From: Michal Hocko <mhocko@kernel.org>
To: Christoph Lameter <cl@linux.com>
Cc: Sasha Levin <sasha.levin@oracle.com>,
LKML <linux-kernel@vger.kernel.org>,
"linux-mm@kvack.org" <linux-mm@kvack.org>,
Andrew Morton <akpm@linux-foundation.org>
Subject: Re: mm, vmstat: kernel BUG at mm/vmstat.c:1408!
Date: Thu, 21 Jan 2016 17:51:49 +0100 [thread overview]
Message-ID: <20160121165148.GF29520@dhcp22.suse.cz> (raw)
In-Reply-To: <alpine.DEB.2.20.1601210941540.7063@east.gentwo.org>
On Thu 21-01-16 09:45:12, Christoph Lameter wrote:
> On Thu, 21 Jan 2016, Michal Hocko wrote:
[...]
> > The vmstat update might be still waiting for its timer, idle mode started
> > and kick vmstat_update which might cpumask_test_and_set_cpu. Once the
> > idle terminates and the originally schedule vmstate_update executes it
> > sees the bit set and BUG_ON.
>
> Ok so we are going into idle mode and the vmstat_update timer is pending.
> Then the timer will not fire since going idle switches preemption off.
> quiet_vmstat will run without the chance of running vmstat_update
>
> We could be going idle and not have disabled preemption yet. Then
> vmstat_update will run. On return to the idling operation preemption will
> be disabled and quiet_vmstat() will be run.
>
> I do not see how these two things could race.
It goes like this:
CPU0: CPU1
vmstat_update
cpumask_test_and_set_cpu (0->1)
[...]
vmstat_shepherd
<enter idle> cpumask_test_and_clear_cpu(CPU0) (1->0)
quiet_vmstat
cpumask_test_and_set_cpu (0->1)
queue_delayed_work_on(CPU0)
refresh_cpu_vm_stats()
[...]
vmstat_update
nothing_to_do
cpumask_test_and_set_cpu (1->1)
VM_BUG_ON
Or am I missing something?
--
Michal Hocko
SUSE Labs
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next prev parent reply other threads:[~2016-01-21 16:51 UTC|newest]
Thread overview: 38+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-12-19 0:33 mm, vmstat: kernel BUG at mm/vmstat.c:1408! Sasha Levin
2015-12-21 13:08 ` Christoph Lameter
2015-12-21 20:28 ` Sasha Levin
2015-12-21 21:07 ` Sasha Levin
2015-12-21 21:14 ` Christoph Lameter
2015-12-22 17:21 ` Christoph Lameter
2015-12-24 20:14 ` Sasha Levin
2015-12-29 17:01 ` Christoph Lameter
2015-12-29 17:18 ` Christoph Lameter
2016-01-04 18:05 ` Christoph Lameter
2016-01-04 18:46 ` Sasha Levin
2016-01-12 11:31 ` Shiraz Hashim
2016-01-12 12:23 ` Christoph Lameter
2016-01-12 12:27 ` Shiraz Hashim
2016-01-13 11:36 ` Shiraz Hashim
2016-01-13 12:32 ` Shiraz Hashim
2016-01-14 21:06 ` Sasha Levin
2016-01-20 14:37 ` Michal Hocko
2016-01-20 14:56 ` Sasha Levin
2016-01-20 15:10 ` Michal Hocko
2016-01-20 15:20 ` Christoph Lameter
2016-01-20 15:49 ` Sasha Levin
2016-01-20 15:55 ` Christoph Lameter
2016-01-20 21:28 ` Michal Hocko
2016-01-20 21:57 ` Christoph Lameter
2016-01-21 8:24 ` Michal Hocko
2016-01-21 15:45 ` Christoph Lameter
2016-01-21 16:51 ` Michal Hocko [this message]
2016-01-21 17:38 ` Christoph Lameter
2016-01-22 11:00 ` Shiraz Hashim
2016-01-22 14:04 ` Michal Hocko
2016-01-22 16:07 ` Christoph Lameter
2016-01-22 16:12 ` Michal Hocko
2016-01-22 16:46 ` Christoph Lameter
2016-01-22 17:12 ` Michal Hocko
2016-01-24 16:57 ` Linus Torvalds
2016-01-20 15:14 ` Christoph Lameter
2016-01-20 15:20 ` Michal Hocko
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