NAME
cpu_need_resched —
context switch notification
SYNOPSIS
#include
<sys/cpu.h>
void
cpu_need_resched(struct
cpu_info *ci, int
flags);
DESCRIPTION
Thecpu_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:
- Set a per-processor flag which is checked by userret(9) when returning to user-mode execution.
- Post an asynchronous software trap (AST).
- Send an inter processor interrupt to wake up cpu_idle(9).