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TOMOYO Linux Cross Reference
Linux/net/sunrpc/sched.c

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  1 /*
  2  * linux/net/sunrpc/sched.c
  3  *
  4  * Scheduling for synchronous and asynchronous RPC requests.
  5  *
  6  * Copyright (C) 1996 Olaf Kirch, <okir@monad.swb.de>
  7  *
  8  * TCP NFS related read + write fixes
  9  * (C) 1999 Dave Airlie, University of Limerick, Ireland <airlied@linux.ie>
 10  */
 11 
 12 #include <linux/module.h>
 13 
 14 #include <linux/sched.h>
 15 #include <linux/interrupt.h>
 16 #include <linux/slab.h>
 17 #include <linux/mempool.h>
 18 #include <linux/smp.h>
 19 #include <linux/spinlock.h>
 20 #include <linux/mutex.h>
 21 #include <linux/freezer.h>
 22 
 23 #include <linux/sunrpc/clnt.h>
 24 
 25 #include "sunrpc.h"
 26 
 27 #if IS_ENABLED(CONFIG_SUNRPC_DEBUG)
 28 #define RPCDBG_FACILITY         RPCDBG_SCHED
 29 #endif
 30 
 31 #define CREATE_TRACE_POINTS
 32 #include <trace/events/sunrpc.h>
 33 
 34 /*
 35  * RPC slabs and memory pools
 36  */
 37 #define RPC_BUFFER_MAXSIZE      (2048)
 38 #define RPC_BUFFER_POOLSIZE     (8)
 39 #define RPC_TASK_POOLSIZE       (8)
 40 static struct kmem_cache        *rpc_task_slabp __read_mostly;
 41 static struct kmem_cache        *rpc_buffer_slabp __read_mostly;
 42 static mempool_t        *rpc_task_mempool __read_mostly;
 43 static mempool_t        *rpc_buffer_mempool __read_mostly;
 44 
 45 static void                     rpc_async_schedule(struct work_struct *);
 46 static void                      rpc_release_task(struct rpc_task *task);
 47 static void __rpc_queue_timer_fn(struct timer_list *t);
 48 
 49 /*
 50  * RPC tasks sit here while waiting for conditions to improve.
 51  */
 52 static struct rpc_wait_queue delay_queue;
 53 
 54 /*
 55  * rpciod-related stuff
 56  */
 57 struct workqueue_struct *rpciod_workqueue __read_mostly;
 58 struct workqueue_struct *xprtiod_workqueue __read_mostly;
 59 
 60 /*
 61  * Disable the timer for a given RPC task. Should be called with
 62  * queue->lock and bh_disabled in order to avoid races within
 63  * rpc_run_timer().
 64  */
 65 static void
 66 __rpc_disable_timer(struct rpc_wait_queue *queue, struct rpc_task *task)
 67 {
 68         if (task->tk_timeout == 0)
 69                 return;
 70         dprintk("RPC: %5u disabling timer\n", task->tk_pid);
 71         task->tk_timeout = 0;
 72         list_del(&task->u.tk_wait.timer_list);
 73         if (list_empty(&queue->timer_list.list))
 74                 del_timer(&queue->timer_list.timer);
 75 }
 76 
 77 static void
 78 rpc_set_queue_timer(struct rpc_wait_queue *queue, unsigned long expires)
 79 {
 80         queue->timer_list.expires = expires;
 81         mod_timer(&queue->timer_list.timer, expires);
 82 }
 83 
 84 /*
 85  * Set up a timer for the current task.
 86  */
 87 static void
 88 __rpc_add_timer(struct rpc_wait_queue *queue, struct rpc_task *task)
 89 {
 90         if (!task->tk_timeout)
 91                 return;
 92 
 93         dprintk("RPC: %5u setting alarm for %u ms\n",
 94                 task->tk_pid, jiffies_to_msecs(task->tk_timeout));
 95 
 96         task->u.tk_wait.expires = jiffies + task->tk_timeout;
 97         if (list_empty(&queue->timer_list.list) || time_before(task->u.tk_wait.expires, queue->timer_list.expires))
 98                 rpc_set_queue_timer(queue, task->u.tk_wait.expires);
 99         list_add(&task->u.tk_wait.timer_list, &queue->timer_list.list);
100 }
101 
102 static void rpc_rotate_queue_owner(struct rpc_wait_queue *queue)
103 {
104         struct list_head *q = &queue->tasks[queue->priority];
105         struct rpc_task *task;
106 
107         if (!list_empty(q)) {
108                 task = list_first_entry(q, struct rpc_task, u.tk_wait.list);
109                 if (task->tk_owner == queue->owner)
110                         list_move_tail(&task->u.tk_wait.list, q);
111         }
112 }
113 
114 static void rpc_set_waitqueue_priority(struct rpc_wait_queue *queue, int priority)
115 {
116         if (queue->priority != priority) {
117                 /* Fairness: rotate the list when changing priority */
118                 rpc_rotate_queue_owner(queue);
119                 queue->priority = priority;
120         }
121 }
122 
123 static void rpc_set_waitqueue_owner(struct rpc_wait_queue *queue, pid_t pid)
124 {
125         queue->owner = pid;
126         queue->nr = RPC_BATCH_COUNT;
127 }
128 
129 static void rpc_reset_waitqueue_priority(struct rpc_wait_queue *queue)
130 {
131         rpc_set_waitqueue_priority(queue, queue->maxpriority);
132         rpc_set_waitqueue_owner(queue, 0);
133 }
134 
135 /*
136  * Add new request to a priority queue.
