LKML Archive on lore.kernel.org
help / color / mirror / Atom feed
From: Pingfan Liu <piliu@redhat.com>
To: Petr Mladek <pmladek@suse.com>
Cc: Pingfan Liu <kernelfans@gmail.com>,
	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: Fri, 17 Sep 2021 22:43:52 +0800	[thread overview]
Message-ID: <YUSpqCqA4jLboCVP@piliu.users.ipa.redhat.com> (raw)
In-Reply-To: <YUMAUE5RFJAtAS/z@alley>

On Thu, Sep 16, 2021 at 10:29:04AM +0200, Petr Mladek wrote:
> 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()?
> 
It may work. But there is still a way to report the PMU NMI capability
to watchdog layer accurately. And the API should be extened somehow.

I am thinking something, maybe I can model in another way.
> Or do not call lockup_detector_init() at all in
> kernel_init_freeable() when PMU is not ready yet.
> 

This may be not a good choice. Since lockup_detector_init() had better
be ready as early as possible, especially before drivers.


Thanks,

	Pingfan


  parent reply	other threads:[~2021-09-17 14:45 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
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 [this message]
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

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=YUSpqCqA4jLboCVP@piliu.users.ipa.redhat.com \
    --to=piliu@redhat.com \
    --cc=acme@kernel.org \
    --cc=akpm@linux-foundation.org \
    --cc=alexander.shishkin@linux.intel.com \
    --cc=catalin.marinas@arm.com \
    --cc=jolsa@redhat.com \
    --cc=jthierry@redhat.com \
    --cc=keescook@chromium.org \
    --cc=kernelfans@gmail.com \
    --cc=linux-kernel@vger.kernel.org \
    --cc=mark.rutland@arm.com \
    --cc=masahiroy@kernel.org \
    --cc=maz@kernel.org \
    --cc=mingo@redhat.com \
    --cc=namhyung@kernel.org \
    --cc=peterz@infradead.org \
    --cc=pmladek@suse.com \
    --cc=samitolvanen@google.com \
    --cc=santosh@fossix.org \
    --cc=sumit.garg@linaro.org \
    --cc=wangqing@vivo.com \
    --cc=will@kernel.org \
    --subject='Re: [PATCH 3/5] kernel/watchdog: adapt the watchdog_hld interface for async model' \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link

This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).