Date: 17 Sep 2002 16:13:34 -0000 From: Karl Lehenbauer <karl@habitat.procplace.com> To: FreeBSD-gnats-submit@FreeBSD.org Subject: kern/42875: gettimeofday super rarely returns an impossible tv_usec value Message-ID: <20020917161334.20862.qmail@habitat.procplace.com>
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>Number: 42875
>Category: kern
>Synopsis: gettimeofday super rarely returns an impossible tv_usec value
>Confidential: no
>Severity: serious
>Priority: high
>Responsible: freebsd-bugs
>State: open
>Quarter:
>Keywords:
>Date-Required:
>Class: sw-bug
>Submitter-Id: current-users
>Arrival-Date: Tue Sep 17 09:20:01 PDT 2002
>Closed-Date:
>Last-Modified:
>Originator: Karl Lehenbauer
>Release: FreeBSD 4.6-STABLE i386
>Organization:
Procplace.com, Inc.
>Environment:
System: FreeBSD habitat.procplace.com 4.6-STABLE FreeBSD 4.6-STABLE #3: Mon Aug 5 22:36:39 CDT 2002 dbaker@habitat.procplace.com:/usr/local/dbakerspawn/builds/obj/RELENG_4/usr/local/dbakerspawn/RELENG/4/src/sys/2UIAHPROCPLACE i386
>Description:
Maybe one in thirty million times, gettimeofday will return
an invalid tv_usec value (microseconds). It should ALWAYS
be between 0 and 999999, but it is occasionally a very large
negative number.
>How-To-Repeat:
Compile this program and let it run for a super long time.
Preferably use a machine that is actually doing stuff.
/* detect freebsd gettimeofday bug */
#include <stdio.h>
#include <unistd.h>
#include <sys/time.h>
check()
{
struct timeval tv;
if (gettimeofday(&tv, NULL) == -1) {
perror("gettimeofday");
return;
}
if (tv.tv_usec < 0 || tv.tv_usec >= 1000000) {
printf("cazart! gettimeofday returned impossible tv_usec value of %d\n", tv.tv_usec);
}
}
main()
{
int i;
for (i = 0; i < 1000000; i++) {
int j;
for (j = 0; i < 100; j++) {
check();
}
usleep((i % 8) + 1);
}
}
>Fix:
Locate and repair bug in kernel that allows invalid tv_usec
calls to be returned.
>Release-Note:
>Audit-Trail:
>Unformatted:
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