137  */
138 static void __rpc_add_wait_queue_priority(struct rpc_wait_queue *queue,
139                 struct rpc_task *task,
140                 unsigned char queue_priority)
141 {
142         struct list_head *q;
143         struct rpc_task *t;
144 
145         INIT_LIST_HEAD(&task->u.tk_wait.links);
146         if (unlikely(queue_priority > queue->maxpriority))
147                 queue_priority = queue->maxpriority;
148         if (queue_priority > queue->priority)
149                 rpc_set_waitqueue_priority(queue, queue_priority);
150         q = &queue->tasks[queue_priority];
151         list_for_each_entry(t, q, u.tk_wait.list) {
152                 if (t->tk_owner == task->tk_owner) {
153                         list_add_tail(&task->u.tk_wait.list, &t->u.tk_wait.links);
154                         return;
155                 }
156         }
157         list_add_tail(&task->u.tk_wait.list, q);
158 }
159 
160 /*
161  * Add new request to wait queue.
162  *
163  * Swapper tasks always get inserted at the head of the queue.
164  * This should avoid many nasty memory deadlocks and hopefully
165  * improve overall performance.
166  * Everyone else gets appended to the queue to ensure proper FIFO behavior.
167  */
168 static void __rpc_add_wait_queue(struct rpc_wait_queue *queue,
169                 struct rpc_task *task,
170                 unsigned char queue_priority)
171 {
172         WARN_ON_ONCE(RPC_IS_QUEUED(task));
173         if (RPC_IS_QUEUED(task))
174                 return;
175 
176         if (RPC_IS_PRIORITY(queue))
177                 __rpc_add_wait_queue_priority(queue, task, queue_priority);
178         else if (RPC_IS_SWAPPER(task))
179                 list_add(&task->u.tk_wait.list, &queue->tasks[0]);
180         else
181                 list_add_tail(&task->u.tk_wait.list, &queue->tasks[0]);
182         task->tk_waitqueue = queue;
183         queue->qlen++;
184         /* barrier matches the read in rpc_wake_up_task_queue_locked() */
185         smp_wmb();
186         rpc_set_queued(task);
187 
188         dprintk("RPC: %5u added to queue %p \"%s\"\n",
189                         task->tk_pid, queue, rpc_qname(queue));
190 }
191 
192 /*
193  * Remove request from a priority queue.
194  */
195 static void __rpc_remove_wait_queue_priority(struct rpc_task *task)
196 {
197         struct rpc_task *t;
198 
199         if (!list_empty(&task->u.tk_wait.links)) {
200                 t = list_entry(task->u.tk_wait.links.next, struct rpc_task, u.tk_wait.list);
201                 list_move(&t->u.tk_wait.list, &task->u.tk_wait.list);
202                 list_splice_init(&task->u.tk_wait.links, &t->u.tk_wait.links);
203         }
204 }
205 
206 /*
207  * Remove request from queue.
208  * Note: must be called with spin lock held.
209  */
210 static void __rpc_remove_wait_queue(struct rpc_wait_queue *queue, struct rpc_task *task)
211 {
212         __rpc_disable_timer(queue, task);
213         if (RPC_IS_PRIORITY(queue))
214                 __rpc_remove_wait_queue_priority(task);
215         list_del(&task->u.tk_wait.list);
216         queue->qlen--;
217         dprintk("RPC: %5u removed from queue %p \"%s\"\n",
218                         task->tk_pid, queue, rpc_qname(queue));
219 }
220 
221 static void __rpc_init_priority_wait_queue(struct rpc_wait_queue *queue, const char *qname, unsigned char nr_queues)
222 {
223         int i;
224 
225         spin_lock_init(&queue->lock);
226         for (i = 0; i < ARRAY_SIZE(queue->tasks); i++)
227                 INIT_LIST_HEAD(&queue->tasks[i]);
228         queue->maxpriority = nr_queues - 1;
229         rpc_reset_waitqueue_priority(queue);
230         queue->qlen = 0;
231         timer_setup(&queue->timer_list.timer, __rpc_queue_timer_fn, 0);
232         INIT_LIST_HEAD(&queue->timer_list.list);
233         rpc_assign_waitqueue_name(queue, qname);
234 }
235 
236 void rpc_init_priority_wait_queue(struct rpc_wait_queue *queue, const char *qname)
237 {
238         __rpc_init_priority_wait_queue(queue, qname, RPC_NR_PRIORITY);
239 }
240 EXPORT_SYMBOL_GPL(rpc_init_priority_wait_queue);
241 
242 void rpc_init_wait_queue(struct rpc_wait_queue *queue, const char *qname)
243 {
244         __rpc_init_priority_wait_queue(queue, qname, 1);
245 }
246 EXPORT_SYMBOL_GPL(rpc_init_wait_queue);
247 
248 void rpc_destroy_wait_queue(struct rpc_wait_queue *queue)
249 {
250         del_timer_sync(&queue->timer_list.timer);
251 }
252 EXPORT_SYMBOL_GPL(rpc_destroy_wait_queue);
253 
254 static int rpc_wait_bit_killable(struct wait_bit_key *key, int mode)
255 {
256         freezable_schedule_unsafe();
257         if (signal_pending_state(mode, current))
258                 return -ERESTARTSYS;
259         return 0;
260 }
261 
262 #if IS_ENABLED(CONFIG_SUNRPC_DEBUG) || IS_ENABLED(CONFIG_TRACEPOINTS)
263 static void rpc_task_set_debuginfo(struct rpc_task *task)
264 {
265         static atomic_t rpc_pid;
266 
267         task->tk_pid = atomic_inc_return(&rpc_pid);
268 }
269 #else
270 static inline void rpc_task_set_debuginfo(struct rpc_task *task)
271 {
272 }
273 #endif
274 
275 static void rpc_set_active(struct rpc_task *task)
276 {
277         rpc_task_set_debuginfo(task);
278         set_bit(RPC_TASK_ACTIVE, &task->tk_runstate);
279         trace_rpc_task_begin(task, NULL);
280 }
281 
282 /*
283  * Mark an RPC call as having completed by clearing the 'active' bit
284  * and then waking up all tasks that were sleeping.
