From: David Mosberger <davidm@napali.hpl.hp.com>
To: linux-ia64@vger.kernel.org
Subject: [Linux-ia64] Re: [PATCH] settimeofday() not synchronised with gettimeofday()
Date: Thu, 13 Mar 2003 20:03:02 +0000 [thread overview]
Message-ID: <marc-linux-ia64-105590709806082@msgid-missing> (raw)
>>>>> On Thu, 13 Mar 2003 17:53:43 +0100, Eric Piel <Eric.Piel@Bull.Net> said:
Eric> gettimeofday() gave a time BEFORE the time we set! First,
Eric> I've corrected an obvious problem due to the change of the
Eric> returned value of gettimeoffset() from usec to nsec in
Eric> settimeofday().
Ah, yes, thanks for catching that.
Eric> David, I think you can apply it, at least :-)
The patch looks mostly OK, but it compares an "unsigned long" for < 0,
which can't be right. I can fix that, though (I'll also fix the
comment for gettimeoffset()).
Eric> However, now, it still gives negative difference: # ./a.out
Eric> requested: 1047572128s 2564ns new: 1047572128s 1588ns diff is
Eric> -0.000976000sec
Eric> That's better but there is still something... Can anyone
Eric> reproduce this bug? Any idea about what may cause this shifted
Eric> results?
Are you running ntp?
On a related topic: there is another strange 2.5 time related bug. On
2.4:
$ time sleep 16.02
real 0m16.027s
user 0m0.002s
sys 0m0.001s
On 2.5:
$ time sleep 16
real 0m16.002s
user 0m0.001s
sys 0m0.002s
$ time sleep 16.02
real 0m25.189s
user 0m0.000s
sys 0m0.001s
So clearly something very strange is going on. My suspicion is that
the bug was introduced back when x86 switched from 100Hz to 1000Hz
ticks, but that's just a guess. Eric, would you be
able/willing/interested to look into this?
--david
reply other threads:[~2003-03-13 20:03 UTC|newest]
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