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From: Mikulas Patocka <mpatocka@redhat.com>
To: Mike Snitzer <snitzer@redhat.com>
Cc: Jens Axboe <axboe@kernel.dk>, Kent Overstreet <kmo@daterainc.com>,
	"Alasdair G. Kergon" <agk@redhat.com>,
	linux-kernel@vger.kernel.org, dm-devel@redhat.com
Subject: Re: block: flush queued bios when the process blocks
Date: Tue, 6 Oct 2015 10:26:48 -0400 (EDT)	[thread overview]
Message-ID: <alpine.LRH.2.02.1510061020200.20214@file01.intranet.prod.int.rdu2.redhat.com> (raw)
In-Reply-To: <20151006134753.GA30555@redhat.com>



On Tue, 6 Oct 2015, Mike Snitzer wrote:

> On Tue, Oct 06 2015 at  9:28am -0400,
> Mikulas Patocka <mpatocka@redhat.com> wrote:
> 
> > 
> > 
> > On Mon, 5 Oct 2015, Mike Snitzer wrote:
> > 
> > > Mikulas,
> > > 
> > > Could it be that cond_resched() wasn't unplugging?  As was
> > > recently raised in this thread: https://lkml.org/lkml/2015/9/18/378
> > > Chris Mason's patch from that thread fixed this	issue... I _think_ Linus
> > > has since committed Chris' work but I haven't kept my finger on the
> > > pulse of that issue.
> > 
> > I think it doesn't matter (regarding correctness) if cond_reched unplugs 
> > on not. If it didn't unplug, the process will be scheduled later, and it 
> > will eventually reach the point where it unplugs.
> 
> Couldn't the original deadlock you fixed (as described in your first
> patch) manifest when a new process is scheduled?

A process rescheduled with cond_reched is not stuck, it will be run later. 
It may contribute to increased request latency, but it can't contribute to 
a deadlock.

Mikulas

  parent reply	other threads:[~2015-10-06 14:26 UTC|newest]

Thread overview: 42+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2014-05-27 15:03 [PATCH] block: flush queued bios when the process blocks Mikulas Patocka
2014-05-27 15:08 ` Jens Axboe
2014-05-27 15:23   ` Mikulas Patocka
2014-05-27 15:42     ` Jens Axboe
2014-05-27 16:26       ` Mikulas Patocka
2014-05-27 17:33         ` Mike Snitzer
2014-05-27 19:56           ` Kent Overstreet
2015-10-05 19:50             ` Mike Snitzer
2014-05-27 17:42         ` [PATCH] " Jens Axboe
2014-05-27 18:14           ` [dm-devel] " Christoph Hellwig
2014-05-27 19:59             ` Kent Overstreet
2014-05-27 19:56           ` Mikulas Patocka
2014-05-27 20:06             ` Kent Overstreet
2014-05-29 23:52           ` Mikulas Patocka
2015-10-05 20:59             ` Mike Snitzer
2015-10-06 13:28               ` Mikulas Patocka
2015-10-06 13:47                 ` Mike Snitzer
2015-10-06 14:10                   ` Mikulas Patocka
2015-10-06 14:26                   ` Mikulas Patocka [this message]
2015-10-06 18:17               ` [dm-devel] " Mikulas Patocka
2015-10-06 18:50                 ` Mike Snitzer
2015-10-06 20:16                   ` [PATCH v2] " Mike Snitzer
2015-10-06 20:26                     ` Mike Snitzer
2015-10-08 15:04                     ` Mikulas Patocka
2015-10-08 15:08                       ` Mike Snitzer
2015-10-09 19:52                         ` Mike Snitzer
2015-10-09 19:59                           ` Mike Snitzer
2015-10-14 20:47                             ` [PATCH v3 for-4.4] block: flush queued bios when process blocks to avoid deadlock Mike Snitzer
2015-10-14 21:44                               ` Jeff Moyer
2015-10-17 16:04                               ` Ming Lei
2015-10-20 19:57                                 ` Mike Snitzer
2015-10-20 20:03                                 ` Mikulas Patocka
2015-10-21 16:38                                   ` Ming Lei
2015-10-21 21:49                                     ` Mikulas Patocka
2015-10-22  1:53                                       ` Ming Lei
2015-10-15  3:27                           ` [PATCH v2] block: flush queued bios when the process blocks Ming Lei
2015-10-15  8:06                             ` Mike Snitzer
2015-10-16  3:08                               ` Ming Lei
2015-10-16 15:29                                 ` Mike Snitzer
2015-10-17 15:54                                   ` Ming Lei
2015-10-09 11:58                     ` kbuild test robot
2014-05-27 17:59   ` [PATCH] " Kent Overstreet

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