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Date: Mon, 23 Mar 2009 06:27:14 -0700
Message-ID: <13426df10903230627p2d9845b8xc6c3937b78f09421@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()
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Sigh ... Do not send mail when tired. Was thinking of different problem.

Ron

On 3/22/09, ron minnich <rminnich@gmail.com> wrote:
> 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);
>> }
>>
>
> --
> Sent from my mobile device
>

--
Sent from my mobile device