linux-kernel - Re: Linux 3.19-rc5

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Message-ID: <1456360.Y3S5fhtEMe@vostro.rjw.lan>
Date:	Fri, 30 Jan 2015 03:06:11 +0100
From:	"Rafael J. Wysocki" <rjw@...ysocki.net>
To:	Linus Torvalds <torvalds@...ux-foundation.org>
Cc:	Ingo Molnar <mingo@...nel.org>,
	Peter Hurley <peter@...leysoftware.com>,
	Davidlohr Bueso <dave@...olabs.net>,
	Peter Zijlstra <peterz@...radead.org>,
	Bruno Prémont <bonbons@...ux-vserver.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ilya Dryomov <ilya.dryomov@...tank.com>,
	Mike Galbraith <umgwanakikbuti@...il.com>,
	Oleg Nesterov <oleg@...hat.com>
Subject: Re: Linux 3.19-rc5

On Thursday, January 29, 2015 05:25:07 PM Linus Torvalds wrote:
> On Thu, Jan 29, 2015 at 5:12 PM, Linus Torvalds
> <torvalds@...ux-foundation.org> wrote:
> >
> > The WARN() was already changed to a WARN_ONCE().
> 
> Oh, but I notice that the "__set_current_state(TASK_RUNNING) ends up
> always happening.
> 
> So I think the right fix is to:
> 
>  - warn once like we do
> 
>  - but *not* do that __set_current_state() which was always total crap anyway
> 
> Why do I say "total crap"? Because of two independent issues:
> 
>  (a) it actually changes behavior for a debug vs non-debug kernel,
> which is a really bad idea to begin with
> 
>  (b) it's really wrong. The whole "nested sleep" case was never a
> major bug to begin with, just a possible inefficiency where constant
> nested sleeps would possibly make the outer sleep not sleep. But that
> "could possibly make" case was the unlikely case, and the debug patch
> made it happen *all* the time by explicitly setting things running.
> 
> So I think the proper patch is the attached.

I applied the patch and compiled the kernel with CONFIG_DEBUG_ATOMIC_SLEEP
set again.  The warning is back, so the DEBUG_ATOMIC_SLEEP thing appears to
be working (and I don't really care about the freaking warning anyway), but the
pccardd load issue is gone, so the patch fixes the problem for me.  Thanks!

Rafael

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