285  */
286 static int rpc_complete_task(struct rpc_task *task)
287 {
288         void *m = &task->tk_runstate;
289         wait_queue_head_t *wq = bit_waitqueue(m, RPC_TASK_ACTIVE);
290         struct wait_bit_key k = __WAIT_BIT_KEY_INITIALIZER(m, RPC_TASK_ACTIVE);
291         unsigned long flags;
292         int ret;
293 
294         trace_rpc_task_complete(task, NULL);
295 
296         spin_lock_irqsave(&wq->lock, flags);
297         clear_bit(RPC_TASK_ACTIVE, &task->tk_runstate);
298         ret = atomic_dec_and_test(&task->tk_count);
299         if (waitqueue_active(wq))
300                 __wake_up_locked_key(wq, TASK_NORMAL, &k);
301         spin_unlock_irqrestore(&wq->lock, flags);
302         return ret;
303 }
304 
305 /*
306  * Allow callers to wait for completion of an RPC call
307  *
308  * Note the use of out_of_line_wait_on_bit() rather than wait_on_bit()
309  * to enforce taking of the wq->lock and hence avoid races with
310  * rpc_complete_task().
311  */
312 int __rpc_wait_for_completion_task(struct rpc_task *task, wait_bit_action_f *action)
313 {
314         if (action == NULL)
315                 action = rpc_wait_bit_killable;
316         return out_of_line_wait_on_bit(&task->tk_runstate, RPC_TASK_ACTIVE,
317                         action, TASK_KILLABLE);
318 }
319 EXPORT_SYMBOL_GPL(__rpc_wait_for_completion_task);
320 
321 /*
322  * Make an RPC task runnable.
323  *
324  * Note: If the task is ASYNC, and is being made runnable after sitting on an
325  * rpc_wait_queue, this must be called with the queue spinlock held to protect
326  * the wait queue operation.
327  * Note the ordering of rpc_test_and_set_running() and rpc_clear_queued(),
328  * which is needed to ensure that __rpc_execute() doesn't loop (due to the
329  * lockless RPC_IS_QUEUED() test) before we've had a chance to test
330  * the RPC_TASK_RUNNING flag.
331  */
332 static void rpc_make_runnable(struct workqueue_struct *wq,
333                 struct rpc_task *task)
334 {
335         bool need_wakeup = !rpc_test_and_set_running(task);
336 
337         rpc_clear_queued(task);
338         if (!need_wakeup)
339                 return;
340         if (RPC_IS_ASYNC(task)) {
341                 INIT_WORK(&task->u.tk_work, rpc_async_schedule);
342                 queue_work(wq, &task->u.tk_work);
343         } else
344                 wake_up_bit(&task->tk_runstate, RPC_TASK_QUEUED);
345 }
346 
347 /*
348  * Prepare for sleeping on a wait queue.
349  * By always appending tasks to the list we ensure FIFO behavior.
350  * NB: An RPC task will only receive interrupt-driven events as long
351  * as it's on a wait queue.
352  */
353 static void __rpc_sleep_on_priority(struct rpc_wait_queue *q,
354                 struct rpc_task *task,
355                 rpc_action action,
356                 unsigned char queue_priority)
357 {
358         dprintk("RPC: %5u sleep_on(queue \"%s\" time %lu)\n",
359                         task->tk_pid, rpc_qname(q), jiffies);
360 
361         trace_rpc_task_sleep(task, q);
362 
363         __rpc_add_wait_queue(q, task, queue_priority);
364 
365         WARN_ON_ONCE(task->tk_callback != NULL);
366         task->tk_callback = action;
367         __rpc_add_timer(q, task);
368 }
369 
370 void rpc_sleep_on(struct rpc_wait_queue *q, struct rpc_task *task,
371                                 rpc_action action)
372 {
373         /* We shouldn't ever put an inactive task to sleep */
374         WARN_ON_ONCE(!RPC_IS_ACTIVATED(task));
375         if (!RPC_IS_ACTIVATED(task)) {
376                 task->tk_status = -EIO;
377                 rpc_put_task_async(task);
378                 return;
379         }
380 
381         /*
382          * Protect the queue operations.
383          */
384         spin_lock_bh(&q->lock);
385         __rpc_sleep_on_priority(q, task, action, task->tk_priority);
386         spin_unlock_bh(&q->lock);
387 }
388 EXPORT_SYMBOL_GPL(rpc_sleep_on);
389 
390 void rpc_sleep_on_priority(struct rpc_wait_queue *q, struct rpc_task *task,
391                 rpc_action action, int priority)
392 {
393         /* We shouldn't ever put an inactive task to sleep */
394         WARN_ON_ONCE(!RPC_IS_ACTIVATED(task));
395         if (!RPC_IS_ACTIVATED(task)) {
396                 task->tk_status = -EIO;
397                 rpc_put_task_async(task);
398                 return;
399         }
400 
401         /*
402          * Protect the queue operations.
403          */
404         spin_lock_bh(&q->lock);
405         __rpc_sleep_on_priority(q, task, action, priority - RPC_PRIORITY_LOW);
406         spin_unlock_bh(&q->lock);
407 }
408 EXPORT_SYMBOL_GPL(rpc_sleep_on_priority);
409 
410 /**
411  * __rpc_do_wake_up_task_on_wq - wake up a single rpc_task
412  * @wq: workqueue on which to run task
413  * @queue: wait queue
414  * @task: task to be woken up
415  *
416  * Caller must hold queue->lock, and have cleared the task queued flag.
