From: Christian Franke <Christian.Franke@t-online.de>
To: cygwin@cygwin.com
Subject: Re: clock_getres(CLOCK_REALTIME, .) may return an outdated and too high resolution
Date: Tue, 27 Mar 2012 19:00:00 -0000 [thread overview]
Message-ID: <4F720E19.5000809@t-online.de> (raw)
In-Reply-To: <20120327182823.GV30721@calimero.vinschen.de>
Corinna Vinschen wrote:
> On Mar 27 20:01, Christian Franke wrote:
>> Corinna Vinschen wrote:
>>> On Mar 26 19:00, Christian Franke wrote:
>>>> Corinna Vinschen wrote:
>>>>> I see your point, but what bugs me a bit is the fact that
>>>>> clock_getres(CLOCK_REALTIME) and clock_setres(CLOCK_REALTIME) will
>>>>> always return the same value coarsest, regardless what value has been set.
>>>> If clock_setres was called and succeeded, then clock_getres(.)
>>>> should return the value set before.
>>>>
>>>> If clock_setres was not called, the coarsest value is IMO the only
>>>> value that can be guaranteed.
>>>>
>>>> The actual value returned by NtQueryTimerResolution is simply
>>>> useless in this context: It is the minimum of all resolutions
>>>> currently set by all running processes. It may change at any time.
>>>> There is apparently no way the query the current setting of the
>>>> current process.
>>> Uh, right, I misunderstood. I reverted the change to clock_setres.
>> Sorry, I probably forgot to mention that NtSetTimerResolution
>> returns the same useless actual value than NtQueryTimerResolution.
>>
>> I would suggest:
>>
>> status = NtSetTimerResolution (period, TRUE,&actual);
>> if (!NT_SUCCESS (status))
>> { ... return -1; }
>> - minperiod = actual;
>> + minperiod = period;
> But that's not right. The "actual" value is not useless, but the value
> the resolution has actually been set to.
No, again this is the minimum of all resolutions currently set by all
processes.
> The OS just doesn't support
> arbitrary values for the period.
>
Yes - but in 'actual' a smaller value than the value set for the current
process may be returned.
Christian
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next prev parent reply other threads:[~2012-03-27 19:00 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-03-21 23:00 Christian Franke
2012-03-22 9:34 ` Corinna Vinschen
2012-03-22 9:39 ` Peter Rosin
2012-03-22 9:50 ` Corinna Vinschen
2012-03-22 17:47 ` Christian Franke
2012-03-26 8:52 ` Corinna Vinschen
2012-03-26 17:01 ` Christian Franke
2012-03-27 9:11 ` Corinna Vinschen
2012-03-27 18:02 ` Christian Franke
2012-03-27 18:29 ` Corinna Vinschen
2012-03-27 19:00 ` Christian Franke [this message]
2012-03-27 20:51 ` Corinna Vinschen
2012-03-27 21:29 ` Christian Franke
2012-03-28 7:40 ` Corinna Vinschen
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