linux-kernel - Re: pstore: change mutex locking to spin

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Message-ID: <1313617679.2212.4.camel@laptop>
Date:	Wed, 17 Aug 2011 23:47:59 +0200
From:	Peter Zijlstra <a.p.zijlstra@...llo.nl>
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	"Luck, Tony" <tony.luck@...el.com>, linux-kernel@...r.kernel.org,
	Don Zickus <dzickus@...hat.com>,
	Matthew Garrett <mjg@...hat.com>, Ingo Molnar <mingo@...e.hu>,
	Thomas Gleixner <tglx@...utronix.de>
Subject: Re: pstore: change mutex locking to spin_locks

On Wed, 2011-08-17 at 14:22 -0700, Andrew Morton wrote:
> It's still bad if lockdep is enabled.  See
> kernel/lockdep.c:lock_acquire() and lock_release().  They aren't
> NMI-safe. 

Good thing nmi_enter() does lockdep_disable() and makes lock_acquire()
bail on if (current->lockdep_recursion).

Still the fact that pstore needs locks from NMI context (let alone tried
to use a mutex) makes one think one should avoid it like the plague.

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