THR_WAKE(2)               FreeBSD System Calls Manual              THR_WAKE(2)

NAME
     thr_wake - wake up the suspended thread

LIBRARY
     Standard C Library (libc, -lc)

SYNOPSIS
     #include <sys/thr.h>

     int
     thr_wake(long id);

DESCRIPTION
     This function is intended for implementing threading.  Normal
     applications should use pthread_cond_timedwait(3) together with
     pthread_cond_broadcast(3) for typical safe suspension with cooperation of
     the thread being suspended, or pthread_suspend_np(3) and
     pthread_resume_np(3) in some specific situations, instead.

     Passing the thread identifier of the calling thread (see thr_self(2)) to
     thr_wake() sets a thread's flag to cause the next signal-interruptible
     sleep of that thread in the kernel to fail immediately with the EINTR
     error.  The flag is cleared by an interruptible sleep attempt or by a
     call to thr_suspend(2).  This is used by the system threading library to
     implement cancellation.

     If id is not equal to the current thread identifier, the specified thread
     is woken up if suspended by the thr_suspend(2) system call.  If the
     thread is not suspended at the time of the thr_wake call, the wake is
     remembered and the next attempt of the thread to suspend itself with the
     thr_suspend(2) results in immediate return with success.  Only one wake
     is remembered.

RETURN VALUES
     The thr_wake() function returns the value 0 if successful; otherwise the
     value -1 is returned and the global variable errno is set to indicate the
     error.

ERRORS
     The thr_wake() operation returns these errors:

     [ESRCH]            The specified thread was not found or does not belong
                        to the process of the calling thread.

SEE ALSO
     ps(1), thr_self(2), thr_suspend(2), pthread_cancel(3),
     pthread_resume_np(3), pthread_suspend_np(3)

STANDARDS
     The thr_suspend() system call is non-standard and is used by 1:1
     Threading Library (libthr, -lthr) to implement IEEE Std 1003.1-2001
     ("POSIX.1") pthread(3) functionality.

HISTORY
     The thr_suspend() system call first appeared in FreeBSD 5.2.

FreeBSD 13.1-RELEASE-p6           May 5, 2020          FreeBSD 13.1-RELEASE-p6