From: Oleg Nesterov <oleg@redhat.com>
To: Michal Hocko <mhocko@kernel.org>
Cc: syzbot <syzbot+b70f2aabc707c69c9239@syzkaller.appspotmail.com>,
chanho.min@lge.com, linux-fsdevel@vger.kernel.org,
linux-kernel@vger.kernel.org, pavel@ucw.cz,
rafael.j.wysocki@intel.com, syzkaller-bugs@googlegroups.com,
viro@zeniv.linux.org.uk
Subject: Re: WARNING: syz-executor still has locks held!
Date: Wed, 20 Mar 2019 16:00:54 +0100 [thread overview]
Message-ID: <20190320150053.GD21673@redhat.com> (raw)
In-Reply-To: <20190320132936.GB8696@dhcp22.suse.cz>
On 03/20, Michal Hocko wrote:
>
> On Wed 20-03-19 14:24:11, Oleg Nesterov wrote:
> > On 03/20, Michal Hocko wrote:
> > >
> > > Yes we do hold the cgred mutex while calling freezable_schedule but why
> > > are we getting a warning is not really clear to me. The task should be
> > > hidden from the freezer so why do we warn at all?
> >
> > try_to_freeze() calls debug_check_no_locks_held() and this makes sense.
>
> Yes it does. But it already ignores PF_NOFREEZE tasks and I fail to see
> why is PF_FREEZER_SKIP any different.
But they differ. PF_NOFREEZE is a "sticky" flag for kthreads. Set by default,
cleared by set_freezable() if you want a freezable kthread.
PF_FREEZER_SKIP means that a sleeping freezable task will call try_to_freeze()
right after schedule() returns, so try_to_freeze_tasks() can safely count it as
"already frozen".
> it seems that skipping the task was the only viable option
> to fix suspend issues
Yes, de_thread() should use freezable_schedule(), iow I hope we will reconsider
this (reverted) patch.
> as removing the cgred is way way too complicated.
We need to do this anyway, this leads to other more serious problems...
Oleg.
next prev parent reply other threads:[~2019-03-20 15:01 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-11-24 17:40 WARNING: syz-executor still has locks held! syzbot
2019-03-20 12:24 ` syzbot
2019-03-20 13:16 ` Michal Hocko
2019-03-20 13:24 ` Oleg Nesterov
2019-03-20 13:29 ` Michal Hocko
2019-03-20 15:00 ` Oleg Nesterov [this message]
2019-03-20 15:12 ` Michal Hocko
2019-03-20 17:30 ` Oleg Nesterov
2019-03-20 19:45 ` Michal Hocko
2019-03-20 20:32 ` Michal Hocko
2019-03-21 17:28 ` Oleg Nesterov
2019-03-22 10:36 ` Michal Hocko
2019-03-22 10:35 ` Pavel Machek
2019-03-20 13:18 ` Oleg Nesterov
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