cpu_idle(9) [netbsd man page]

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

NAME

     cpu_idle -- machine-dependent processor idling interface

SYNOPSIS

     #include <sys/cpu.h>

     void
     cpu_idle(void);

DESCRIPTION

     cpu_idle() is called by machine-independent code when the processor has nothing to do.  It can be used to conserve the processor power, for
     example.

     cpu_idle() returns immediately if cpu_need_resched() has been called for the processor after the last call of cpu_idle() or cpu_did_resched()
     on the processor.	cpu_idle() returns as soon as possible when cpu_need_resched() is called for the processor.  Otherwise, it returns when-
     ever it likes.

     cpu_idle() is called at IPL_NONE, without any locks held.

EXAMPLES

     The simplest (and, in some cases, the best) implementation of cpu_idle() is the following.

	     void
	     cpu_idle(void)
	     {
		     /* nothing */
	     }

SEE ALSO

     cpu_need_resched(9), cpu_switchto(9), intro(9), spl(9)

BSD
								  April 20, 2007							       BSD

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

NAME

     userret -- return path to user-mode execution

SYNOPSIS

     #include <sys/lwp.h>
     #include <sys/sched.h>

     void
     userret(struct lwp *l);

DESCRIPTION

     The userret() function is executed after processing a trap (e.g., a system call or interrupt) before returning to user-mode execution.  The
     implementation is machine dependent and is never invoked from machine-independent code.  The function prototype for each architecture may be
     different to the prototype above, however the functionally provided by the userret() function on each architecture is essentially the same.

     Specifically, the userret() function performs the following procedure:

	   o   Detect a change in the signal disposition of the current process and invoke postsig(9) to post the signal to the process.  This may
	       occur when the outcome of the trap or syscall posted a signal to the process (e.g., invalid instruction trap).

	   o   Check the want_resched flag to see if the scheduler requires the current process to be preempted by invoking preempt(9) (see
	       cpu_need_resched(9)).  This may occur if the clock interrupt causes the scheduler to determine that the current process has com-
	       pleted its time slice.

	   o   Update the scheduler state.

SEE ALSO

     cpu_need_resched(9), postsig(9), preempt(9), scheduler(9)

BSD
								 December 20, 2005							       BSD