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