* Re: [PATCH 2.6] fix POSIX timers expire before their scheduled time
2005-03-17 6:29 ` George Anzinger
@ 2005-03-17 6:48 ` Hong Liu
0 siblings, 0 replies; 3+ messages in thread
From: Hong Liu @ 2005-03-17 6:48 UTC (permalink / raw)
To: george; +Cc: linux-kernel
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On Thu, 2005-03-17 at 14:29, George Anzinger wrote:
> Liu, Hong wrote:
> > POSIX says: POSIX timers should not expire before their scheduled time.
> >
> > Due to the timer started between jiffies, there are cases that the timer
> > will expire before its scheduled time.
> > This patch ensures timers will not expire early.
> >
> > --- a/kernel/posix-timers.c 2005-03-10 15:46:27.329333664 +0800
> > +++ b/kernel/posix-timers.c 2005-03-10 15:50:11.884196136 +0800
> > @@ -957,7 +957,8 @@
> > &expire_64, &(timr->wall_to_prev))) {
> > return -EINVAL;
> > }
> > - timr->it_timer.expires = (unsigned long)expire_64;
> > + timr->it_timer.expires = (unsigned long)expire_64 + 1;
> > tstojiffie(&new_setting->it_interval, clock->res, &expire_64);
> > timr->it_incr = (unsigned long)expire_64;
> >
> Has this happened?? The following code (in adjust_abs_time()) is supposed to
> prevent this sort of thing:
>
> if (oc.tv_sec | oc.tv_nsec) {
> oc.tv_nsec += clock->res;
> timespec_norm(&oc);
> }
>
> Also, we run rather extensive tests for this sort of thing.
>
The attached case from PosixTestSuite(http://posixtest.sourceforge.net)
failed on IA64 platform.
And if I changed the time interval to N*clock_res in this case, it will
also fail on IA32 platform.
BTW, I can't find the code piece you mentioned in 2.6.11 kernel.
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/*
* Copyright (c) 2002, Intel Corporation. All rights reserved.
* Created by: julie.n.fleischer REMOVE-THIS AT intel DOT com
* This file is licensed under the GPL license. For the full content
* of this license, see the COPYING file at the top level of this
* source tree.
*
* Test that timers are not allowed to expire before their scheduled
* time.
*
* Test for a variety of timer values on relative timers.
*
* For this test, signal SIGTOTEST will be used, clock CLOCK_REALTIME
* will be used.
*/
#include <time.h>
#include <signal.h>
#include <stdio.h>
#include <unistd.h>
#include <stdlib.h>
#define PTS_PASS 0
#define PTS_FAIL 1
#define PTS_UNRESOLVED 2
#define PTS_UNSUPPORTED 4
#define PTS_UNTESTED 5
#define SIGTOTEST SIGALRM
#define TIMERVALUESEC 2
#define TIMERINTERVALSEC 5
#define INCREMENT 1
#define ACCEPTABLEDELTA 1
#define NUMTESTS 6
static int timeroffsets[NUMTESTS][2] = { {0, 30000000}, {1, 0},
{1, 30000000}, {2, 0},
{1, 5000}, {1, 5} };
int main(int argc, char *argv[])
{
struct sigevent ev;
timer_t tid;
struct itimerspec its;
struct timespec tsbefore, tsafter;
sigset_t set;
int sig;
int i;
int failure = 0;
unsigned long totalnsecs, testnsecs; // so long was we are < 2.1 seconds, we should be safe
/*
* set up signal set containing SIGTOTEST that will be used
* in call to sigwait immediately after timer is set
*/
if (sigemptyset(&set) == -1 ) {
perror("sigemptyset() failed\n");
return PTS_UNRESOLVED;
}
if (sigaddset(&set, SIGTOTEST) == -1) {
perror("sigaddset() failed\n");
return PTS_UNRESOLVED;
}
if (sigprocmask (SIG_BLOCK, &set, NULL) == -1) {
perror("sigprocmask() failed\n");
return PTS_UNRESOLVED;
}
/*
* set up timer to perform action SIGTOTEST on expiration
*/
ev.sigev_notify = SIGEV_SIGNAL;
ev.sigev_signo = SIGTOTEST;
if (timer_create(CLOCK_REALTIME, &ev, &tid) != 0) {
perror("timer_create() did not return success\n");
return PTS_UNRESOLVED;
}
for (i = 0; i < NUMTESTS; i++) {
its.it_interval.tv_sec = 0; its.it_interval.tv_nsec = 0;
its.it_value.tv_sec = timeroffsets[i][0];
its.it_value.tv_nsec = timeroffsets[i][1];
printf("Test for value %d sec %d nsec\n",
(int) its.it_value.tv_sec,
(int) its.it_value.tv_nsec);
if (clock_gettime(CLOCK_REALTIME, &tsbefore) != 0) {
perror("clock_gettime() did not return success\n");
return PTS_UNRESOLVED;
}
if (timer_settime(tid, 0, &its, NULL) != 0) {
perror("timer_settime() did not return success\n");
return PTS_UNRESOLVED;
}
if (sigwait(&set, &sig) == -1) {
perror("sigwait() failed\n");
return PTS_UNRESOLVED;
}
if (clock_gettime(CLOCK_REALTIME, &tsafter) != 0) {
perror("clock_gettime() did not return success\n");
return PTS_UNRESOLVED;
}
printf("tsbefore: sec--%lu, nsec--%lu\n", tsbefore.tv_sec,
tsbefore.tv_nsec);
printf("tsafter: sec--%lu, nsec--%lu\n", tsafter.tv_sec,
tsafter.tv_nsec);
totalnsecs = (unsigned long) (tsafter.tv_sec-tsbefore.tv_sec)*
1000000000 +
(tsafter.tv_nsec-tsbefore.tv_nsec);
testnsecs = (unsigned long) its.it_value.tv_sec*1000000000 +
its.it_value.tv_nsec;
printf("total %lu test %lu\n", totalnsecs, testnsecs);
if (totalnsecs < testnsecs) {
printf("FAIL: Expired %ld < %ld\n", totalnsecs,
testnsecs);
failure = 1;
}
}
if (timer_delete(tid) != 0) {
perror("timer_delete() did not return success\n");
return PTS_UNRESOLVED;
}
if (failure) {
printf("timer_settime() failed on at least one value\n");
return PTS_FAIL;
} else {
printf("Test PASSED\n");
return PTS_PASS;
}
}
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