417  */
418 static void __rpc_do_wake_up_task_on_wq(struct workqueue_struct *wq,
419                 struct rpc_wait_queue *queue,
420                 struct rpc_task *task)
421 {
422         dprintk("RPC: %5u __rpc_wake_up_task (now %lu)\n",
423                         task->tk_pid, jiffies);
424 
425         /* Has the task been executed yet? If not, we cannot wake it up! */
426         if (!RPC_IS_ACTIVATED(task)) {
427                 printk(KERN_ERR "RPC: Inactive task (%p) being woken up!\n", task);
428                 return;
429         }
430 
431         trace_rpc_task_wakeup(task, queue);
432 
433         __rpc_remove_wait_queue(queue, task);
434 
435         rpc_make_runnable(wq, task);
436 
437         dprintk("RPC:       __rpc_wake_up_task done\n");
438 }
439 
440 /*
441  * Wake up a queued task while the queue lock is being held
442  */
443 static void rpc_wake_up_task_on_wq_queue_locked(struct workqueue_struct *wq,
444                 struct rpc_wait_queue *queue, struct rpc_task *task)
445 {
446         if (RPC_IS_QUEUED(task)) {
447                 smp_rmb();
448                 if (task->tk_waitqueue == queue)
449                         __rpc_do_wake_up_task_on_wq(wq, queue, task);
450         }
451 }
452 
453 /*
454  * Wake up a queued task while the queue lock is being held
455  */
456 static void rpc_wake_up_task_queue_locked(struct rpc_wait_queue *queue, struct rpc_task *task)
457 {
458         rpc_wake_up_task_on_wq_queue_locked(rpciod_workqueue, queue, task);
459 }
460 
461 /*
462  * Wake up a task on a specific queue
463  */
464 void rpc_wake_up_queued_task_on_wq(struct workqueue_struct *wq,
465                 struct rpc_wait_queue *queue,
466                 struct rpc_task *task)
467 {
468         spin_lock_bh(&queue->lock);
469         rpc_wake_up_task_on_wq_queue_locked(wq, queue, task);
470         spin_unlock_bh(&queue->lock);
471 }
472 
473 /*
474  * Wake up a task on a specific queue
475  */
476 void rpc_wake_up_queued_task(struct rpc_wait_queue *queue, struct rpc_task *task)
477 {
478         spin_lock_bh(&queue->lock);
479         rpc_wake_up_task_queue_locked(queue, task);
480         spin_unlock_bh(&queue->lock);
481 }
482 EXPORT_SYMBOL_GPL(rpc_wake_up_queued_task);
483 
484 /*
485  * Wake up the next task on a priority queue.
486  */
487 static struct rpc_task *__rpc_find_next_queued_priority(struct rpc_wait_queue *queue)
488 {
489         struct list_head *q;
490         struct rpc_task *task;
491 
492         /*
493          * Service a batch of tasks from a single owner.
494          */
495         q = &queue->tasks[queue->priority];
496         if (!list_empty(q)) {
497                 task = list_entry(q->next, struct rpc_task, u.tk_wait.list);
498                 if (queue->owner == task->tk_owner) {
499                         if (--queue->nr)
500                                 goto out;
501                         list_move_tail(&task->u.tk_wait.list, q);
502                 }
503                 /*
504                  * Check if we need to switch queues.
505                  */
506                 goto new_owner;
507         }
508 
509         /*
510          * Service the next queue.
511          */
512         do {
513                 if (q == &queue->tasks[0])
514                         q = &queue->tasks[queue->maxpriority];
515                 else
516                         q = q - 1;
517                 if (!list_empty(q)) {
518                         task = list_entry(q->next, struct rpc_task, u.tk_wait.list);
519                         goto new_queue;
520                 }
521         } while (q != &queue->tasks[queue->priority]);
522 
523         rpc_reset_waitqueue_priority(queue);
524         return NULL;
525 
526 new_queue:
527         rpc_set_waitqueue_priority(queue, (unsigned int)(q - &queue->tasks[0]));
528 new_owner:
529         rpc_set_waitqueue_owner(queue, task->tk_owner);
530 out:
531         return task;
532 }
533 
534 static struct rpc_task *__rpc_find_next_queued(struct rpc_wait_queue *queue)
535 {
536         if (RPC_IS_PRIORITY(queue))
537                 return __rpc_find_next_queued_priority(queue);
538         if (!list_empty(&queue->tasks[0]))
539                 return list_first_entry(&queue->tasks[0], struct rpc_task, u.tk_wait.list);
540         return NULL;
541 }
542 
543 /*
544  * Wake up the first task on the wait queue.
545  */
546 struct rpc_task *rpc_wake_up_first_on_wq(struct workqueue_struct *wq,
547                 struct rpc_wait_queue *queue,
548                 bool (*func)(struct rpc_task *, void *), void *data)
549 {
550         struct rpc_task *task = NULL;
551 
552         dprintk("RPC:       wake_up_first(%p \"%s\")\n",
553                         queue, rpc_qname(queue));
554         spin_lock_bh(&queue->lock);
555         task = __rpc_find_next_queued(queue);
556         if (task != NULL) {
557                 if (func(task, data))
558                         rpc_wake_up_task_on_wq_queue_locked(wq, queue, task);
559                 else
560                         task = NULL;
561         }
562         spin_unlock_bh(&queue->lock);
563 
564         return task;
565 }
566 
567 /*
568  * Wake up the first task on the wait queue.
