From: Jason Low <jason.low2@hp.com>
To: Steven Rostedt <rostedt@goodmis.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>,
Peter Zijlstra <peterz@infradead.org>,
Ingo Molnar <mingo@kernel.org>,
Thomas Gleixner <tglx@linutronix.de>,
linux-kernel@vger.kernel.org,
"Paul E. McKenney" <paulmck@linux.vnet.ibm.com>,
Andrew Morton <akpm@linux-foundation.org>,
Oleg Nesterov <oleg@redhat.com>,
Mike Galbraith <umgwanakikbuti@gmail.com>,
Frederic Weisbecker <fweisbec@gmail.com>,
Mel Gorman <mgorman@suse.de>,
Preeti U Murthy <preeti@linux.vnet.ibm.com>,
hideaki.kimura@hp.com, Aswin Chandramouleeswaran <aswin@hp.com>,
Scott J Norton <scott.norton@hp.com>,
jason.low2@hp.com
Subject: Re: [PATCH 1/3] sched, timer: Remove usages of ACCESS_ONCE in the scheduler
Date: Tue, 14 Apr 2015 19:12:33 -0700 [thread overview]
Message-ID: <1429063953.7039.88.camel@j-VirtualBox> (raw)
In-Reply-To: <20150414195906.3adc89d9@gandalf.local.home>
Hi Steven,
On Tue, 2015-04-14 at 19:59 -0400, Steven Rostedt wrote:
> On Tue, 14 Apr 2015 16:09:44 -0700
> Jason Low <jason.low2@hp.com> wrote:
>
>
> > @@ -2088,7 +2088,7 @@ void task_numa_fault(int last_cpupid, int mem_node, int pages, int flags)
> >
> > static void reset_ptenuma_scan(struct task_struct *p)
> > {
> > - ACCESS_ONCE(p->mm->numa_scan_seq)++;
> > + WRITE_ONCE(p->mm->numa_scan_seq, READ_ONCE(p->mm->numa_scan_seq) + 1);
>
> Is the READ_ONCE() inside the WRITE_ONCE() really necessary?
Yeah, I think so to be safe, otherwise, the access of
p->mm->numa_scan_seq in the 2nd parameter doesn't have the volatile
cast.
next prev parent reply other threads:[~2015-04-15 2:12 UTC|newest]
Thread overview: 34+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-04-14 23:09 [PATCH 0/3] sched, timer: Improve scalability of itimers Jason Low
2015-04-14 23:09 ` [PATCH 1/3] sched, timer: Remove usages of ACCESS_ONCE in the scheduler Jason Low
2015-04-14 23:59 ` Steven Rostedt
2015-04-15 2:12 ` Jason Low [this message]
2015-04-15 2:40 ` Steven Rostedt
2015-04-15 7:46 ` Ingo Molnar
2015-04-15 18:49 ` Jason Low
2015-04-15 19:16 ` Steven Rostedt
2015-04-16 2:46 ` Jason Low
2015-04-16 16:52 ` Peter Zijlstra
2015-04-16 18:02 ` Ingo Molnar
2015-04-16 18:15 ` Peter Zijlstra
2015-04-16 18:24 ` Ingo Molnar
2015-04-16 19:02 ` Peter Zijlstra
2015-04-16 19:41 ` Paul E. McKenney
2015-04-17 3:25 ` Jason Low
2015-04-17 8:19 ` Ingo Molnar
2015-04-16 21:00 ` Jason Low
2015-04-16 2:29 ` Jason Low
2015-04-16 2:37 ` Steven Rostedt
2015-04-14 23:09 ` [PATCH 2/3] sched, timer: Use atomics for thread_group_cputimer to improve scalability Jason Low
2015-04-15 7:33 ` Ingo Molnar
2015-04-15 7:35 ` Ingo Molnar
2015-04-15 17:14 ` Jason Low
2015-04-15 10:37 ` Preeti U Murthy
2015-04-15 19:09 ` Jason Low
2015-04-15 13:25 ` Frederic Weisbecker
2015-04-15 13:32 ` Peter Zijlstra
2015-04-15 20:04 ` Jason Low
2015-04-15 14:23 ` Davidlohr Bueso
2015-04-15 21:15 ` Jason Low
2015-04-14 23:09 ` [PATCH 3/3] sched, timer: Use cmpxchg to do updates in update_gt_cputime() Jason Low
2015-04-14 23:53 ` [PATCH 0/3] sched, timer: Improve scalability of itimers Linus Torvalds
2015-04-15 7:24 ` Ingo Molnar
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