cpu_need_resched(9) - NetBSD Manual Pages

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CPU_NEED_RESCHED(9)    NetBSD 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() typi-
     cally 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).


SEE ALSO

     sched_4bsd(9), userret(9)

NetBSD 6.1.3                     July 31, 2010                    NetBSD 6.1.3