linux-kernel - Re: [PATCH 1/3] posix-timers: remove idr

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Date:	Fri, 10 Jun 2011 22:44:28 +0200
From:	Andi Kleen <andi@...stfloor.org>
To:	Eric Dumazet <eric.dumazet@...il.com>
Cc:	Andi Kleen <andi@...stfloor.org>, linux-kernel@...r.kernel.org,
	tglx@...utronix.de, Andi Kleen <ak@...ux.intel.com>
Subject: Re: [PATCH 1/3] posix-timers: remove idr_lock

On Fri, Jun 10, 2011 at 10:40:38PM +0200, Eric Dumazet wrote:
> Le vendredi 10 juin 2011 à 13:13 -0700, Andi Kleen a écrit :
> > From: Andi Kleen <ak@...ux.intel.com>
> > 
> > idr_lock is only used to protect the global posix_timers idr,
> > but idr does its own locking (or RCUing) anyways and doesn't
> > need it. So remove it.
> 
> Are you sure of this assertion Andi ?
> 
> I believe we need an external synchronization before calling
> idr_remove() / idr_get_new()

idr has its own lock and from a quick check it seemed to always
take it when needed. Also ipc/* don't take a lock for this as far
as I can see, and I think RCU idr was designed for that.

-Andi
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