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

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

NAME

     cpu_need_resched -- context switch notification

SYNOPSIS

     #include <sys/cpu.h>

     void
     cpu_need_resched(struct cpu_info *ci, int flags);

DESCRIPTION

     The cpu_need_resched() function is the machine-independent interface for the scheduler to notify machine-dependent code that a context switch
     from the current LWP, on the cpu ci, is required.	This event may occur if a higher priority LWP appears on the run queue or if the current
     LWP has exceeded its time slice.

     If RESCHED_KPREEMPT flag is specified in flags and __HAVE_PREEMPTION C pre-processor macro is defined in <machine/intr.h>, machine-dependent
     code should make a context switch happen as soon as possible even if the cpu is running the kernel code.

     If RESCHED_IMMED flag is specified in flags, machine-dependent code should make a context switch happen as soon as possible.  In that case,
     for example, if ci is not the current processor, cpu_need_resched() typically issues an inter processor call to the processor to make it
     notice the need of a context switch as soon as possible.

     Typically, the cpu_need_resched() function will perform the following operations:

	   o   Set a per-processor flag which is checked by userret(9) when returning to user-mode execution.

	   o   Post an asynchronous software trap (AST).

	   o   Send an inter processor interrupt to wake up cpu_idle(9).

SEE ALSO

     sched_4bsd(9), userret(9)

BSD
								   July 31, 2010							       BSD