A few questions regarding times() usage in SNMPv3.
First, there is a bug in Linux times() that will return -1 a small
time frame just before times() wrap. See
http://git.kernel.org/?p=linux/kernel/git/torvalds/linux-2.6.git;a=commit;h=e3d5a27d5862b6425d0879272e24abecf7245105
for a fix but only for some arches.
A workaround for this problem:
static unsigned long snmp_times(void)
{
#if defined(GNU_LINUX)
unsigned long ret;
errno = 0;
ret = times(NULL); /* Linux can handle NULL */
/* Workaround broken syscall impl.
* Fixed in 2.6.29 for some archs
*/
if (errno)
ret = (unsigned long) (-errno);
return ret;
/* probably one can do this instead:
ret = times(NULL);
if (ret == ~0) {
errno = 0;
ret = times(NULL);
if (ret == ~0 && errno)
ret = (unsigned long) (-errno);
}
return ret;
*/
#else
struct tms dummy; /* Only return value is used */
return times(&dummy);
#endif
Secondly, Linux times() can take a NULL arg and that saves
a lot of work in the kernel.
Now to my real question, I don't understand why you need to
handle wrapping especially:
1540 clock_t now = times(&dummy);
1541 /* fixme: -1 is fault code... */
1542 unsigned int result;
1543
1544 if (now < snmpv3startClock) {
1545 result = UINT_MAX - snmpv3startClock + now;
1546 } else {
1547 result = now - snmpv3startClock;
1548 }
1549 if (result < lastcalltime) {
1550 /* wrapped */
1551 wrapcounter++;
1552 }
1553 lastcalltime = result;
1554 result = (UINT_MAX/clockticks)*wrapcounter +
result/clockticks;
Should be possible to just do:
static unsigned long secs;
now = snmp_times();
diff = now - lastcalltime;
diff /= clockticks;
if (!diff)
return secs; /* no change */
lastcalltime = now;
secs += diff;
return secs;
Jocke
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