netbsd man page for yield

PREEMPT(9)						   BSD Kernel Developer's Manual						PREEMPT(9)

NAME
     preempt, yield -- general preempt and yield functions

SYNOPSIS
     #include <sys/sched.h>

     void
     preempt(void);

     #include <sys/proc.h>

     void
     yield(void);

DESCRIPTION
     The preempt() function puts the current LWP back on the system run queue and performs an involuntary context switch.  The yield() function is
     mostly same as preempt(), except that it performs a voluntary context switch.

     These functions drop the kernel lock before switching and re-acquire it before returning.

BSD
								   July 3, 2007 							       BSD