linux-kernel - Re: [PATCH 1/1] task_work: Add local_irq_enable() into task_work

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Date:	Sat, 13 Oct 2012 22:59:25 +1300
From:	Michael Cree <mcree@...on.net.nz>
To:	Linus Torvalds <torvalds@...ux-foundation.org>,
	Al Viro <viro@...iv.linux.org.uk>
Cc:	Oleg Nesterov <oleg@...hat.com>, dl8bcu@...bcu.de,
	peterz@...radead.org, mingo@...nel.org,
	linux-kernel@...r.kernel.org, linux-alpha@...r.kernel.org
Subject: Re: [PATCH 1/1] task_work: Add local_irq_enable() into task_work_run()

On Sat 13 October 2012 14:09:36 Linus Torvalds wrote:
> On Sat, Oct 13, 2012 at 1:03 AM, Oleg Nesterov <oleg@...hat.com> wrote:
> > arch/alpha and probably some other architectures call
> > do_notify_resume()->task_work_run() with irqs disabled.
> 
> I'm going to ignore this patch because I *hope* it is unnecessary
> after the pull from Al that I just did.
> 
> But if that turns out to be not the case, please holler. Torsten, you
> seem to be the one who reported this, can you check the current git
> tree?

I thought I might step in and run some tests.  Current git compiled for SMP 
generic Alpha and running on a 3-CPU ES45.  I have just managed to compile and 
run the test of eglibc without any RCU CPU task lockups!!  This is the first 
time in a couple or so years that I have seen a build of eglibc complete under 
an SMP kernel built for generic Alpha.

So, Al, you have made my day!

Any chance that we could have the fixes backported to the stable queue, in 
particular to the 3,2 kernel?  We should then be able to run the Debian built 
SMP kernel on the autobuilders at Debian-Ports rather than having to run a 
specially built kernel or a UP kernel.

BTW, the WARNING: at kernel/softirq.c:139 __local_bh_enable+0xe8/0x110() still 
occurs when bringing up the CPUs.  Actually it happens twice now.  I've 
attached my dmesg dump should you wish to check.

Cheers
Michael.

View attachment "dmesg-3.6.0-generic-10664-g4e21fc1-startup.txt" of type "text/plain" (22869 bytes)