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Re: [PATCH] random: Fix kernel panic due to system_wq use before init

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Hello, Linus.

On Wed, Sep 14, 2016 at 12:14:30PM -0700, Linus Torvalds wrote:
> I'm wondering if we couldn't just initialize "system_wq" earlier.
> Right now init_workqueues() is an "early_initcall()", so it's at the
> same priority as a number of other random early initcalls. My gut
> feeling is that it should be initialized even earlier, with the
> scheduler.
> 
> Because dammit, we use "schedule_work()" as if it was a pretty core
> scheduler thing, and having to have some odd knowledge of system_wq
> initialization details in the rest of the kernel sounds really really
> wrong.
> 
> I don't think the random code is at all special in maybe wanting to
> schedule some work despite being an "early" initcall.
> 
> Adding Tejun to the cc, and quoting the whole email.
> 
> Tejun, comments?

We've used keventd_up() for this purpose and it hasn't been big enough
an issue as workqueue usages during earlyboot are very rare (only five
users right now).  But, yeah, it's getting used a more and more and
there's no harm in moving it to earlier.  I'll see how early I can
push it.

Thanks.

-- 
tejun

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Thread

[PATCH] random: Fix kernel panic due to system_wq use before init Waiman Long <Waiman.Long@hpe.com> - 2016-09-14 21:10 +0200
  Re: [PATCH] random: Fix kernel panic due to system_wq use before init Linus Torvalds <torvalds@linux-foundation.org> - 2016-09-14 21:20 +0200
    Re: [PATCH] random: Fix kernel panic due to system_wq use before init Linus Torvalds <torvalds@linux-foundation.org> - 2016-09-14 23:10 +0200
    Re: [PATCH] random: Fix kernel panic due to system_wq use before init Matt Fleming <matt@codeblueprint.co.uk> - 2016-09-19 11:30 +0200
    Re: [PATCH] random: Fix kernel panic due to system_wq use before init Matt Fleming <matt@codeblueprint.co.uk> - 2016-09-19 14:50 +0200
      Re: [PATCH] random: Fix kernel panic due to system_wq use before init Matt Fleming <matt@codeblueprint.co.uk> - 2016-09-19 17:00 +0200
        Re: [PATCH] random: Fix kernel panic due to system_wq use before init Matt Fleming <matt@codeblueprint.co.uk> - 2016-09-20 16:10 +0200
  Re: [PATCH] random: Fix kernel panic due to system_wq use before init Linus Torvalds <torvalds@linux-foundation.org> - 2016-09-14 21:20 +0200
    Re: [PATCH] random: Fix kernel panic due to system_wq use before init Tejun Heo <tj@kernel.org> - 2016-09-14 22:00 +0200
      Re: [PATCH] random: Fix kernel panic due to system_wq use before init Tejun Heo <tj@kernel.org> - 2016-09-15 00:30 +0200

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