Date: Fri, 21 Jan 2000 10:03:30 -0600 (CST) From: "James C. Beyer" <beyer@cs.umn.edu> To: Sabrina Minshall <sabrina@accesscom.com> Cc: hackers@FreeBSD.ORG Subject: Re: PR kern/14034: gettimeofday() returns negative value? Message-ID: <Pine.SOL.4.21.0001210952460.24651-100000@kepler.cs.umn.edu> In-Reply-To: <Pine.BSF.4.21.0001210017590.51684-100000@resnet.uoregon.edu>
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Actually, a line like temp =t1->tv_usec + 1000000;
or using some other temp to save the t1 data before it is permuted will
make the program work perfectly. t1->tv_usec += 1000000; Kills the
correct value when t2 is updated. The another option would be to stop
using pointers in the function call. ie:
#include <sys/param.h>
#include <sys/types.h>
#include <sys/time.h>
#include <sys/select.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <assert.h>
#include <unistd.h>
int
time_elapsed(struct timeval t1, struct timeval t2)
{
int s, ms;
s = t1.tv_sec - t2.tv_sec;
assert((s >= 0));
if (s != 0) {
if (t1.tv_usec < t2.tv_usec) {
s--;
t1.tv_usec += 1000000;
}
}
ms = s * 1000000 + (t1.tv_usec - t2.tv_usec);
return (ms);
}
int
main()
{
struct timeval tv1, tv2;
int run = 0;
int diff;
if (gettimeofday(&tv1, NULL) < 0) {
perror("gettimeofday");
}
tv2.tv_usec = tv1.tv_usec;
tv2.tv_sec = tv1.tv_sec;
for (;;) {
usleep(9000);
if (gettimeofday(&tv1, NULL) < 0) {
perror("gettimeofday");
}
/*
* diff in usec.
*/
diff = time_elapsed(tv1, tv2);
if (diff < 0) {
printf("-ve tvdiff %d\n", diff);
printf("%ld %ld %ld %ld\n",
tv1.tv_sec, tv1.tv_usec,
tv2.tv_sec, tv2.tv_usec);
printf("run = %d\n", run);
assert(0);
}
tv2.tv_usec = tv1.tv_usec;
tv2.tv_sec = tv1.tv_sec;
run++;
}
return (0);
}
works fine been running for 5 minutes without a hitch.
Don't update a value if you don't really want it changed outside a
function.
jcb
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