Manpages - pthread_tryjoin_np.3

pthread_tryjoin_np, pthread_timedjoin_np - try to join with a terminated thread

  #define _GNU_SOURCE /* See feature_test_macros(7) */
  #include <pthread.h>

  int pthread_tryjoin_np(pthread_t thread, void **retval);
  int pthread_timedjoin_np(pthread_t thread, void **retval,
   const struct timespec *abstime);

Compile and link with -pthread.

These functions operate in the same way as *pthread_join*(3), except for the differences described on this page.

The *pthread_tryjoin_np*() function performs a nonblocking join with the thread thread, returning the exit status of the thread in *retval. If thread has not yet terminated, then instead of blocking, as is done by *pthread_join*(3), the call returns an error.

The pthread_timedjoin_np*() function performs a join-with-timeout. If thread has not yet terminated, then the call blocks until a maximum time, specified in abstime, measured against the *CLOCK_REALTIME clock. If the timeout expires before thread terminates, the call returns an error. The abstime argument is a structure of the following form, specifying an absolute time measured since the Epoch (see *time*(2)):

  struct timespec {
      time_t tv_sec;     /* seconds */
      long   tv_nsec;    /* nanoseconds */
  };

On success, these functions return 0; on error, they return an error number.

These functions can fail with the same errors as *pthread_join*(3). *pthread_tryjoin_np*() can in addition fail with the following error:

EBUSY

thread had not yet terminated at the time of the call.

*pthread_timedjoin_np*() can in addition fail with the following errors:

EINVAL

abstime value is invalid (tv_sec is less than 0 or tv_nsec is greater than 1e9).

ETIMEDOUT

The call timed out before thread terminated.

pthread_timedjoin_np*() never returns the error *EINTR.

These functions first appeared in glibc in version 2.3.3.

For an explanation of the terms used in this section, see *attributes*(7).

These functions are nonstandard GNU extensions; hence the suffix “_np” (nonportable) in the names.

The pthread_timedjoin_np*() function measures time by internally calculating a relative sleep interval that is then measured against the *CLOCK_MONOTONIC clock instead of the CLOCK_REALTIME clock. Consequently, the timeout is unaffected by discontinuous changes to the CLOCK_REALTIME clock.

The following code waits to join for up to 5 seconds:

  struct timespec ts;
  int s;

  ...

  if (clock_gettime(CLOCK_REALTIME, &ts) == -1) {
      /* Handle error */
  }

  ts.tv_sec += 5;

  s = pthread_timedjoin_np(thread, NULL, &ts);
  if (s != 0) {
      /* Handle error */
  }

*clock_gettime*(2), *pthread_exit*(3), *pthread_join*(3), *pthreads*(7)

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