569  */
570 struct rpc_task *rpc_wake_up_first(struct rpc_wait_queue *queue,
571                 bool (*func)(struct rpc_task *, void *), void *data)
572 {
573         return rpc_wake_up_first_on_wq(rpciod_workqueue, queue, func, data);
574 }
575 EXPORT_SYMBOL_GPL(rpc_wake_up_first);
576 
577 static bool rpc_wake_up_next_func(struct rpc_task *task, void *data)
578 {
579         return true;
580 }
581 
582 /*
583  * Wake up the next task on the wait queue.
584 */
585 struct rpc_task *rpc_wake_up_next(struct rpc_wait_queue *queue)
586 {
587         return rpc_wake_up_first(queue, rpc_wake_up_next_func, NULL);
588 }
589 EXPORT_SYMBOL_GPL(rpc_wake_up_next);
590 
591 /**
592  * rpc_wake_up - wake up all rpc_tasks
593  * @queue: rpc_wait_queue on which the tasks are sleeping
594  *
595  * Grabs queue->lock
596  */
597 void rpc_wake_up(struct rpc_wait_queue *queue)
598 {
599         struct list_head *head;
600 
601         spin_lock_bh(&queue->lock);
602         head = &queue->tasks[queue->maxpriority];
603         for (;;) {
604                 while (!list_empty(head)) {
605                         struct rpc_task *task;
606                         task = list_first_entry(head,
607                                         struct rpc_task,
608                                         u.tk_wait.list);
609                         rpc_wake_up_task_queue_locked(queue, task);
610                 }
611                 if (head == &queue->tasks[0])
612                         break;
613                 head--;
614         }
615         spin_unlock_bh(&queue->lock);
616 }
617 EXPORT_SYMBOL_GPL(rpc_wake_up);
618 
619 /**
620  * rpc_wake_up_status - wake up all rpc_tasks and set their status value.
621  * @queue: rpc_wait_queue on which the tasks are sleeping
622  * @status: status value to set
623  *
624  * Grabs queue->lock
625  */
626 void rpc_wake_up_status(struct rpc_wait_queue *queue, int status)
627 {
628         struct list_head *head;
629 
630         spin_lock_bh(&queue->lock);
631         head = &queue->tasks[queue->maxpriority];
632         for (;;) {
633                 while (!list_empty(head)) {
634                         struct rpc_task *task;
635                         task = list_first_entry(head,
636                                         struct rpc_task,
637                                         u.tk_wait.list);
638                         task->tk_status = status;
639                         rpc_wake_up_task_queue_locked(queue, task);
640                 }
641                 if (head == &queue->tasks[0])
642                         break;
643                 head--;
644         }
645         spin_unlock_bh(&queue->lock);
646 }
647 EXPORT_SYMBOL_GPL(rpc_wake_up_status);
648 
649 static void __rpc_queue_timer_fn(struct timer_list *t)
650 {
651         struct rpc_wait_queue *queue = from_timer(queue, t, timer_list.timer);
652         struct rpc_task *task, *n;
653         unsigned long expires, now, timeo;
654 
655         spin_lock(&queue->lock);
656         expires = now = jiffies;
657         list_for_each_entry_safe(task, n, &queue->timer_list.list, u.tk_wait.timer_list) {
658                 timeo = task->u.tk_wait.expires;
659                 if (time_after_eq(now, timeo)) {
660                         dprintk("RPC: %5u timeout\n", task->tk_pid);
661                         task->tk_status = -ETIMEDOUT;
662                         rpc_wake_up_task_queue_locked(queue, task);
663                         continue;
664                 }
665                 if (expires == now || time_after(expires, timeo))
666                         expires = timeo;
667         }
668         if (!list_empty(&queue->timer_list.list))
669                 rpc_set_queue_timer(queue, expires);
670         spin_unlock(&queue->lock);
671 }
672 
673 static void __rpc_atrun(struct rpc_task *task)
674 {
675         if (task->tk_status == -ETIMEDOUT)
676                 task->tk_status = 0;
677 }
678 
679 /*
680  * Run a task at a later time
681  */
682 void rpc_delay(struct rpc_task *task, unsigned long delay)
683 {
684         task->tk_timeout = delay;
685         rpc_sleep_on(&delay_queue, task, __rpc_atrun);
686 }
687 EXPORT_SYMBOL_GPL(rpc_delay);
688 
689 /*
690  * Helper to call task->tk_ops->rpc_call_prepare
691  */
692 void rpc_prepare_task(struct rpc_task *task)
693 {
694         task->tk_ops->rpc_call_prepare(task, task->tk_calldata);
695 }
696 
697 static void
698 rpc_init_task_statistics(struct rpc_task *task)
699 {
700         /* Initialize retry counters */
701         task->tk_garb_retry = 2;
702         task->tk_cred_retry = 2;
703         task->tk_rebind_retry = 2;
704 
705         /* starting timestamp */
706         task->tk_start = ktime_get();
707 }
708 
709 static void
710 rpc_reset_task_statistics(struct rpc_task *task)
711 {
712         task->tk_timeouts = 0;
713         task->tk_flags &= ~(RPC_CALL_MAJORSEEN|RPC_TASK_KILLED|RPC_TASK_SENT);
714 
715         rpc_init_task_statistics(task);
716 }
717 
718 /*
719  * Helper that calls task->tk_ops->rpc_call_done if it exists
720  */
721 void rpc_exit_task(struct rpc_task *task)
722 {
723         task->tk_action = NULL;
724         if (task->tk_ops->rpc_call_done != NULL) {
725                 task->tk_ops->rpc_call_done(task, task->tk_calldata);
726                 if (task->tk_action != NULL) {
727                         WARN_ON(RPC_ASSASSINATED(task));
728                         /* Always release the RPC slot and buffer memory */
729                         xprt_release(task);
730                         rpc_reset_task_statistics(task);
731                 }
732         }
733 }
734 
735 void rpc_exit(struct rpc_task *task, int status)
736 {
737         task->tk_status = status;
738         task->tk_action = rpc_exit_task;
739         if (RPC_IS_QUEUED(task))
740                 rpc_wake_up_queued_task(task->tk_waitqueue, task);
741 }
742 EXPORT_SYMBOL_GPL(rpc_exit);
743 
744 void rpc_release_calldata(const struct rpc_call_ops *ops, void *calldata)
745 {
746         if (ops->rpc_release != NULL)
747                 ops->rpc_release(calldata);
748 }
749 
750 /*
751  * This is the RPC `scheduler' (or rather, the finite state machine).
