LXR linux-old/kernel/softirq.c

   1/*
   2 *      linux/kernel/softirq.c
   3 *
   4 *      Copyright (C) 1992 Linus Torvalds
   5 *
   6 * do_bottom_half() runs at normal kernel priority: all interrupts
   7 * enabled.  do_bottom_half() is atomic with respect to itself: a
   8 * bottom_half handler need not be re-entrant.
   9 */
  10
  11#include <linux/ptrace.h>
  12#include <linux/errno.h>
  13#include <linux/kernel_stat.h>
  14#include <linux/signal.h>
  15#include <linux/sched.h>
  16#include <linux/interrupt.h>
  17#include <linux/mm.h>
  18#include <linux/smp.h>
  19#include <linux/smp_lock.h>
  20
  21#include <asm/system.h>
  22#include <asm/io.h>
  23#include <asm/irq.h>
  24#include <asm/bitops.h>
  25#include <asm/atomic.h>
  26
  27/* intr_count died a painless death... -DaveM */
  28
  29int bh_mask_count[32];
  30unsigned long bh_active = 0;
  31unsigned long bh_mask = 0;
  32void (*bh_base[32])(void);
  33
  34/*
  35 * This needs to make sure that only one bottom half handler
  36 * is ever active at a time. We do this without locking by
  37 * doing an atomic increment on the intr_count, and checking
  38 * (nonatomically) against 1. Only if it's 1 do we schedule
  39 * the bottom half.
  40 *
  41 * Note that the non-atomicity of the test (as opposed to the
  42 * actual update) means that the test may fail, and _nobody_
  43 * runs the handlers if there is a race that makes multiple
  44 * CPU's get here at the same time. That's ok, we'll run them
  45 * next time around.
  46 */
  47static inline void run_bottom_halves(void)
  48{
  49        unsigned long active;
  50        void (**bh)(void);
  51
  52        active = get_active_bhs();
  53        clear_active_bhs(active);
  54        bh = bh_base;
  55        do {
  56                if (active & 1)
  57                        (*bh)();
  58                bh++;
  59                active >>= 1;
  60        } while (active);
  61}
  62
  63asmlinkage void do_bottom_half(void)
  64{
  65        if (softirq_trylock()) {
  66                int cpu = smp_processor_id();
  67
  68                if (hardirq_trylock(cpu)) {
  69                        __sti();
  70                        run_bottom_halves();
  71                        hardirq_endlock(cpu);
  72                }
  73                softirq_endlock();
  74        }
  75}
  76