From: Joe Perches <joe@perches.com>
To: Eric Dumazet <eric.dumazet@gmail.com>
Cc: paulmck@linux.vnet.ibm.com, Dave Jones <davej@redhat.com>,
Linux Kernel <linux-kernel@vger.kernel.org>,
Josh Triplett <josh@freedesktop.org>,
Ingo Molnar <mingo@redhat.com>,
Peter Zijlstra <peterz@infradead.org>
Subject: Re: lots of brief rcu stalls.
Date: Wed, 04 Dec 2013 18:36:05 -0800 [thread overview]
Message-ID: <1386210965.30493.84.camel@joe-AO722> (raw)
In-Reply-To: <1386209910.30495.146.camel@edumazet-glaptop2.roam.corp.google.com>
On Wed, 2013-12-04 at 18:18 -0800, Eric Dumazet wrote:
> On Wed, 2013-12-04 at 16:16 -0800, Paul E. McKenney wrote:
> > + ULONG_CMP_GE(ACCESS_ONCE(jiffies), rdp->rsp->jiffies_resched)) {
perhaps time_before_eq
> jiffies should not need ACCESS_ONCE(), right ?
>
> It is one of the few variables marked with volatile keyword.
It does seem redundant
$ git grep -n "ACCESS_ONCE(jiffies)"
kernel/rcu/torture.c:1354: jiffies_snap = ACCESS_ONCE(jiffies);
kernel/rcu/torture.c:1363: jiffies_snap = ACCESS_ONCE(jiffies);
kernel/rcu/tree.c:820: unsigned long j = ACCESS_ONCE(jiffies);
kernel/rcu/tree.c:975: j = ACCESS_ONCE(jiffies);
kernel/sched/core.c:2324: unsigned long next, now = ACCESS_ONCE(jiffies);
kernel/sched/proc.c:536: unsigned long curr_jiffies = ACCESS_ONCE(jiffies);
kernel/sched/proc.c:558: unsigned long curr_jiffies = ACCESS_ONCE(jiffies);
next prev parent reply other threads:[~2013-12-05 2:36 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-12-04 23:28 Dave Jones
2013-12-05 0:16 ` Paul E. McKenney
2013-12-05 1:22 ` Dave Jones
2013-12-05 2:44 ` Paul E. McKenney
2013-12-05 16:49 ` Paul E. McKenney
2013-12-05 17:15 ` Dave Jones
2013-12-05 17:31 ` Paul E. McKenney
2013-12-05 2:18 ` Eric Dumazet
2013-12-05 2:36 ` Joe Perches [this message]
2013-12-05 2:51 ` Paul E. McKenney
2013-12-05 2:43 ` Paul E. McKenney
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