NetBSD/lib/libpthread/pthread_suspend_np.3

.\" $NetBSD: pthread_suspend_np.3,v 1.2 2003/11/12 11:58:34 wiz Exp $
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.\" by Christos Zoulas.
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.Dd November 12, 2003
.Dt PTHREAD_SUSPEND_NP 3
.Os
.Sh NAME
.Nm pthread_suspend_np ,
.Nm pthread_resume_np
.Nd suspend/resume the given thread
.Sh LIBRARY
.Lb libpthread
.Sh SYNOPSIS
.In pthread.h
.Ft int
.Fn pthread_suspend_np "pthread_t thread"
.Ft int
.Fn pthread_resume_np "pthread_t thread"
.Sh DESCRIPTION
The
.Fn pthread_suspend_np
function suspends the
.Ar thread
given as argument.
If
.Ar thread
is the currently running thread as returned by
.Xr pthread_self 3 ,
the function fails and returns
.Er EDEADLK .
Otherwise, it removes the named thread from the running queue, and
adds it to the suspended queue.
The
.Ar thread
will remain blocked until
.Fn pthread_resume_np
is called on it.
.Pp
.Fn pthread_resume_np
resumes the
.Ar thread
given as argument, if it was suspended.
.Sh RETURN VALUES
The
.Fn pthread_suspend_np
function returns 0 on success and an error number indicating the
reason for the failure.
The
.Fn pthread_resume_np
function always returns 0.
.Sh ERRORS
.Fn pthread_suspend_np
shall fail if:
.Bl -tag -width Er
.It Bq Er EDEADLK
The thread requested to suspend was the currently running thread.
.El
.Pp
.Fn pthread_resume_np
never fails.
.Sh NOTES
Some
.Fn 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
.Fn pthread_suspend_np
in a signal handler, this is currently not allowed.
.Pp
In
.Fn pthread_resume_np
we don't check if the
.Ar thread
argument is not already suspended.
Some implementations might return an error condition if
.Fn pthread_resume_np
is called on a non-suspended thread.
.Sh SEE ALSO
.Xr pthread_attr_setcreatesuspend_np 3 ,
.Xr pthread_self 3