector_init()->watchdog_nmi_probe(), PMU may be not ready
> yet. E.g. on arm64, PMU is not ready until
> device_initcall(armv8_pmu_driver_init).  And it is deeply integrated
> with the driver model and cpuhp. Hence it is hard to push this
> initialization before smp_init().
> 
> But it is easy to take an opposite approach by enabling watchdog_hld to
> get the capability of PMU async.

This is another cryptic description. I have probably got it after
looking at the 5th patch (was not Cc :-(

> The async model is achieved by introducing an extra parameter notifier
> of watchdog_nmi_probe().

I would say that the code is horrible and looks too complex.

What about simply calling watchdog_nmi_probe() and
lockup_detector_setup() once again when watchdog_nmi_probe()
failed in lockup_detector_init()?

Or do not call lockup_detector_init() at all in
kernel_init_freeable() when PMU is not ready yet.

Best Regards,
Petr

  parent reply	other threads:[~2021-09-16  8:29 UTC|newest]

Thread overview: 21+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-09-15  3:50 [PATCH 0/5] watchdog_hld cleanup and async model for arm64 Pingfan Liu
2021-09-15  3:50 ` [PATCH 1/5] kernel/watchdog: remove useless WATCHDOG_DEFAULT Pingfan Liu
2021-09-15  3:51 ` [PATCH 2/5] kernel/watchdog_hld: clarify the condition in hardlockup_detector_event_create() Pingfan Liu
2021-09-15  4:06   ` Andrew Morton
2021-09-16  3:47     ` Pingfan Liu
2021-09-15 13:45   ` Peter Zijlstra
2021-09-16  3:57     ` Pingfan Liu
2021-09-16  8:02       ` Petr Mladek
2021-09-17 15:08         ` Pingfan Liu
2021-09-15  3:51 ` [PATCH 3/5] kernel/watchdog: adapt the watchdog_hld interface for async model Pingfan Liu
2021-09-15 14:02   ` Peter Zijlstra
2021-09-16  3:07     ` Pingfan Liu
2021-09-16  8:29   ` Petr Mladek [this message]
2021-09-16  8:36     ` Petr Mladek
2021-09-17 15:41       ` Pingfan Liu
2021-09-20  8:20         ` Petr Mladek
2021-09-22  4:26           ` Pingfan Liu
2021-09-17 14:43     ` Pingfan Liu
2021-09-15  3:51 ` [PATCH 4/5] kernel/watchdog_hld: simplify the detecting of hld watchdog Pingfan Liu
2021-09-15  3:51 ` [PATCH 5/5] arm64/watchdog_hld: enable hard lockup on arm64 platform Pingfan Liu
2021-09-17 15:11   ` Pingfan Liu

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