Date: Fri, 21 Jan 2000 00:07:45 -0800 (PST) From: davids@webmaster.com To: FreeBSD-gnats-submit@freebsd.org Subject: misc/16245: libc_r bug in poll, timeout math suspicious Message-ID: <200001210807.AAA14016@tock.gpsclock.com>
next in thread | raw e-mail | index | archive | help
>Number: 16245
>Category: misc
>Synopsis: poll misconverts milliseconds to nanoseconds
>Confidential: no
>Severity: serious
>Priority: medium
>Responsible: freebsd-bugs
>State: open
>Quarter:
>Keywords:
>Date-Required:
>Class: sw-bug
>Submitter-Id: current-users
>Arrival-Date: Fri Jan 21 00:10:01 PST 2000
>Closed-Date:
>Last-Modified:
>Originator: David Schwartz
>Release: FreeBSD 3.3-STABLE i386
>Organization:
Webmaster, Incorporated
>Environment:
FreeBSD 3.3-STALE system. Using libc_r with loops based heavily
around poll with timeouts.
>Description:
Threaded code that uses libc_r and is based around 'poll' uses much
more system CPU time than it should. Problem is tracked to a math error in
the 'poll' routine.
>How-To-Repeat:
Run any program that calls poll in a tight loop, relying on the
timeout in 'poll' to prevent a spin.
>Fix:
In libc_r/uthread/uthread_poll.c, we find the following suspicious
math:
} else if (timeout > 0) {
/* Convert the timeout in msec to a timespec: */
ts.tv_sec = timeout / 1000;
ts.tv_nsec = (timeout % 1000) * 1000;
/* Set the wake up time: */
_thread_kern_set_timeout(&ts);
} else if (timeout < 0) {
This conversion from milliseconds to nanoseconds is incorrect. There
are a million milliseconds in a nanosecond.
>Release-Note:
>Audit-Trail:
>Unformatted:
To Unsubscribe: send mail to majordomo@FreeBSD.org
with "unsubscribe freebsd-bugs" in the body of the message
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?200001210807.AAA14016>