NetBSD/lib/libpthread/pthread_suspend_np.3

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.Dd July 9, 2010
.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
.Fa thread
given as argument.
If
.Fa 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
.Fa thread
will remain blocked until
.Fn pthread_resume_np
is called on it.
In other words,
.Fn pthread_resume_np
resumes the
.Fa thread
given as argument, if it was suspended.
.Sh RETURN VALUES
Both functions return 0 on success and an error number indicating the
reason for the failure.
.Sh COMPATIBILITY
These functions are non-standard extensions.
.Sh ERRORS
The
.Fn pthread_suspend_np
function may fail if:
.Bl -tag -width Er
.It Bq Er EDEADLK
The thread requested to suspend was the currently running thread.
.It Bq Er ESRCH
The supplied
.Fa thread
was invalid.
.El
.Pp
The
.Fn pthread_resume_np
function may fail if:
.Bl -tag -width Er
.It Bq Er ESRCH
The supplied
.Fa thread
was invalid.
.El
.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
the
.Nx
implementation does not check if the
.Fa 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