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243 struct softirq_action

244 {

245 void (*action)(struct softirq_action *);

246 void *data;

247 };

struct softirq_action softirq_vec[32]；

local_softirq_pending

softirq_vec

……

遍历softirq_vec数组，依次执行action（data）函数

229 do {

其中有两个比较特殊的地方0和6指定的函数为tasklet_hi_action(NULL)和tasklet_action(NULL)

230 if (pending & 1) {

231 trace_irq_softirq_entry(h, softirq_vec);

232 h->action(h);

233 trace_irq_softirq_exit(h, softirq_vec);

234 rcu_bh_qsctr_inc(cpu);

首先找到tasklet_vec每cpu变量链表的头

235 }

然后赋予listwhile循环从list指向的地方开始执行

236 h++;

同时把count=1的（锁住的）再次放回到tasklet_vec链表中去

237 pending >>= 1;

处理完返回；

238 } while (pending);

遍历软中断数组softirq_vec

系统初始化期间start_kernel函数中调用softirq_init对软中断进行初始化。

471 void __init softirq_init(void)

329 void open_softirq(int nr, void (*action)(struct softirq_action*), void *data)

472 {

330 {

473 open_softirq(TASKLET_SOFTIRQ, tasklet_action, NULL);

331 softirq_vec[nr].data = data;

474 open_softirq(HI_SOFTIRQ, tasklet_hi_action, NULL);

332 softirq_vec[nr].action = action;

475 }

333 }

将数组strcut softirq_action softirq_vec[32]对应的[TASKLET_SOFTIRQ]和[HI_SOFTIRQ]设置好；

222 /* PLEASE, avoid to allocate new softirqs, if you need not _really_ high

223 frequency threaded job scheduling. For almost all the purposes

224 tasklets are more than enough. F.e. all serial device BHs et

225 al. should be converted to tasklets, not to softirqs.

226 */

227

228 enum

229 {

230 HI_SOFTIRQ=0,

231 TIMER_SOFTIRQ,

232 NET_TX_SOFTIRQ,

233 NET_RX_SOFTIRQ,

234 BLOCK_SOFTIRQ,

235 BLOCK_IOPOLL_SOFTIRQ,

236 TASKLET_SOFTIRQ

237 };

软中断还有扩展的余地：struct softirq_action softirq_vec[32]；数组只用了前6项

处理软中断的时机do_IRQ完成后也就是说硬中断完成后，立马去执行软中断，在软中断处理函数中遍历10次softirq_vec数组处理激活的软中断。（__softirq_pending相应位为

320 void fastcall raise_softirq(unsigned int nr)

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321 {

323

324 local_irq_save(flags);

325 raise_softirq_irqoff(nr);

326 local_irq_restore(flags);

327 }

激活软中断。所谓的激活什么?

#define __raise_softirq_irqoff(nr) do { or_softirq_pending(1UL << (nr)); } while (0)

#define or_softirq_pending(x) (local_softirq_pending() |= (x))

//找到本地CPU的per_cpu_irq_stat变量找出其中的成员__softirq_pending|=(1<<(nr)) 设相应位为1；

7 typedef struct {

12 } ____cacheline_aligned irq_cpustat_t;

DECLARE_PER_CPU(irq_cpustat_t, irq_stat);

extern irq_cpustat_t per_cpu_irq_stat;

do_softirq遍历softirq_vec数组

443 void tasklet_init(struct tasklet_struct *t,

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444 void (*func)(unsigned long), unsigned long data)

445 {

446 t->next = NULL;

447 t->state = 0;

448 atomic_set(&t->count, 0);

449 t->func = func;

450 t->data = data;

451 }

336 struct tasklet_head

337 {

338 struct tasklet_struct *list;

339 };

343 static DEFINE_PER_CPU(struct tasklet_head, tasklet_vec) = { NULL };

344 static DEFINE_PER_CPU(struct tasklet_head, tasklet_hi_vec) = { NULL };

277 struct tasklet_struct

do_softirq会扫描这个数组

278 {

softirq_vec

279 struct tasklet_struct *next;

……

280 unsigned long state;

281 atomic_t count;

282 void (*func)(unsigned long);

283 unsigned long data;

per-cpu variable

284 };

tasklet_hi_vec

…

cpu1

tasklet_hi_vec

…

cpu0

tasklet_vec

cpu1

tasklet_struct

tasklet_vec

NULL

cpu0

state

count

func

data

286 #define DECLARE_TASKLET(name, func, data) \

443 void tasklet_init(struct tasklet_struct *t,

287 struct tasklet_struct name = { NULL, 0, ATOMIC_INIT(0), func, data }

288

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289 #define DECLARE_TASKLET_DISABLED(name, func, data) \

444 void (*func)(unsigned long), unsigned long data)

