linux-kernel - Re: [PATCH 1/3] sched, timer: Remove usages of ACCESS

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Date:	Tue, 14 Apr 2015 19:59:06 -0400
From:	Steven Rostedt <rostedt@...dmis.org>
To:	Jason Low <jason.low2@...com>
Cc:	Linus Torvalds <torvalds@...ux-foundation.org>,
	Peter Zijlstra <peterz@...radead.org>,
	Ingo Molnar <mingo@...nel.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	linux-kernel@...r.kernel.org,
	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Oleg Nesterov <oleg@...hat.com>,
	Mike Galbraith <umgwanakikbuti@...il.com>,
	Frederic Weisbecker <fweisbec@...il.com>,
	Mel Gorman <mgorman@...e.de>,
	Preeti U Murthy <preeti@...ux.vnet.ibm.com>,
	hideaki.kimura@...com, Aswin Chandramouleeswaran <aswin@...com>,
	Scott J Norton <scott.norton@...com>
Subject: Re: [PATCH 1/3] sched, timer: Remove usages of ACCESS_ONCE in the
 scheduler

On Tue, 14 Apr 2015 16:09:44 -0700
Jason Low <jason.low2@...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?

>  	p->mm->numa_scan_offset = 0;
>  }
>  

-- Steve
--
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