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From: Andi Kleen <andi@firstfloor.org>
To: John Stultz <john.stultz@linaro.org>
Cc: lkml <linux-kernel@vger.kernel.org>,
	John Stultz <johnstul@us.ibm.com>,
	Paul Mackerras <paulus@samba.org>,
	"Paul E. McKenney" <paulmck@linux.vnet.ibm.com>,
	Anton Blanchard <anton@samba.org>,
	Thomas Gleixner <tglx@linutronix.de>
Subject: Re: [PATCH] time: Add locking to xtime access in get_seconds()
Date: Tue, 03 May 2011 20:52:46 -0700	[thread overview]
Message-ID: <m2oc3jxgtt.fsf@firstfloor.org> (raw)
In-Reply-To: <1304478708-1273-1-git-send-email-john.stultz@linaro.org> (John Stultz's message of "Tue, 3 May 2011 20:11:48 -0700")

John Stultz <john.stultz@linaro.org> writes:

> From: John Stultz <johnstul@us.ibm.com>
>
> So get_seconds() has always been lock free, with the assumption
> that accessing a long will be atomic.
>
> However, recently I came across an odd bug where time() access could
> occasionally be inconsistent, but only on power7 hardware. The

Shouldn't a single rmb() be enough to avoid that?

If not then I suspect there's a lot more code buggy on that CPU than
just the time.

-Andi

-- 
ak@linux.intel.com -- Speaking for myself only

  reply	other threads:[~2011-05-04  3:52 UTC|newest]

Thread overview: 50+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2011-05-04  3:11 [PATCH] time: Add locking to xtime access in get_seconds() John Stultz
2011-05-04  3:52 ` Andi Kleen [this message]
2011-05-05  2:54   ` john stultz
2011-05-05  5:44     ` Eric Dumazet
2011-05-05  6:21       ` john stultz
2011-05-05  6:50         ` Eric Dumazet
2011-05-05  8:14         ` Paul E. McKenney
2011-05-05 18:51           ` john stultz
2011-05-05 14:04         ` [RFC] time: xtime_lock is held too long Eric Dumazet
2011-05-05 14:39           ` Thomas Gleixner
2011-05-05 15:08             ` Eric Dumazet
2011-05-05 15:59               ` Thomas Gleixner
2011-05-05 21:01                 ` Andi Kleen
2011-05-06  1:41                   ` Eric Dumazet
2011-05-06  6:55                     ` Andi Kleen
2011-05-06 10:18                   ` Thomas Gleixner
2011-05-06 10:22                     ` Ingo Molnar
2011-05-06 16:53                       ` Andi Kleen
2011-05-07  8:20                         ` Ingo Molnar
2011-05-06 16:59                     ` Andi Kleen
2011-05-06 17:09                       ` Eric Dumazet
2011-05-06 17:17                         ` Andi Kleen
2011-05-06 17:42                       ` Eric Dumazet
2011-05-06 17:50                         ` Andi Kleen
2011-05-06 19:26                           ` Eric Dumazet
2011-05-06 20:04                             ` Eric Dumazet
2011-05-06 20:24                               ` john stultz
2011-05-06 22:30                                 ` Eric Dumazet
2011-05-06 22:46                                   ` john stultz
2011-05-06 23:00                                     ` Eric Dumazet
2011-05-06 23:28                                       ` john stultz
2011-05-07  5:02                                         ` Eric Dumazet
2011-05-07  7:11                                           ` Henrik Rydberg
2011-05-09  8:40                                         ` Thomas Gleixner
2011-05-12  9:13                                         ` [PATCH] seqlock: don't smp_rmb in seqlock reader spin loop, [PATCH] seqlock: don't smp_rmb in seqlock reader spin loop Milton Miller
2011-05-12  9:13                                           ` Milton Miller
2011-05-12  9:35                                           ` Eric Dumazet
2011-05-12  9:35                                             ` Eric Dumazet
2011-05-12 14:08                                           ` Andi Kleen
2011-05-12 14:08                                             ` Andi Kleen
2011-05-06 20:18                         ` [RFC] time: xtime_lock is held too long john stultz
2011-05-05 17:57     ` [PATCH] time: Add locking to xtime access in get_seconds() Andi Kleen
2011-05-05 20:17       ` john stultz
2011-05-05 20:24         ` Eric Dumazet
2011-05-05 20:40           ` john stultz
2011-05-05 20:43             ` Eric Dumazet
2011-05-05 20:56         ` Andi Kleen
2011-05-04 16:51 ` Max Asbock
2011-05-04 21:05   ` Andi Kleen
2011-05-04 23:05   ` john stultz

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