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Message-ID: <1386209910.30495.146.camel@edumazet-glaptop2.roam.corp.google.com>
Subject: Re: lots of brief rcu stalls.
From: Eric Dumazet <eric.dumazet@gmail.com>
To: paulmck@linux.vnet.ibm.com
Cc: Dave Jones <davej@redhat.com>, Linux Kernel <linux-kernel@vger.kernel.org>
Date: Wed, 04 Dec 2013 18:18:30 -0800
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References: <20131204232838.GA25592@redhat.com>
	 <20131205001614.GI15492@linux.vnet.ibm.com>
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On Wed, 2013-12-04 at 16:16 -0800, Paul E. McKenney wrote:
> +	if (rdp->rsp == rcu_state &&
> +	    ULONG_CMP_GE(ACCESS_ONCE(jiffies), rdp->rsp->jiffies_resched)) {
> +		rdp->rsp->jiffies_resched += 5;
> +		resched_cpu(rdp->cpu);
> +	}
> +
>  	return 0;
>  }

jiffies should not need ACCESS_ONCE(), right ?

It is one of the few variables marked with volatile keyword.