November 12, 2003 PTHREAD_SUSPEND_NP 3

### NAME

pthread_suspend_np, pthread_resume_np - suspend/resume the given thread

### LIBRARY

POSIX Thread Library (libpthread, -lpthread)

### SYNOPSIS

```int` pthread_suspend_np(```pthread_t thread`)
```int` pthread_resume_np(```pthread_t thread`)

### DESCRIPTION

The pthread_suspend_np(``) function suspends the thread given as argument. If thread is the currently running thread as returned by pthread_self(3), the function fails and returns ```EDEADLK`. Otherwise, it removes the named thread from the running queue, and adds it to the suspended queue. The thread will remain blocked until pthread_resume_np(``) is called on it.

pthread_resume_np(``) resumes the thread given as argument, if it was suspended.

### RETURN VALUES

The pthread_suspend_np(``) function returns 0 on success and an error number indicating the reason for the failure. The pthread_resume_np(``) function always returns 0.

### ERRORS

pthread_suspend_np(``) shall fail if:

[```EDEADLK`]
  The thread requested to suspend was the currently running thread.

pthread_resume_np(``) never fails.

### NOTES

Some pthread_suspend_np(``) implementations may allow suspending the current thread. This is dangerous, because the semantics of the function would then require the scheduler to schedule another thread, causing a thread context switch. Since that context switch can happen in a signal handler by someone calling pthread_suspend_np(``) in a signal handler, this is currently not allowed.

In pthread_resume_np(``) we don't check if the thread argument is not already suspended. Some implementations might return an error condition if pthread_resume_np(``) is called on a non-suspended thread.

### SEE ALSO

pthread_attr_setcreatesuspend_np(3), pthread_self(3)