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From: john stultz <johnstul@us.ibm.com>
To: Max Asbock <masbock@linux.vnet.ibm.com>
Cc: lkml <linux-kernel@vger.kernel.org>,
	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: Wed, 04 May 2011 16:05:58 -0700	[thread overview]
Message-ID: <1304550358.2943.10.camel@work-vm> (raw)
In-Reply-To: <1304527860.21305.5.camel@w-amax.beaverton.ibm.com>

On Wed, 2011-05-04 at 09:51 -0700, Max Asbock wrote:
> On Tue, 2011-05-03 at 20:11 -0700, John Stultz wrote:
> > 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.
> > 
> 
> get_seconds() is used in the x86 machine check handler and there is a
> comment saying:
> /* We hope get_seconds stays lockless */
> 
> This needs to be carefully looked at if locking is introduced to
> get_seconds().

Ah. Thanks for pointing this out Max.

I'll go ahead and use Andi's suggestion of the rmb();

Patch soon to follow.

thanks
-john



      parent reply	other threads:[~2011-05-04 23:06 UTC|newest]

Thread overview: 47+ 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
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  9:35                                             ` Eric Dumazet
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 [this message]

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