Date: 13 Oct 2001 22:56:59 -0000 From: root@do-labs.spb.ru To: FreeBSD-gnats-submit@freebsd.org Subject: kern/31255: select with zero timeout returns 0 even when data pending Message-ID: <20011013225659.7152.qmail@do-labs.spb.ru>
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>Number: 31255
>Category: kern
>Synopsis: select with zero timeout returns 0 even when data pending
>Confidential: no
>Severity: non-critical
>Priority: low
>Responsible: freebsd-bugs
>State: open
>Quarter:
>Keywords:
>Date-Required:
>Class: sw-bug
>Submitter-Id: current-users
>Arrival-Date: Sat Oct 13 12:00:06 PDT 2001
>Closed-Date:
>Last-Modified:
>Originator: dozen@osw.com.ru
>Release: FreeBSD 4.3-RELEASE-p20 i386
>Organization:
>Environment:
System: FreeBSD eix.do-labs.spb.ru 4.3-RELEASE-p20 FreeBSD 4.3-RELEASE-p20 #1: Fri Oct 12 22:18:27 GMT 2001 root@eix.do-labs.spb.ru:/usr/src/sys/compile/EIX i386
>Description:
struct timeval tv = { 0,0 };
rc = select(...,&tv);
This code will always return zero even if data is pending
one any descriptor or any descriptor is ready to write.
This is because check for timed out performed before
asking kernel about descriptor state.
Single Unix Spec do not states exactly that zero timeout shall
lead to immediate return with correct descriptor number as result,
but it looks like it is supposed to be as such.
>How-To-Repeat:
>Fix:
The problem code is in /usr/src/sys/kern/sys_generic.c
>Release-Note:
>Audit-Trail:
>Unformatted:
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