From: Tejun Heo <tj@kernel.org>
To: Don Zickus <dzickus@redhat.com>
Cc: Ulrich Obergfell <uobergfe@redhat.com>,
Ingo Molnar <mingo@redhat.com>,
Peter Zijlstra <peterz@infradead.org>,
Andrew Morton <akpm@linux-foundation.org>,
linux-kernel@vger.kernel.org, kernel-team@fb.com
Subject: Re: [PATCH 2/2] workqueue: implement lockup detector
Date: Thu, 3 Dec 2015 14:43:58 -0500 [thread overview]
Message-ID: <20151203194358.GK27463@mtj.duckdns.org> (raw)
In-Reply-To: <20151203175024.GE27730@redhat.com>
Hello, Don.
On Thu, Dec 03, 2015 at 12:50:24PM -0500, Don Zickus wrote:
> This sort of looks like the hung task detector..
>
> I am a little concerned because we just made a big effort to properly
> separate the hardlockup and softlockup paths and yet retain the flexibility
> to enable/disable them separately. Now it seems the workqueue detector is
> permanently entwined with the softlockup detector. I am not entirely sure
> that is correct thing to do.
The only area they get entwined is how it's controlled from userland.
While it isn't quite the same as softlockup detection, I think what it
monitors is close enough that it makes sense to put them under the
same interface.
> It also seems awkward for the lockup code to have to jump to the workqueue
> code to function properly. :-/ Though we have made exceptions for the virt
> stuff and the workqueue code is simple..
Softlockup code doesn't depend on workqueue in any way. Workqueue
tags on touch_softlockup to detect cases which shouldn't be warned and
its enabledness is controlled together with softlockup and that's it.
> Actually, I am curious, it seems if you just added a
> /proc/sys/kernel/wq_watchdog entry, you could elminiate the entire need for
> modifying the watchdog code to begin with. As you really aren't using any
> of it other than piggybacking on the touch_softlockup_watchdog stuff, which
> could probably be easily added without all the extra enable/disable changes
> in watchdog.c.
Yeah, except for touch signal, it's purely interface thing. I don't
feel too strong about this but it seems a bit silly to introduce a
whole different set of interface for this. e.g. if the user wanted to
disable softlockup detection, it'd be weird to leave wq lockup
detection running. The same goes for threshold.
> Again, this looks like what the hung task detector is doing, which I
> struggled with years ago to integrate with the lockup code because in the
> end I had trouble re-using much of it.
So, it's a stall detector and there are inherent similarities but the
conditions tested are pretty different and it's a lot lighter. I'm
not really sure what you're meaning to say.
Thanks.
--
tejun
next prev parent reply other threads:[~2015-12-03 19:44 UTC|newest]
Thread overview: 40+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-12-03 0:28 [PATCH 1/2] watchdog: introduce touch_softlockup_watchdog_sched() Tejun Heo
2015-12-03 0:28 ` [PATCH 2/2] workqueue: implement lockup detector Tejun Heo
2015-12-03 14:49 ` Tejun Heo
2015-12-03 17:50 ` Don Zickus
2015-12-03 19:43 ` Tejun Heo [this message]
2015-12-03 20:12 ` Ulrich Obergfell
2015-12-03 20:54 ` Tejun Heo
2015-12-04 8:02 ` Ingo Molnar
2015-12-04 16:52 ` Don Zickus
2015-12-04 13:19 ` Ulrich Obergfell
2015-12-07 19:06 ` [PATCH v2 " Tejun Heo
2015-12-07 21:38 ` Don Zickus
2015-12-07 21:39 ` Tejun Heo
2015-12-08 16:00 ` Don Zickus
2015-12-08 16:31 ` Tejun Heo
2015-12-03 9:33 ` [PATCH 1/2] watchdog: introduce touch_softlockup_watchdog_sched() Peter Zijlstra
2015-12-03 10:00 ` Peter Zijlstra
2015-12-03 14:48 ` Tejun Heo
2015-12-03 15:04 ` Peter Zijlstra
2015-12-03 15:06 ` Tejun Heo
2015-12-03 19:26 ` [PATCH] workqueue: warn if memory reclaim tries to flush !WQ_MEM_RECLAIM workqueue Tejun Heo
2015-12-03 20:43 ` Peter Zijlstra
2015-12-03 20:56 ` Tejun Heo
2015-12-03 21:09 ` Peter Zijlstra
2015-12-03 22:04 ` Tejun Heo
2015-12-04 12:51 ` Peter Zijlstra
2015-12-07 15:58 ` Tejun Heo
2016-01-26 17:38 ` Thierry Reding
2016-01-28 10:12 ` Peter Zijlstra
2016-01-28 12:47 ` Thierry Reding
2016-01-28 12:48 ` Thierry Reding
2016-01-29 11:09 ` Tejun Heo
2016-01-29 15:17 ` Peter Zijlstra
2016-01-29 18:28 ` Tejun Heo
2016-01-29 10:59 ` [PATCH wq/for-4.5-fixes] workqueue: skip flush dependency checks for legacy workqueues Tejun Heo
2016-01-29 15:07 ` Thierry Reding
2016-01-29 18:32 ` Tejun Heo
2016-02-02 6:54 ` Archit Taneja
2016-03-10 15:12 ` [PATCH] workqueue: warn if memory reclaim tries to flush !WQ_MEM_RECLAIM workqueue Adrian Hunter
2016-03-11 17:52 ` Tejun Heo
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=20151203194358.GK27463@mtj.duckdns.org \
--to=tj@kernel.org \
--cc=akpm@linux-foundation.org \
--cc=dzickus@redhat.com \
--cc=kernel-team@fb.com \
--cc=linux-kernel@vger.kernel.org \
--cc=mingo@redhat.com \
--cc=peterz@infradead.org \
--cc=uobergfe@redhat.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;
as well as URLs for NNTP newsgroup(s).