752  */
753 static void __rpc_execute(struct rpc_task *task)
754 {
755         struct rpc_wait_queue *queue;
756         int task_is_async = RPC_IS_ASYNC(task);
757         int status = 0;
758 
759         dprintk("RPC: %5u __rpc_execute flags=0x%x\n",
760                         task->tk_pid, task->tk_flags);
761 
762         WARN_ON_ONCE(RPC_IS_QUEUED(task));
763         if (RPC_IS_QUEUED(task))
764                 return;
765 
766         for (;;) {
767                 void (*do_action)(struct rpc_task *);
768 
769                 /*
770                  * Perform the next FSM step or a pending callback.
771                  *
772                  * tk_action may be NULL if the task has been killed.
773                  * In particular, note that rpc_killall_tasks may
774                  * do this at any time, so beware when dereferencing.
775                  */
776                 do_action = task->tk_action;
777                 if (task->tk_callback) {
778                         do_action = task->tk_callback;
779                         task->tk_callback = NULL;
780                 }
781                 if (!do_action)
782                         break;
783                 trace_rpc_task_run_action(task, do_action);
784                 do_action(task);
785 
786                 /*
787                  * Lockless check for whether task is sleeping or not.
788                  */
789                 if (!RPC_IS_QUEUED(task))
790                         continue;
791                 /*
792                  * The queue->lock protects against races with
793                  * rpc_make_runnable().
794                  *
795                  * Note that once we clear RPC_TASK_RUNNING on an asynchronous
796                  * rpc_task, rpc_make_runnable() can assign it to a
797                  * different workqueue. We therefore cannot assume that the
798                  * rpc_task pointer may still be dereferenced.
799                  */
800                 queue = task->tk_waitqueue;
801                 spin_lock_bh(&queue->lock);
802                 if (!RPC_IS_QUEUED(task)) {
803                         spin_unlock_bh(&queue->lock);
804                         continue;
805                 }
806                 rpc_clear_running(task);
807                 spin_unlock_bh(&queue->lock);
808                 if (task_is_async)
809                         return;
810 
811                 /* sync task: sleep here */
812                 dprintk("RPC: %5u sync task going to sleep\n", task->tk_pid);
813                 status = out_of_line_wait_on_bit(&task->tk_runstate,
814                                 RPC_TASK_QUEUED, rpc_wait_bit_killable,
815                                 TASK_KILLABLE);
816                 if (status == -ERESTARTSYS) {
817                         /*
818                          * When a sync task receives a signal, it exits with
819                          * -ERESTARTSYS. In order to catch any callbacks that
820                          * clean up after sleeping on some queue, we don't
821                          * break the loop here, but go around once more.
822                          */
823                         dprintk("RPC: %5u got signal\n", task->tk_pid);
824                         task->tk_flags |= RPC_TASK_KILLED;
825                         rpc_exit(task, -ERESTARTSYS);
826                 }
827                 dprintk("RPC: %5u sync task resuming\n", task->tk_pid);
828         }
829 
830         dprintk("RPC: %5u return %d, status %d\n", task->tk_pid, status,
831                         task->tk_status);
832         /* Release all resources associated with the task */
833         rpc_release_task(task);
834 }
835 
836 /*
837  * User-visible entry point to the scheduler.
838  *
839  * This may be called recursively if e.g. an async NFS task updates
840  * the attributes and finds that dirty pages must be flushed.
841  * NOTE: Upon exit of this function the task is guaranteed to be
842  *       released. In particular note that tk_release() will have
843  *       been called, so your task memory may have been freed.
844  */
845 void rpc_execute(struct rpc_task *task)
846 {
847         bool is_async = RPC_IS_ASYNC(task);
848 
849         rpc_set_active(task);
850         rpc_make_runnable(rpciod_workqueue, task);
851         if (!is_async)
852                 __rpc_execute(task);
853 }
854 
855 static void rpc_async_schedule(struct work_struct *work)
856 {
857         __rpc_execute(container_of(work, struct rpc_task, u.tk_work));
858 }
859 
860 /**
861  * rpc_malloc - allocate RPC buffer resources
862  * @task: RPC task
863  *
864  * A single memory region is allocated, which is split between the
865  * RPC call and RPC reply that this task is being used for. When
866  * this RPC is retired, the memory is released by calling rpc_free.
867  *
868  * To prevent rpciod from hanging, this allocator never sleeps,
869  * returning -ENOMEM and suppressing warning if the request cannot
870  * be serviced immediately. The caller can arrange to sleep in a
871  * way that is safe for rpciod.
872  *
873  * Most requests are 'small' (under 2KiB) and can be serviced from a
874  * mempool, ensuring that NFS reads and writes can always proceed,
875  * and that there is good locality of reference for these buffers.
876  *
877  * In order to avoid memory starvation triggering more writebacks of
878  * NFS requests, we avoid using GFP_KERNEL.
