linux-kernel - Re: [PATCH v2 1/2] sched: Add cond_resched_rcu

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Message-ID: <20130504180315.GB3659@linux.vnet.ibm.com>
Date:	Sat, 4 May 2013 11:03:16 -0700
From:	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
To:	Julian Anastasov <ja@....bg>
Cc:	Peter Zijlstra <peterz@...radead.org>,
	Simon Horman <horms@...ge.net.au>,
	Eric Dumazet <eric.dumazet@...il.com>,
	Ingo Molnar <mingo@...hat.com>, lvs-devel@...r.kernel.org,
	netdev@...r.kernel.org, netfilter-devel@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	Pablo Neira Ayuso <pablo@...filter.org>,
	Dipankar Sarma <dipankar@...ibm.com>
Subject: Re: [PATCH v2 1/2] sched: Add cond_resched_rcu_lock() helper

On Sat, May 04, 2013 at 10:23:31AM +0300, Julian Anastasov wrote:
> 
> 	Hello,
> 
> On Fri, 3 May 2013, Paul E. McKenney wrote:
> 
> > static inline int cond_resched_rcu(void)
> > {
> > #if defined(CONFIG_DEBUG_ATOMIC_SLEEP) || !defined(CONFIG_PREEMPT_RCU)
> > 	rcu_read_unlock();
> > 	cond_resched();
> > 	rcu_read_lock();
> > #endif
> > }
> > 
> > This adds absolutely no overhead in non-debug builds of CONFIG_PREEMPT_RCU,
> > does the checking in debug builds, and allows voluntary preemption in
> > !CONFIG_PREEMPT_RCU builds.  CONFIG_PROVE_RCU builds will check for an
> > (illegal) outer rcu_read_lock() in CONFIG_PREEMPT_RCU builds, and you
> > will get "scheduling while atomic" in response to an outer rcu_read_lock()
> > in !CONFIG_PREEMPT_RCU builds.
> > 
> > It also seems to me a lot simpler.
> > 
> > Does this work, or am I still missing something?
> 
> 	Works perfectly. Thanks! Tested CONFIG_PREEMPT_RCU=y/n,
> the errors messages with extra RCU lock.

Very good!  Please send the patch along, and I will ack it.

						Thanx, Paul

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