Date: Tue, 12 Mar 2013 21:13:51 +0100
From: Andi Kleen <andi@firstfloor.org>
To: Oleg Nesterov <oleg@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>,
        Andi Kleen <andi@firstfloor.org>,
        Lucas De Marchi <lucas.de.marchi@gmail.com>,
        Benjamin Herrenschmidt <benh@kernel.crashing.org>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        Paul Mackerras <paulus@samba.org>, david@gibson.dropbear.id.au,
        Kees Cook <keescook@chromium.org>,
        Serge Hallyn <serge.hallyn@canonical.com>,
        "Rafael J. Wysocki" <rjw@sisk.pl>,
        Andrew Morton <akpm@linux-foundation.org>,
        Feng Hong <hongfeng@marvell.com>,
        Lucas De Marchi <lucas.demarchi@profusion.mobi>
Subject: Re: Regression with orderly_poweroff()
Message-ID: <20130312201351.GF11268@two.firstfloor.org>
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> Btw. There is another "strange" user, arch/x86/kernel/cpu/mcheck/mce.c.
> It uses mce_trigger_work to call call_usermodehelper(UMH_NO_WAIT).
> Why? UMH_NO_WAIT is already atomic. And the !work_pending() check is
> confusing, schedule_work(schedule_work) checks it is not pending.

I think you're right, the additional step shouldn't be needed.

The MCE Handler uses the trick to do this in MCE context if the
interrupts were enabled earlier. 

-Andi

-- 
ak@linux.intel.com -- Speaking for myself only.
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