879  */
880 int rpc_malloc(struct rpc_task *task)
881 {
882         struct rpc_rqst *rqst = task->tk_rqstp;
883         size_t size = rqst->rq_callsize + rqst->rq_rcvsize;
884         struct rpc_buffer *buf;
885         gfp_t gfp = GFP_NOIO | __GFP_NOWARN;
886 
887         if (RPC_IS_SWAPPER(task))
888                 gfp = __GFP_MEMALLOC | GFP_NOWAIT | __GFP_NOWARN;
889 
890         size += sizeof(struct rpc_buffer);
891         if (size <= RPC_BUFFER_MAXSIZE)
892                 buf = mempool_alloc(rpc_buffer_mempool, gfp);
893         else
894                 buf = kmalloc(size, gfp);
895 
896         if (!buf)
897                 return -ENOMEM;
898 
899         buf->len = size;
900         dprintk("RPC: %5u allocated buffer of size %zu at %p\n",
901                         task->tk_pid, size, buf);
902         rqst->rq_buffer = buf->data;
903         rqst->rq_rbuffer = (char *)rqst->rq_buffer + rqst->rq_callsize;
904         return 0;
905 }
906 EXPORT_SYMBOL_GPL(rpc_malloc);
907 
908 /**
909  * rpc_free - free RPC buffer resources allocated via rpc_malloc
910  * @task: RPC task
911  *
912  */
913 void rpc_free(struct rpc_task *task)
914 {
915         void *buffer = task->tk_rqstp->rq_buffer;
916         size_t size;
917         struct rpc_buffer *buf;
918 
919         buf = container_of(buffer, struct rpc_buffer, data);
920         size = buf->len;
921 
922         dprintk("RPC:       freeing buffer of size %zu at %p\n",
923                         size, buf);
924 
925         if (size <= RPC_BUFFER_MAXSIZE)
926                 mempool_free(buf, rpc_buffer_mempool);
927         else
928                 kfree(buf);
929 }
930 EXPORT_SYMBOL_GPL(rpc_free);
931 
932 /*
933  * Creation and deletion of RPC task structures
934  */
935 static void rpc_init_task(struct rpc_task *task, const struct rpc_task_setup *task_setup_data)
936 {
937         memset(task, 0, sizeof(*task));
938         atomic_set(&task->tk_count, 1);
939         task->tk_flags  = task_setup_data->flags;
940         task->tk_ops = task_setup_data->callback_ops;
941         task->tk_calldata = task_setup_data->callback_data;
942         INIT_LIST_HEAD(&task->tk_task);
943 
944         task->tk_priority = task_setup_data->priority - RPC_PRIORITY_LOW;
945         task->tk_owner = current->tgid;
946 
947         /* Initialize workqueue for async tasks */
948         task->tk_workqueue = task_setup_data->workqueue;
949 
950         task->tk_xprt = xprt_get(task_setup_data->rpc_xprt);
951 
952         if (task->tk_ops->rpc_call_prepare != NULL)
953                 task->tk_action = rpc_prepare_task;
954 
955         rpc_init_task_statistics(task);
956 
957         dprintk("RPC:       new task initialized, procpid %u\n",
958                                 task_pid_nr(current));
959 }
960 
961 static struct rpc_task *
962 rpc_alloc_task(void)
963 {
964         return (struct rpc_task *)mempool_alloc(rpc_task_mempool, GFP_NOIO);
965 }
966 
967 /*
968  * Create a new task for the specified client.
969  */
970 struct rpc_task *rpc_new_task(const struct rpc_task_setup *setup_data)
971 {
972         struct rpc_task *task = setup_data->task;
973         unsigned short flags = 0;
974 
975         if (task == NULL) {
976                 task = rpc_alloc_task();
977                 flags = RPC_TASK_DYNAMIC;
978         }
979 
980         rpc_init_task(task, setup_data);
981         task->tk_flags |= flags;
982         dprintk("RPC:       allocated task %p\n", task);
983         return task;
984 }
985 
986 /*
987  * rpc_free_task - release rpc task and perform cleanups
988  *
989  * Note that we free up the rpc_task _after_ rpc_release_calldata()
990  * in order to work around a workqueue dependency issue.
991  *
992  * Tejun Heo states:
993  * "Workqueue currently considers two work items to be the same if they're
994  * on the same address and won't execute them concurrently - ie. it
995  * makes a work item which is queued again while being executed wait
996  * for the previous execution to complete.
997  *
998  * If a work function frees the work item, and then waits for an event
999  * which should be performed by another work item and *that* work item
1000  * recycles the freed work item, it can create a false dependency loop.
1001  * There really is no reliable way to detect this short of verifying
1002  * every memory free."
