PTHREAD_TRYJOIN_NP

Section: Linux Programmer's Manual (3)
Updated: 2020-12-21
Page Index

NAME

pthread_tryjoin_np, pthread_timedjoin_np - try to join with a terminated thread

SYNOPSIS

#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.

DESCRIPTION

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 */ };

RETURN VALUE

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

ERRORS

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:

ETIMEDOUT: The call timed out before thread terminated.
EINVAL: abstime value is invalid (tv_sec is less than 0 or tv_nsec is greater than 1e9).

pthread_timedjoin_np() never returns the error EINTR.

VERSIONS

These functions first appeared in glibc in version 2.3.3.

ATTRIBUTES

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

Interface	Attribute	Value
pthread_tryjoin_np(), pthread_timedjoin_np()	Thread safety	MT-Safe

CONFORMING TO

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

EXAMPLES

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 */ }

BUGS

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.

COLOPHON

This page is part of release 5.10 of the Linux man-pages project. A description of the project, information about reporting bugs, and the latest version of this page, can be found at https://www.kernel.org/doc/man-pages/.