From: Petr Mladek <pmladek@suse.com>
To: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>,
Ingo Molnar <mingo@kernel.org>,
Laurence Oberman <loberman@redhat.com>,
Vincent Whitchurch <vincent.whitchurch@axis.com>,
Michal Hocko <mhocko@suse.com>,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH 1/3] watchdog/softlockup: Preserve original timestamp when touching watchdog externally
Date: Mon, 21 Oct 2019 15:04:25 +0200 [thread overview]
Message-ID: <20191021130425.ewiegm2425hkydb3@pathway.suse.cz> (raw)
In-Reply-To: <20191021124214.GD1817@hirez.programming.kicks-ass.net>
On Mon 2019-10-21 14:42:14, Peter Zijlstra wrote:
> On Mon, Aug 19, 2019 at 12:47:30PM +0200, Petr Mladek wrote:
> > Some bug report included the same softlockups in flush_tlb_kernel_range()
> > in regular intervals. Unfortunately was not clear if there was a progress
> > or not.
> >
> > The situation can be simulated with a simply busy loop:
> >
> > while (true)
> > cpu_relax();
> >
> > The softlockup detector produces:
> >
> > [ 168.277520] watchdog: BUG: soft lockup - CPU#1 stuck for 22s! [cat:4865]
> > [ 196.277604] watchdog: BUG: soft lockup - CPU#1 stuck for 22s! [cat:4865]
> > [ 236.277522] watchdog: BUG: soft lockup - CPU#1 stuck for 23s! [cat:4865]
> >
> > One would expect only one softlockup report or several reports with
> > an increased duration.
>
> Let's just say our expectations differ.
>
> > The result is that each softlockup is reported only once unless
> > another process get scheduled:
> >
> > [ 320.248948] watchdog: BUG: soft lockup - CPU#2 stuck for 26s! [cat:4916]
>
> Which would greatly confuse me; as the above would have me think the
> situation got resolved (no more lockups reported) even though it is
> still very much stuck there.
>
> IOW, I don't see how this makes anything better. You're removing
> information.
The 2nd patch brings back the regular report but with correctly
counted time (stuck for XXs).
I split it into two patches because I was not sure what would be
preferred behavior. I prefer the regular reports as well.
Best Regards,
Petr
next prev parent reply other threads:[~2019-10-21 13:04 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-08-19 10:47 [PATCH 0/3] watchdog/softlockup: Make softlockup reports more reliable and useful Petr Mladek
2019-08-19 10:47 ` [PATCH 1/3] watchdog/softlockup: Preserve original timestamp when touching watchdog externally Petr Mladek
2019-10-21 12:42 ` Peter Zijlstra
2019-10-21 13:04 ` Petr Mladek [this message]
2019-08-19 10:47 ` [PATCH 2/3] watchdog/softlockup: Report the same softlockup regularly Petr Mladek
2019-10-21 12:43 ` Peter Zijlstra
2019-10-21 13:40 ` Petr Mladek
2019-10-21 14:09 ` Peter Zijlstra
2019-08-19 10:47 ` [PATCH 3/3] Test softlockup Petr Mladek
2019-10-21 12:45 ` Peter Zijlstra
2019-10-21 13:06 ` Petr Mladek
2019-10-21 12:32 ` [PATCH 0/3] watchdog/softlockup: Make softlockup reports more reliable and useful Petr Mladek
-- strict thread matches above, loose matches on Subject: below --
2019-06-05 14:09 [RFC " Petr Mladek
2019-06-05 14:09 ` [PATCH 1/3] watchdog/softlockup: Preserve original timestamp when touching watchdog externally Petr Mladek
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=20191021130425.ewiegm2425hkydb3@pathway.suse.cz \
--to=pmladek@suse.com \
--cc=linux-kernel@vger.kernel.org \
--cc=loberman@redhat.com \
--cc=mhocko@suse.com \
--cc=mingo@kernel.org \
--cc=peterz@infradead.org \
--cc=tglx@linutronix.de \
--cc=vincent.whitchurch@axis.com \
/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
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox
all inboxes | Powered by JetHome®