标签：linux内核 软中断 do_softirq 下半部
asmlinkage void __init start_kernel(void)
{
char * command_line;
extern struct kernel_param __start___param[], __stop___param[];
smp_setup_processor_id();
......
softirq_init();//初始化软中断
......
/* Do the rest non-__init'ed, we're now alive */
rest_init();
}
void __init softirq_init(void)
{
int cpu;
for_each_possible_cpu(cpu) {
int i;
per_cpu(tasklet_vec, cpu).tail =
&per_cpu(tasklet_vec, cpu).head;
per_cpu(tasklet_hi_vec, cpu).tail =
&per_cpu(tasklet_hi_vec, cpu).head;
for (i = 0; i < NR_SOFTIRQS; i++)
INIT_LIST_HEAD(&per_cpu(softirq_work_list[i], cpu));
}
register_hotcpu_notifier(&remote_softirq_cpu_notifier);
//此处注册两个软中断
open_softirq(TASKLET_SOFTIRQ, tasklet_action); open_softirq(HI_SOFTIRQ, tasklet_hi_action);
}
void open_softirq(int nr, void (*action)(struct softirq_action *))
{
softirq_vec[nr].action = action;
}
struct softirq_action
{
void (*action)(struct softirq_action *);
}
static struct softirq_action softirq_vec[NR_SOFTIRQS] __cacheline_aligned_in_smp;
/* PLEASE, avoid to allocate new softirqs, if you need not _really_ high
frequency threaded job scheduling. For almost all the purposes
tasklets are more than enough. F.e. all serial device BHs et
al. should be converted to tasklets, not to softirqs.
*/
enum
{
HI_SOFTIRQ=0,
TIMER_SOFTIRQ,
NET_TX_SOFTIRQ,
NET_RX_SOFTIRQ,
BLOCK_SOFTIRQ,
BLOCK_IOPOLL_SOFTIRQ,
TASKLET_SOFTIRQ,
SCHED_SOFTIRQ,
HRTIMER_SOFTIRQ,
RCU_SOFTIRQ, /* Preferable RCU should always be the last softirq */
NR_SOFTIRQS
};
asmlinkage void do_softirq(void) { __u32 pending; unsigned long flags; //如果在硬件中断环境中就退出，软中断不可以在硬件中断上下文或者是在软中断环境中使用，使用in_interrupt()来防止软中断嵌套，和抢占硬中断环境。 if (in_interrupt()) return; //禁止本地中断 local_irq_save(flags); pending = local_softirq_pending();
//如果有软中断要处理，则进入__do_softirq()
if (pending) __do_softirq(); local_irq_restore(flags);
asmlinkage void __do_softirq(void)
{
struct softirq_action *h;
__u32 pending;
int max_restart = MAX_SOFTIRQ_RESTART;
int cpu;
pending = local_softirq_pending(); //pending用于保留待处理软中断32位位图
account_system_vtime(current);
__local_bh_disable((unsigned long)__builtin_return_address(0));
lockdep_softirq_enter();
cpu = smp_processor_id();
restart:
/* Reset the pending bitmask before enabling irqs */
set_softirq_pending(0);
local_irq_enable();
h = softirq_vec;
do {
if (pending & 1) { //如果pending第n位被设置为1，那么处理第n位对应类型的软中断
int prev_count = preempt_count();
kstat_incr_softirqs_this_cpu(h - softirq_vec);
trace_softirq_entry(h, softirq_vec);
h->action(h); //执行软中断处理函数
trace_softirq_exit(h, softirq_vec);
if (unlikely(prev_count != preempt_count())) {
printk(KERN_ERR "huh, entered softirq %td %s %p"
"with preempt_count %08x,"
" exited with %08x?\n", h - softirq_vec,
softirq_to_name[h - softirq_vec],
h->action, prev_count, preempt_count());
preempt_count() = prev_count;
}
rcu_bh_qs(cpu);
}
h++;
pending >>= 1; //pending右移一位，循环检查其每一位
} while (pending); //直到pending变为0，pending最多32位，所以循环最多执行32次。
local_irq_disable();
pending = local_softirq_pending();
if (pending && --max_restart)
goto restart;
if (pending)
wakeup_softirqd();
lockdep_softirq_exit();
account_system_vtime(current);
_local_bh_enable();
}
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标签：linux内核 软中断 do_softirq 下半部
原文地址：http://blog.csdn.net/shallnet/article/details/47114737