1003  *
1004  */
1005 static void rpc_free_task(struct rpc_task *task)
1006 {
1007         unsigned short tk_flags = task->tk_flags;
1008 
1009         rpc_release_calldata(task->tk_ops, task->tk_calldata);
1010 
1011         if (tk_flags & RPC_TASK_DYNAMIC) {
1012                 dprintk("RPC: %5u freeing task\n", task->tk_pid);
1013                 mempool_free(task, rpc_task_mempool);
1014         }
1015 }
1016 
1017 static void rpc_async_release(struct work_struct *work)
1018 {
1019         rpc_free_task(container_of(work, struct rpc_task, u.tk_work));
1020 }
1021 
1022 static void rpc_release_resources_task(struct rpc_task *task)
1023 {
1024         xprt_release(task);
1025         if (task->tk_msg.rpc_cred) {
1026                 put_rpccred(task->tk_msg.rpc_cred);
1027                 task->tk_msg.rpc_cred = NULL;
1028         }
1029         rpc_task_release_client(task);
1030 }
1031 
1032 static void rpc_final_put_task(struct rpc_task *task,
1033                 struct workqueue_struct *q)
1034 {
1035         if (q != NULL) {
1036                 INIT_WORK(&task->u.tk_work, rpc_async_release);
1037                 queue_work(q, &task->u.tk_work);
1038         } else
1039                 rpc_free_task(task);
1040 }
1041 
1042 static void rpc_do_put_task(struct rpc_task *task, struct workqueue_struct *q)
1043 {
1044         if (atomic_dec_and_test(&task->tk_count)) {
1045                 rpc_release_resources_task(task);
1046                 rpc_final_put_task(task, q);
1047         }
1048 }
1049 
1050 void rpc_put_task(struct rpc_task *task)
1051 {
1052         rpc_do_put_task(task, NULL);
1053 }
1054 EXPORT_SYMBOL_GPL(rpc_put_task);
1055 
1056 void rpc_put_task_async(struct rpc_task *task)
1057 {
1058         rpc_do_put_task(task, task->tk_workqueue);
1059 }
1060 EXPORT_SYMBOL_GPL(rpc_put_task_async);
1061 
1062 static void rpc_release_task(struct rpc_task *task)
1063 {
1064         dprintk("RPC: %5u release task\n", task->tk_pid);
1065 
1066         WARN_ON_ONCE(RPC_IS_QUEUED(task));
1067 
1068         rpc_release_resources_task(task);
1069 
1070         /*
1071          * Note: at this point we have been removed from rpc_clnt->cl_tasks,
1072          * so it should be safe to use task->tk_count as a test for whether
1073          * or not any other processes still hold references to our rpc_task.
1074          */
1075         if (atomic_read(&task->tk_count) != 1 + !RPC_IS_ASYNC(task)) {
1076                 /* Wake up anyone who may be waiting for task completion */
1077                 if (!rpc_complete_task(task))
1078                         return;
1079         } else {
1080                 if (!atomic_dec_and_test(&task->tk_count))
1081                         return;
1082         }
1083         rpc_final_put_task(task, task->tk_workqueue);
1084 }
1085 
1086 int rpciod_up(void)
1087 {
1088         return try_module_get(THIS_MODULE) ? 0 : -EINVAL;
1089 }
1090 
1091 void rpciod_down(void)
1092 {
1093         module_put(THIS_MODULE);
1094 }
1095 
1096 /*
1097  * Start up the rpciod workqueue.
1098  */
1099 static int rpciod_start(void)
1100 {
1101         struct workqueue_struct *wq;
1102 
1103         /*
1104          * Create the rpciod thread and wait for it to start.
1105          */
1106         dprintk("RPC:       creating workqueue rpciod\n");
1107         wq = alloc_workqueue("rpciod", WQ_MEM_RECLAIM | WQ_UNBOUND, 0);
1108         if (!wq)
1109                 goto out_failed;
1110         rpciod_workqueue = wq;
1111         /* Note: highpri because network receive is latency sensitive */
1112         wq = alloc_workqueue("xprtiod", WQ_UNBOUND|WQ_MEM_RECLAIM|WQ_HIGHPRI, 0);
1113         if (!wq)
1114                 goto free_rpciod;
1115         xprtiod_workqueue = wq;
1116         return 1;
1117 free_rpciod:
1118         wq = rpciod_workqueue;
1119         rpciod_workqueue = NULL;
1120         destroy_workqueue(wq);
1121 out_failed:
1122         return 0;
1123 }
1124 
1125 static void rpciod_stop(void)
1126 {
1127         struct workqueue_struct *wq = NULL;
1128 
1129         if (rpciod_workqueue == NULL)
1130                 return;
1131         dprintk("RPC:       destroying workqueue rpciod\n");
1132 
1133         wq = rpciod_workqueue;
1134         rpciod_workqueue = NULL;
1135         destroy_workqueue(wq);
1136         wq = xprtiod_workqueue;
1137         xprtiod_workqueue = NULL;
1138         destroy_workqueue(wq);
1139 }
1140 
1141 void
1142 rpc_destroy_mempool(void)
1143 {
1144         rpciod_stop();
1145         mempool_destroy(rpc_buffer_mempool);
1146         mempool_destroy(rpc_task_mempool);
1147         kmem_cache_destroy(rpc_task_slabp);
1148         kmem_cache_destroy(rpc_buffer_slabp);
1149         rpc_destroy_wait_queue(&delay_queue);
1150 }
1151 
1152 int
1153 rpc_init_mempool(void)
1154 {
1155         /*
1156          * The following is not strictly a mempool initialisation,
1157          * but there is no harm in doing it here
1158          */
1159         rpc_init_wait_queue(&delay_queue, "delayq");
1160         if (!rpciod_start())
1161                 goto err_nomem;
1162 
1163         rpc_task_slabp = kmem_cache_create("rpc_tasks",
1164                                              sizeof(struct rpc_task),
1165                                              0, SLAB_HWCACHE_ALIGN,
1166                                              NULL);
1167         if (!rpc_task_slabp)
1168                 goto err_nomem;
1169         rpc_buffer_slabp = kmem_cache_create("rpc_buffers",
1170                                              RPC_BUFFER_MAXSIZE,
1171                                              0, SLAB_HWCACHE_ALIGN,
1172                                              NULL);
1173         if (!rpc_buffer_slabp)
1174                 goto err_nomem;
1175         rpc_task_mempool = mempool_create_slab_pool(RPC_TASK_POOLSIZE,
1176                                                     rpc_task_slabp);
1177         if (!rpc_task_mempool)
1178                 goto err_nomem;
1179         rpc_buffer_mempool = mempool_create_slab_pool(RPC_BUFFER_POOLSIZE,
1180                                                       rpc_buffer_slabp);
1181         if (!rpc_buffer_mempool)
1182                 goto err_nomem;
1183         return 0;
1184 err_nomem:
1185         rpc_destroy_mempool();
1186         return -ENOMEM;
1187 }
1188 

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