linux-kernel - Re: [PATCH RFC tip/core/rcu 24/28] rcu: Introduce bulk reference count

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Date:	Mon, 28 Nov 2011 19:35:27 +0100
From:	Peter Zijlstra <peterz@...radead.org>
To:	paulmck@...ux.vnet.ibm.com
Cc:	linux-kernel@...r.kernel.org, mingo@...e.hu, laijs@...fujitsu.com,
	dipankar@...ibm.com, akpm@...ux-foundation.org,
	mathieu.desnoyers@...ymtl.ca, josh@...htriplett.org,
	niv@...ibm.com, tglx@...utronix.de, rostedt@...dmis.org,
	Valdis.Kletnieks@...edu, dhowells@...hat.com,
	eric.dumazet@...il.com, darren@...art.com, patches@...aro.org
Subject: Re: [PATCH RFC tip/core/rcu 24/28] rcu: Introduce bulk reference
 count

On Mon, 2011-11-28 at 10:31 -0800, Paul E. McKenney wrote:
> >   local_irq_save(flags);
> >   srcu_read_lock(&my_srcu_domain);
> >   local_irq_restore(flags);
> > 
> > and
> > 
> >   local_irq_save(flags);
> >   srcu_read_unlock(&my_srcu_domain);
> >   local_irq_restore(flags)
> > 
> > Doesn't look to be too hard, or confusing.
> 
> Ah, OK, I was under the mistaken impression that lockdep would splat
> if you did (for example) srcu_read_lock() in an exception handler and
> srcu_read_unlock() in the context of the task that took the exception. 

I don't think it will, lockdep does very little actual validation on the
RCU locks other than recording they're held. But if they do, the planned
TODO item will get inversed.

Should be easy enough to test I guess.
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