290 struct tasklet_struct name = { NULL, 0, ATOMIC_INIT(1), func, data }

445 {

446 t->next = NULL;

静态的定义一个名字为name的truct tasklet_struct

447 t->state = 0;

448 atomic_set(&t->count, 0);

323 static inline void tasklet_schedule(struct tasklet_struct *t)

449 t->func = func;

450 t->data = data;

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451 }

动态的初始化一个tasklet_struct结构体，现在还有插入到taslet_vec或者tasklet_hi_let链表中所以还没有机会执行

324 {

那么在哪里插入到tasklet_struct链表中的呢？tasklet_schedule（）函数中

325 if (!test_and_set_bit(TASKLET_STATE_SCHED, &t->state))

//测试t指向的tasklet_struct是否已经在per-cpu链表中

326 __tasklet_schedule(t);

327 }

372 static void tasklet_action(struct softirq_action *a)

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373 {

374 struct tasklet_struct *list;

375

377 list = __get_cpu_var(tasklet_vec).list;

378 __get_cpu_var(tasklet_vec).list = NULL;

380

382 struct tasklet_struct *t = list;

383

384 list = list->next;

385

386 if (tasklet_trylock(t)) {

387 if (!atomic_read(&t->count)) {

388 if (!test_and_clear_bit(TASKLET_STATE_SCHED, &t->state))

391 t->func(t->data);

393 tasklet_unlock(t);

394 continue;

395 }

396 tasklet_unlock(t);

397 }

398

400 t->next = __get_cpu_var(tasklet_vec).list;

//将count=1锁住的tasklet继续留在softirq_vec per-cpu变量中。

401 __get_cpu_var(tasklet_vec).list = t;

402 __raise_softirq_irqoff(TASKLET_SOFTIRQ);

404 }

405 }

455 void tasklet_kill(struct tasklet_struct *t)

346 void fastcall __tasklet_schedule(struct tasklet_struct *t)

/* [previous][next][first][last][top][bottom][index][help] */

456 {

347 {

457 if (in_interrupt())

348 unsigned long flags;

458 printk("Attempt to kill tasklet from interrupt\n");

349

459

350 local_irq_save(flags);

460 while (test_and_set_bit(TASKLET_STATE_SCHED, &t->state)) {

351 t->next = __get_cpu_var(tasklet_vec).list;

461 do

352 __get_cpu_var(tasklet_vec).list = t;

462 yield();

353 raise_softirq_irqoff(TASKLET_SOFTIRQ);

463 while (test_bit(TASKLET_STATE_SCHED, &t->state));

354 local_irq_restore(flags);

464 }

355 }

465 tasklet_unlock_wait(t);

//将tasklet_struct插入到softirq_vec链表的第一个位置

466 clear_bit(TASKLET_STATE_SCHED, &t->state);

467 }

//自杀不是他杀~

static LIST_HEAD(workqueues);

63 struct workqueue_struct {

64 struct cpu_workqueue_struct *cpu_wq;

65 const char *name;

#define create_workqueue(name) __create_workqueue((name), 0)

66 struct list_head list; /* Empty if single thread */

67 };

struct workqueue_struct *wq

alloc_percpu分配

struct cpu_workqueue_struct

cpu_wq

lock

name

remove_sequeuece

list

insert_sequeue

work_struct

worklist

pending

more_work

entry

work_done

func

data

thread

wq_data

struct workqueue_struct *wq

run_depth

timer

struct list_head workqueues;

cpu_wq

name

list

NULL

346 if (is_single_threaded(wq))

347 p = kthread_create(worker_thread, cwq, "%s", wq->name);

348 else

349 p = kthread_create(worker_thread, cwq, "%s/%d", wq->name, cpu);

进程描述符中的thread_info字段中有一个32位的preempt_counter字段，0-7位为抢占计数器，用于记录显式禁用内核抢占的次数；8-15位为软中断计数器，记录可延迟函数被禁用的次数；16-27为硬中断计数器，表示中断处理程序的嵌套数（irq_enter()递增它，irq_exit()递减它）；28位为PREEMPT_ACTIVE标志。只要内核检测到preempt_counter整体不为0，就不会进行内核抢占，这个简单的探测一下子保证了对众多不能抢占的情况的检测。

IRQ handler type mismatch for IRQ 0

[] setup_irq+0x176/0x18a

[] irq_handle+0x0/0xc [per_cpu_3_1]

[] request_irq+0x7c/0x98

[] hello_init+0x63f/0x64c [per_cpu_3_1]

[] sys_init_module+0x1aed/0x1caa

[] audit_syscall_entry+0x15a/0x18c

[] syscall_call+0x7/0xb

=======================

调用setup_irq进行中断初始化时，需要手动的分配一个irqaction的结构体空间，并把irq_desc

中的action指针指向这个结构体。