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Date: Tue, 9 Feb 2016 08:39:15 -0800
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Subject: Re: Crashes with 874bbfe600a6 in 3.18.25
From: Linus Torvalds <torvalds@linux-foundation.org>
To: Mike Galbraith <umgwanakikbuti@gmail.com>
Cc: Tejun Heo <tj@kernel.org>, Michal Hocko <mhocko@kernel.org>,
        Jiri Slaby <jslaby@suse.cz>, Thomas Gleixner <tglx@linutronix.de>,
        Petr Mladek <pmladek@suse.com>, Jan Kara <jack@suse.cz>,
        Ben Hutchings <ben@decadent.org.uk>,
        Sasha Levin <sasha.levin@oracle.com>, Shaohua Li <shli@fb.com>,
        LKML <linux-kernel@vger.kernel.org>, stable <stable@vger.kernel.org>,
        Daniel Bilik <daniel.bilik@neosystem.cz>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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On Tue, Feb 9, 2016 at 7:31 AM, Mike Galbraith <umgwanakikbuti@gmail.com> wrote:
> On Fri, 2016-02-05 at 16:06 -0500, Tejun Heo wrote:
>> >
>> > That 874bbfe6 should die.
>>
>> Yeah, it's gonna be killed.  The commit is there because the behavior
>> change broke things.  We don't want to guarantee it but have been and
>> can't change it right away just because we don't like it when things
>> may break from it.  The plan is to implement a debug option to force
>> workqueue to always execute these work items on a foreign cpu to weed
>> out breakages.
>
> A niggling question remaining is when is it gonna be killed?

It probably should be killed sooner rather than later.

Just document that if you need something to run on a _particular_ cpu,
you need to use "schedule_delayed_work_on()" and "add_timer_on()".

The proper fix was 176bed1de5bf, and 874bbfe6 was just wrong.

                 Linus