thr_suspend(3C) Standard C Library Functions thr_suspend(3C)
NAME
thr_suspend, thr_continue - suspend or continue thread execution
SYNOPSIS
cc -mt [ flag... ] file...[ library... ]
#include <thread.h>
int thr_suspend(thread_t target_thread);
int thr_continue(thread_t target_thread);
DESCRIPTION
The thr_suspend() function immediately suspends the execution of the thread specified by target_thread. On successful return from thr_sus-
pend(), the suspended thread is no longer executing. Once a thread is suspended, subsequent calls to thr_suspend() have no effect.
The thr_continue() function resumes the execution of a suspended thread. Once a suspended thread is continued, subsequent calls to thr_con-
tinue() have no effect.
A suspended thread will not be awakened by any mechanism other than a call to thr_continue(). Signals and the effect of calls tomu-
tex_unlock(3C), rw_unlock(3C), sema_post(3C), cond_signal(3C), and cond_broadcast(3C) remain pending until the execution of the thread is
resumed by thr_continue().
RETURN VALUES
If successful, the thr_suspend() and thr_continue() functions return 0. Otherwise, a non-zero value is returned to indicate the error.
ERRORS
The thr_suspend() and thr_continue() functions will fail if:
ESRCH The target_thread cannot be found in the current process.
ATTRIBUTES
See attributes(5) for descriptions of the following attributes:
+-----------------------------+-----------------------------+
| ATTRIBUTE TYPE | ATTRIBUTE VALUE |
+-----------------------------+-----------------------------+
|MT-Level |MT-Safe |
+-----------------------------+-----------------------------+
SEE ALSO
thr_create(3C), thr_join(3C), attributes(5), standards(5)
WARNINGS
The thr_suspend() function is extremely difficult to use safely because it suspends the target thread with no concern for the target
thread's state. The target thread could be holding locks, waiting for a lock, or waiting on a condition variable when it is unconditionally
suspended. The thread will not run until thr_continue() is applied, regardless of any calls to mutex_unlock(), cond_signal(), or
cond_broadcast() by other threads. Its existence on a sleep queue can interfere with the waking up of other threads that are on the same
sleep queue.
The thr_suspend() and thr_continue() functions should be avoided. Mechanisms that involve the cooperation of the targeted thread, such as
mutex locks and condition variables, should be employed instead.
SunOS 5.11 22 Mar 2002 thr_suspend(3C)