[BUG - HRT patch] disabling timer hangs system when multiple over runs

From: Fleischer, Julie N (julie.n.fleischer@intel.com)
Date: Mon Jan 13 2003 - 13:26:46 EST


George -
I'm testing your 2.5.54-bk1 high-res-timers patches and am working on
debugging an issue I'm seeing where my system hangs (i.e., doesn't accept
input and I have to reboot). It happens when I'm disabling the timer by
setting the it_value to 0. I've been able to nail it down to know that it
only happens when you have generated multiple overruns (i.e., when I set up
a repeating timer and block it for > 1 timer expiry, my system then hangs
when I try to disable that timer -- I'm disabling before unblocking the
signals).

I know "system hang" is not very descriptive. If you have input on what
types of logs I should be looking at to figure out what's really going on or
other ways I can debug, I'll do that.

I have added the tests I'm using to reproduce this issue to
http://posixtest.sf.net. The original one where I noticed it was
posixtestsuite/conformance/interfaces/timer_gettime/2-3.c after Jim
Houston's bug fix. Then, I added
posixtestsuite/conformance/interfaces/timer_settime/3-2.c and 3-3.c to help
me get to root cause. To view the issue, you can either run
timer_gettime/2-3.c, or change timer_settime/3-3.c to use a repeating timer
(in nsecs). I have included the latter below.

==> One related ignorant question I had is I wanted to test this against
your latest version (2.5.54-bk6), but when I went today to get the bk
patches for 2.5.54, I couldn't find them. Are those only available for the
current kernel version? That makes sense -- I should have been quicker.
But, just wanted to check if there was another way for me to get that
version.

Additional information is below:
kernel used = 2.5.54-bk1
HRT patches applied =
 hrtimers-core-2.5.54-bk1-1.0.patch
 hrtimers-hrposix-2.5.54-bk1-1.0.patch
 hrtimers-i386-2.5.54-bk1-1.0.patch
 hrtimers-posix-2.5.54-bk1-1.0.patch
 hrtimers-support-2.5.52-1.0.patch

Thanks.
- Julie Fleischer

timer_settime/3-3.c - with modifications to show issue
/*
 * 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 if value.it_value = 0, the timer is disarmed. Test by
 * disarming a currently armed and blocked timer.
 *
 * 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>
#include "posixtest.h"

#define TIMEREXPIRENSEC 10000000
#define SLEEPTIME 1

#define SIGTOTEST SIGALRM

void handler(int signo)
{
        printf("OK to be in once\n");
}

int main(int argc, char *argv[])
{
        sigset_t set;
        struct sigevent ev;
        struct sigaction act;
        timer_t tid;
        struct itimerspec its;
        struct timespec ts;

        ev.sigev_notify = SIGEV_SIGNAL;
        ev.sigev_signo = SIGTOTEST;

        if (sigemptyset(&set) != 0) {
                perror("sigemptyset() did not return success\n");
                return PTS_UNRESOLVED;
        }

        if (sigaddset(&set, SIGTOTEST) != 0) {
                perror("sigaddset() did not return success\n");
                return PTS_UNRESOLVED;
        }

        if (sigprocmask(SIG_SETMASK, &set, NULL) != 0) {
                perror("sigprocmask() did not return success\n");
                return PTS_UNRESOLVED;
        }

        if (timer_create(CLOCK_REALTIME, &ev, &tid) != 0) {
                perror("timer_create() did not return success\n");
                return PTS_UNRESOLVED;
        }

        /*
         * First set up timer to be blocked
         */
        its.it_interval.tv_sec = 0;
        its.it_interval.tv_nsec = 5*TIMEREXPIRENSEC;
        its.it_value.tv_sec = 0;
        its.it_value.tv_nsec = TIMEREXPIRENSEC;

        printf("setup first timer\n");
        if (timer_settime(tid, 0, &its, NULL) != 0) {
                perror("timer_settime() did not return success\n");
                return PTS_UNRESOLVED;
        }

        printf("sleep\n");
        sleep(SLEEPTIME);
        printf("awoke\n");

        /*
         * Second, set value.it_value = 0 and set up handler to catch
         * signal.
         */
        act.sa_handler=handler;
        act.sa_flags=0;

        if (sigemptyset(&act.sa_mask) == -1) {
                perror("Error calling sigemptyset\n");
                return PTS_UNRESOLVED;
        }
        if (sigaction(SIGTOTEST, &act, 0) == -1) {
                perror("Error calling sigaction\n");
                return PTS_UNRESOLVED;
        }

        its.it_interval.tv_sec = 0;
        its.it_interval.tv_nsec = 0;
        its.it_value.tv_sec = 0;
        its.it_value.tv_nsec = 0;

        printf("setup second timer\n");
        if (timer_settime(tid, 0, &its, NULL) != 0) {
                perror("timer_settime() did not return success\n");
                return PTS_UNRESOLVED;
        }

        printf("unblock\n");
        if (sigprocmask(SIG_UNBLOCK, &set, NULL) != 0) {
                perror("sigprocmask() did not return success\n");
                return PTS_UNRESOLVED;
        }

        /*
         * Ensure sleep for TIMEREXPIRE seconds not interrupted
         */
        ts.tv_sec=SLEEPTIME;
        ts.tv_nsec=0;

        printf("sleep again\n");
        if (nanosleep(&ts, NULL) == -1) {
                printf("nanosleep() interrupted\n");
                printf("Test FAILED\n");
                return PTS_FAIL;
        }

        printf("Test PASSED\n");
        return PTS_PASS;
}

**These views are not necessarily those of my employer.**
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