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Re: [LTP] [PATCH v3 2/2] open_posix_testsuite/../mq_timedsend/12-1: fix race
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From: Jan S. <jst...@re...> - 2013-08-12 15:32:29
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----- Original Message -----
> From: ch...@su...
> To: "Jan Stancek" <jst...@re...>
> Cc: ltp...@li...
> Sent: Monday, 12 August, 2013 4:43:15 PM
> Subject: Re: [LTP] [PATCH v3 2/2] open_posix_testsuite/../mq_timedsend/12-1: fix race
>
> Hi!
> > Signed-off-by: Jan Stancek <jst...@re...>
> > ---
> > Changes in v3:
> > remove SAFE() macro
> > convert pipes to mutex and condition
> >
> > .../conformance/interfaces/mq_timedsend/12-1.c | 175
> > ++++++++++++--------
> > 1 files changed, 107 insertions(+), 68 deletions(-)
> >
> > diff --git
> > a/testcases/open_posix_testsuite/conformance/interfaces/mq_timedsend/12-1.c
> > b/testcases/open_posix_testsuite/conformance/interfaces/mq_timedsend/12-1.c
> > index 29780d0..fdcb6ec 100644
> > ---
> > a/testcases/open_posix_testsuite/conformance/interfaces/mq_timedsend/12-1.c
> > +++
> > b/testcases/open_posix_testsuite/conformance/interfaces/mq_timedsend/12-1.c
> > @@ -39,19 +39,23 @@
> > #define MSGSTR "0123456789"
> > #define BUFFER 40
> > #define MAXMSG 10
> > +#define TIMEOUT 10 /* seconds mq_timedsend will block */
> > +#define SIGNAL_DELAY_MS 50 /* delay in ms between 2 signals */
> > +#define STATE_THREAD_READY 1
> > +#define STATE_DONE_SENDING 2
> >
> > -#define INTHREAD 0
> > -#define INMAIN 1
> > +#define handle_error_en(en, msg) \
> > + do { errno = en; perror(msg); exit(PTS_UNRESOLVED); } while (0)
>
> Maybe error_and_exit() would be a bit better name, but that is very
> minor.
>
> > -/* manual semaphore */
> > -int sem;
> > +/* variable to indicate how many times signal handler was called */
> > +static volatile sig_atomic_t in_handler;
> >
> > -/* flag to indicate signal handler was called */
> > -int in_handler;
> > +/* errno returned by mq_timedsend() */
> > +static int mq_timedsend_errno = -1;
> >
> > -/* flag to indicate that errno was set to eintr when mq_timedsend()
> > - * was interruped. */
> > -int errno_eintr;
> > +static int state;
> > +pthread_mutex_t mutex;
> > +pthread_cond_t cond;
> >
> > /*
> > * This handler is just used to catch the signal and stop sleep (so the
> > @@ -59,12 +63,46 @@ int errno_eintr;
> > */
> > void justreturn_handler(int signo)
> > {
> > - /* Indicate that the signal handler was called */
> > - in_handler = 1;
> > - return;
> > + in_handler++;
> > }
> >
> > -void *a_thread_func()
> > +void set_state(int n)
> > +{
> > + int ret;
> > +
> > + ret = pthread_mutex_lock(&mutex);
> > + if (ret != 0)
> > + handle_error_en(ret, "set_state pthread_mutex_lock");
> > +
> > + state = n;
> > + ret = pthread_cond_signal(&cond);
> > + if (ret != 0)
> > + handle_error_en(ret, "set_state pthread_cond_signal");
> > +
> > + ret = pthread_mutex_unlock(&mutex);
> > + if (ret != 0)
> > + handle_error_en(ret, "set_state pthread_mutex_unlock");
> > +}
> > +
> > +void wait_for_state(int n)
> > +{
> > + int ret;
> > +
> > + ret = pthread_mutex_lock(&mutex);
> > + if (ret != 0)
> > + handle_error_en(ret, "wait_for_state pthread_mutex_lock");
> > +
> > + while (state != n) {
> > + ret = pthread_cond_wait(&cond, &mutex);
> > + if (ret != 0)
> > + handle_error_en(ret, "pthread_cond_wait");
> > + }
> > + ret = pthread_mutex_unlock(&mutex);
> > + if (ret != 0)
> > + handle_error_en(ret, "wait_for_state pthread_mutex_unlock");
> > +}
>
> Hmm, that gets unnecessary complicated :(
Back to pipes? :-)
>
> And all we need is to get first thread wait until the second is ready
> and then the second until the first has finished sending signals. I
> wonder if pthread_barrier or two wouldn't be easier way around.
This sounds promising, I'll look into using barriers for v4.
