From: cinap_lenrek@gmx.de
To: 9fans@9fans.net
Subject: Re: [9fans] fossil periodic thread does zero sleep()
Date: Mon, 23 Mar 2009 01:16:07 +0100 [thread overview]
Message-ID: <99a6e3a7cd4a1a6da9d06b97ddff4e37@gmx.de> (raw)
In-Reply-To: <959ad71b3d677ea98c0e6b2ef28db2dd@quanstro.net>
[-- Attachment #1: Type: text/plain, Size: 1037 bytes --]
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);
}
[-- Attachment #2: Type: message/rfc822, Size: 2176 bytes --]
From: erik quanstrom <quanstro@quanstro.net>
To: 9fans@9fans.net
Subject: Re: [9fans] fossil periodic thread does zero sleep()
Date: Sun, 22 Mar 2009 19:41:24 -0400
Message-ID: <959ad71b3d677ea98c0e6b2ef28db2dd@quanstro.net>
> Can anybody explain this fossil behaviour from the periodic code?
what if 0 < t - ct < 1?
wouldn't it be a good idea to replace the doubles with vlongs?
and replace *1e-6 with /1000000? that would make 0 < t - ct < 1
impossible.
- erik
next prev parent reply other threads:[~2009-03-23 0:16 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2009-03-22 23:13 cinap_lenrek
2009-03-22 23:41 ` erik quanstrom
2009-03-23 0:16 ` cinap_lenrek [this message]
2009-03-23 0:24 ` erik quanstrom
2009-03-23 0:52 ` cinap_lenrek
2009-03-23 0:54 ` erik quanstrom
2009-03-23 4:04 ` ron minnich
2009-03-23 13:27 ` ron minnich
2009-03-23 0:24 ` cinap_lenrek
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=99a6e3a7cd4a1a6da9d06b97ddff4e37@gmx.de \
--to=cinap_lenrek@gmx.de \
--cc=9fans@9fans.net \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).