中断六
继续分析asm_do_IRQ里的irq_exit
/kernel/softirq.c
/*
* Exit an interrupt context. Process softirqs if needed and possible:
*/
void irq_exit(void)
{
account_system_vtime(current); //空函数include/linux/hardirq.h
trace_hardirq_exit(); //中断上下文切换
sub_preempt_count(IRQ_EXIT_OFFSET);
if (!in_interrupt() && local_softirq_pending()) //判断是否有硬件中断里，如果不是，判断是否有软件中断需要执行
invoke_softirq();
#ifdef CONFIG_NO_HZ
/* Make sure that timer wheel updates are propagated */
rcu_irq_exit();
if (idle_cpu(smp_processor_id()) && !in_interrupt() && !need_resched())
tick_nohz_stop_sched_tick(0);
#endif
preempt_enable_no_resched();
}
./include/linux/irqflags.h:
# define trace_hardirq_exit() do { current->hardirq_context--; } while (0)
/kernel/softirq.c
#ifdef __ARCH_IRQ_EXIT_IRQS_DISABLED
# define invoke_softirq() __do_softirq()
#else
# define invoke_softirq() do_softirq()
#endif
asmlinkage void do_softirq(void)
{
__u32 pending;
unsigned long flags;
if (in_interrupt())
return;
local_irq_save(flags);
pending = local_softirq_pending();
if (pending)
__do_softirq();
local_irq_restore(flags);
}
#define MAX_SOFTIRQ_RESTART 10 //执行的循环次数，即软中断个数
asmlinkage void __do_softirq(void)
{
struct softirq_action *h;
__u32 pending;
int max_restart = MAX_SOFTIRQ_RESTART;
int cpu;
pending = local_softirq_pending();
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; //此定义了软中断将要执行的函数，包括TIMER TASKLET HIxxxx的 在open_softirq中将其赋值了目前发现有三个地方，一个是时钟那里init_timers，另外两个是中断出事化那里
do {
if (pending & 1) {
int prev_count = preempt_count();
kstat_incr_softirqs_this_cpu(h - softirq_vec);
trace_softirq_entry(h, softirq_vec);
h->action(h); //调用了open_softirq里的软中断执行函数
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_qsctr_inc(cpu);
}
h++;
pending >>= 1;
} while (pending);
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();
}
kernel/softirq.c
void __init softirq_init(void)
{
................................
open_softirq(TASKLET_SOFTIRQ, tasklet_action);
open_softirq(HI_SOFTIRQ, tasklet_hi_action);
}
kernel/softirq.c
static void tasklet_action(struct softirq_action *a)
{
struct tasklet_struct *list;
local_irq_disable();
list = __get_cpu_var(tasklet_vec).head;
__get_cpu_var(tasklet_vec).head = NULL;
__get_cpu_var(tasklet_vec).tail = &__get_cpu_var(tasklet_vec).head;
local_irq_enable();
while (list) {
struct tasklet_struct *t = list;
list = list->next; //整个tasklet_struct链表遍历
if (tasklet_trylock(t)) {
if (!atomic_read(&t->count)) {
if (!test_and_clear_bit(TASKLET_STATE_SCHED, &t->state))
BUG();
t->func(t->data); //执行函数
tasklet_unlock(t);
continue;
}
tasklet_unlock(t);
}
local_irq_disable();
t->next = NULL;
*__get_cpu_var(tasklet_vec).tail = t;
__get_cpu_var(tasklet_vec).tail = &(t->next);
__raise_softirq_irqoff(TASKLET_SOFTIRQ);
local_irq_enable();
}
}
static void tasklet_hi_action(struct softirq_action *a)
{
struct tasklet_struct *list;
local_irq_disable();
list = __get_cpu_var(tasklet_hi_vec).head;
__get_cpu_var(tasklet_hi_vec).head = NULL;
__get_cpu_var(tasklet_hi_vec).tail = &__get_cpu_var(tasklet_hi_vec).head;
local_irq_enable();
while (list) {
struct tasklet_struct *t = list;
list = list->next; //遍历链表
if (tasklet_trylock(t)) {
if (!atomic_read(&t->count)) {
if (!test_and_clear_bit(TASKLET_STATE_SCHED, &t->state))
BUG();
t->func(t->data); //执行函数
tasklet_unlock(t);
continue;
}
tasklet_unlock(t);
}
local_irq_disable();
t->next = NULL;
*__get_cpu_var(tasklet_hi_vec).tail = t;
__get_cpu_var(tasklet_hi_vec).tail = &(t->next);
__raise_softirq_irqoff(HI_SOFTIRQ);
local_irq_enable();
}
}