From mboxrd@z Thu Jan  1 00:00:00 1970
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	<99a6e3a7cd4a1a6da9d06b97ddff4e37@gmx.de>
Date: Sun, 22 Mar 2009 21:04:54 -0700
Message-ID: <13426df10903222104m424280d7ub9503f035eb708cb@mail.gmail.com>
From: ron minnich <rminnich@gmail.com>
To: Fans of the OS Plan 9 from Bell Labs <9fans@9fans.net>
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Subject: Re: [9fans] fossil periodic thread does zero sleep()
Topicbox-Message-UUID: c210f0e6-ead4-11e9-9d60-3106f5b1d025

This is from mobile so I can not look at code much but if you are
converting nanoseconds to milliseconds you multiply by 1e6 not 1e-6 I
think.

Ron

On 3/22/09, cinap_lenrek@gmx.de <cinap_lenrek@gmx.de> wrote:
> This is actualy very interesting. Riped the parts from periodic.c
> to play a with the code to see how it reacts to some changes.
>
> The code below reproduces the problem:
>
> sleep()+0x7 /sys/src/libc/9syscall/sleep.s:5
> periodicThread(msec=0x3e8)+0xb2 /tmp/a.c:21
> 	ct=0x47a68e5b
> 	t=0x47e50e4d
> 	ts=0x0
> main()+0x10 /tmp/a.c:32
> _main+0x31 /sys/src/libc/386/main9.s:16
>
>
> The zerosleeps go away if one uncomments the foo print. It also
> goes away if one makes the sleep one milli second longer by
> changing ts to ts+1.
>
> I would love if anybody gives a good explaination of this bug
> and how to fix it :-)
>
> #include <u.h>
> #include <libc.h>
>
> static void
> periodicThread(int msec)
> {
> 	double t, ct, ts;
>
> 	ct = nsec()*1e-6;
> 	t = ct + msec;
>
> 	for(;;){
> 		/* skip missed */
> 		while(t <= ct)
> 			t += msec;
>
> 		ts = t - ct;
> 		if(ts > 1000)
> 			ts = 1000;
> 		sleep(ts);
> 		ct = nsec()*1e-6;
> 		if(t <= ct){
> //			print("foo!\n");
> 			t += msec;
> 		}
> 	}
> }
>
> void
> main(int argc, char *argv[])
> {
> 	periodicThread(1000);
> }
>

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