Thanks,
Jan
>
> > +void *a_thread_func(void *arg)
> > {
> > int i, ret;
> > struct sigaction act;
> > @@ -86,101 +124,102 @@ void *a_thread_func()
> > attr.mq_maxmsg = MAXMSG;
> > attr.mq_msgsize = BUFFER;
> > gqueue = mq_open(gqname, O_CREAT | O_RDWR, S_IRUSR | S_IWUSR, &attr);
> > - if (gqueue == (mqd_t) - 1) {
> > - perror("mq_open() did not return success");
> > - pthread_exit((void *)PTS_UNRESOLVED);
> > - return NULL;
> > - }
> > + if (gqueue == (mqd_t) -1)
> > + handle_error_en(errno, "mq_open");
> >
> > - /* mq_timedsend will block for 10 seconds when it waits */
> > - ts.tv_sec = time(NULL) + 10;
> > + /* mq_timedsend will block for TIMEOUT seconds when it waits */
> > + ts.tv_sec = time(NULL) + TIMEOUT;
> > ts.tv_nsec = 0;
> >
> > /* Tell main it can go ahead and start sending SIGUSR1 signal */
> > - sem = INMAIN;
> > + set_state(STATE_THREAD_READY);
> >
> > for (i = 0; i < MAXMSG + 1; i++) {
> > ret = mq_timedsend(gqueue, msgptr, strlen(msgptr), 1, &ts);
> > - if (ret != -1)
> > + if (ret != -1)
> > continue;
> >
> > + mq_timedsend_errno = errno;
> > if (errno == EINTR) {
> > - if (mq_unlink(gqname) != 0) {
> > - perror("mq_unlink() did not return success");
> > - pthread_exit((void *)PTS_UNRESOLVED);
> > - return NULL;
> > - }
> > + if (mq_unlink(gqname) != 0)
> > + handle_error_en(errno, "mq_unlink");
> > printf("thread: mq_timedsend interrupted by signal"
> > " and correctly set errno to EINTR\n");
> > - errno_eintr = 1;
> > + wait_for_state(STATE_DONE_SENDING);
> > pthread_exit((void *)PTS_PASS);
> > - return NULL;
> > } else {
> > printf("mq_timedsend not interrupted by signal or"
> > " set errno to incorrect code: %d\n", errno);
> > + wait_for_state(STATE_DONE_SENDING);
> > pthread_exit((void *)PTS_FAIL);
> > - return NULL;
> > }
> > }
> >
> > - /* Tell main that it the thread did not block like it should have */
> > - sem = INTHREAD;
> > -
> > - perror("Error: thread never blocked\n");
> > + mq_timedsend_errno = 0;
> > + printf("Error: mq_timedsend wasn't interrupted\n");
> > + wait_for_state(STATE_DONE_SENDING);
> > pthread_exit((void *)PTS_FAIL);
> > - return NULL;
> > }
> >
> > int main(void)
> > {
> > pthread_t new_th;
> > - int i;
> > + int i = 0, ret;
> >
> > - /* Initialized values */
> > - i = 0;
> > - in_handler = 0;
> > - errno_eintr = 0;
> > - sem = INTHREAD;
> > + ret = pthread_mutex_init(&mutex, NULL);
> > + if (ret != 0)
> > + handle_error_en(ret, "pthread_mutex_init");
>
> You can initialize the mutex statically with PTHRED_MUTEX_INITIALIZER.
>
> > - if (pthread_create(&new_th, NULL, a_thread_func, NULL) != 0) {
> > - perror("Error: in pthread_create\n");
> > - return PTS_UNRESOLVED;
> > - }
> > + ret = pthread_cond_init(&cond, NULL);
> > + if (ret != 0)
> > + handle_error_en(ret, "pthread_cond_init");
>
> Here as well with PTHREAD_COND_INIT.
>
> > - /* Wait for thread to set up handler for SIGUSR1 */
> > - while (sem == INTHREAD)
> > - sleep(1);
> > + ret = pthread_create(&new_th, NULL, a_thread_func, NULL);
> > + if (ret != 0)
> > + handle_error_en(ret, "pthread_create");
> >
> > - while ((i != 10) && (sem == INMAIN)) {
> > + /* wait for thread to start */
> > + wait_for_state(STATE_THREAD_READY);
> > +
> > + while (i < TIMEOUT*1000 && mq_timedsend_errno < 0) {
> > /* signal thread while it's in mq_timedsend */
> > - if (pthread_kill(new_th, SIGUSR1) != 0) {
> > - perror("Error: in pthread_kill\n");
> > - return PTS_UNRESOLVED;
> > - }
> > - i++;
> > + ret = pthread_kill(new_th, SIGUSR1);
> > + if (ret != 0)
> > + handle_error_en(ret, "pthread_kill");
> > + usleep(SIGNAL_DELAY_MS*1000);
> > + i += SIGNAL_DELAY_MS;
> > }
> >
> > - if (pthread_join(new_th, NULL) != 0) {
> > - perror("Error: in pthread_join()\n");
> > - return PTS_UNRESOLVED;
> > - }
> > + /* signal thread we are done sending SIGUSR1 */
> > + set_state(STATE_DONE_SENDING);
> > +
> > + ret = pthread_join(new_th, NULL);
> > + if (ret != 0)
> > + handle_error_en(ret, "pthread_join");
> >
> > /* Test to see if the thread blocked correctly in mq_timedsend,
> > * and if it returned EINTR when it caught the signal */
> > - if (errno_eintr != 1) {
> > - if (sem == INTHREAD) {
> > - printf("Test FAILED: mq_timedsend() never"
> > - " blocked for any timeout period.\n");
> > - return PTS_FAIL;
> > - }
> > -
> > - if (in_handler != 0) {
> > - perror("Error: signal SIGUSR1 was never received and/or"
> > - " the signal handler was never called.\n");
> > + if (mq_timedsend_errno != EINTR) {
> > + printf("Error: mq_timedsend was NOT interrupted\n");
> > + printf(" signal handler was called %d times\n", in_handler);
> > + printf(" SIGUSR1 signals sent: %d\n", i);
> > + printf(" last mq_timedsend errno: %d %s\n",
> > + mq_timedsend_errno, strerror(mq_timedsend_errno));
> > + if (in_handler == 0) {
> > + printf("Error: SIGUSR1 was never received\n");
> > return PTS_UNRESOLVED;
> > }
> > + return PTS_FAIL;
> > }
>
> --
> Cyril Hrubis
> ch...@su...
>
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