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Date:	Sun, 29 Sep 2013 17:51:53 -0700
From:	Linus Torvalds <>
To:	Davidlohr Bueso <>
Cc:	Ingo Molnar <>, Waiman Long <>,
	Ingo Molnar <>,
	Andrew Morton <>,
	Linux Kernel Mailing List <>,
	Rik van Riel <>,
	Peter Hurley <>,
	Davidlohr Bueso <>,
	Alex Shi <>,
	Tim Chen <>,
	Peter Zijlstra <>,
	Andrea Arcangeli <>,
	Matthew R Wilcox <>,
	Dave Hansen <>,
	Michel Lespinasse <>,
	Andi Kleen <>,
	"Chandramouleeswaran, Aswin" <>,
	"Norton, Scott J" <>
Subject: Re: [PATCH] rwsem: reduce spinlock contention in wakeup code path

On Sun, Sep 29, 2013 at 5:40 PM, Davidlohr Bueso <> wrote:
> Hmm, I'm getting the following at bootup:
>  May be due to missing lock nesting notation

Yes it is. And that reminds me of a problem I think we had with this
code: we had a possible case of the preemption counter nesting too
deeply. I forget the details, but it was something people worried

That mm_take_all_locks() thing is really special, and I suspect that
if we go down this way we should just do a single preempt-disable and
then use the arch_write_lock() to avoid both the lockdep splat _and_
the preemption counter overflow.

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