From: Thomas Gleixner <tglx@linutronix.de>
To: Karsten Wiese <fzu@wemgehoertderstaat.de>
Cc: John Stultz <johnstul@us.ibm.com>, Tim Ricketts <tr@earth.li>,
Michael Smith <msmith@xiph.org>,
LKML <linux-kernel@vger.kernel.org>,
Andy Wingo <wingo@fluendo.com>, Ingo Molnar <mingo@elte.hu>
Subject: Re: gettimeofday() jumping into the future
Date: Thu, 3 Apr 2008 08:28:25 +0200 (CEST) [thread overview]
Message-ID: <alpine.LFD.1.10.0804030827180.3219@apollo.tec.linutronix.de> (raw)
In-Reply-To: <200804030157.32086.fzu@wemgehoertderstaat.de>
On Thu, 3 Apr 2008, Karsten Wiese wrote:
> > To prevent this TSC specific wreckage we need to compare the TSC value
> > against the reference value and return the latter when it is larger
> > than the actual TSC value.
>
> Last paragraph IMO should be:
> To prevent this TSC specific wreckage we need to substract the
> reference value from the TSC value, interpret the result as
> signed. If the interpreted result is negative, return the reference
> value, else the TSC Value.
> Your patch misses the corner case where TSC value is < reference _and_ valid
> at TSC wrap around.
In about 200 years on a 3Ghz box.
> The access to the reference value needs a (the xtime ?) lock on 32bit, no?
The readout is under xtime lock anyway.
Thanks,
tglx
next prev parent reply other threads:[~2008-04-03 6:29 UTC|newest]
Thread overview: 23+ messages / expand[flat|nested] mbox.gz Atom feed top
2007-08-23 11:08 Michael Smith
2007-08-23 11:36 ` Gerald Britton
2007-08-23 13:03 ` Avi Kivity
2007-08-23 20:09 ` H. Peter Anvin
2007-08-23 20:07 ` H. Peter Anvin
2007-08-23 11:47 ` Peter Zijlstra
2007-08-23 12:20 ` Michael Smith
2007-08-23 18:47 ` john stultz
2007-08-25 16:44 ` Michael Smith
2008-03-30 21:17 ` Tim Ricketts
2008-03-31 7:18 ` Andi Kleen
2008-04-03 11:47 ` James Courtier-Dutton
2008-04-03 12:22 ` James Courtier-Dutton
2008-04-03 12:44 ` James Courtier-Dutton
2008-04-11 23:11 ` john stultz
2008-03-31 8:55 ` Thomas Gleixner
2008-03-31 16:03 ` John Stultz
2008-04-02 11:22 ` Thomas Gleixner
2008-04-02 23:57 ` Karsten Wiese
2008-04-03 6:28 ` Thomas Gleixner [this message]
2008-04-02 4:26 ` Mihai Donțu
2008-04-02 4:27 ` Mihai Donțu
[not found] <47F3F313.7030803@vmware.com>
2008-04-02 22:40 ` Tim Mann
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