kernel/padata.c

   1 /*
   2  * padata.c - generic interface to process data streams in parallel
   3  *
   4  * Copyright (C) 2008, 2009 secunet Security Networks AG
   5  * Copyright (C) 2008, 2009 Steffen Klassert <steffen.klassert@secunet.com>
   6  *
   7  * This program is free software; you can redistribute it and/or modify it
   8  * under the terms and conditions of the GNU General Public License,
   9  * version 2, as published by the Free Software Foundation.
  10  *
  11  * This program is distributed in the hope it will be useful, but WITHOUT
  12  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  13  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
  14  * more details.
  15  *
  16  * You should have received a copy of the GNU General Public License along with
  17  * this program; if not, write to the Free Software Foundation, Inc.,
  18  * 51 Franklin St - Fifth Floor, Boston, MA 02110-1301 USA.
  19  */
  20
  21 #include <linux/module.h>
  22 #include <linux/cpumask.h>
  23 #include <linux/err.h>
  24 #include <linux/cpu.h>
  25 #include <linux/padata.h>
  26 #include <linux/mutex.h>
  27 #include <linux/sched.h>
  28 #include <linux/slab.h>
  29 #include <linux/rcupdate.h>
  30
  31 #define MAX_SEQ_NR INT_MAX - NR_CPUS
  32 #define MAX_OBJ_NUM 1000
  33
  34 static int padata_index_to_cpu(struct parallel_data *pd, int cpu_index)
  35 {
  36         int cpu, target_cpu;
  37
  38         target_cpu = cpumask_first(pd->cpumask);
  39         for (cpu = 0; cpu < cpu_index; cpu++)
  40                 target_cpu = cpumask_next(target_cpu, pd->cpumask);
  41
  42         return target_cpu;
  43 }
  44
  45 static int padata_cpu_hash(struct padata_priv *padata)
  46 {
  47         int cpu_index;
  48         struct parallel_data *pd;
  49
  50         pd =  padata->pd;
  51
  52         /*
  53          * Hash the sequence numbers to the cpus by taking
  54          * seq_nr mod. number of cpus in use.
  55          */
  56         cpu_index =  padata->seq_nr % cpumask_weight(pd->cpumask);
  57
  58         return padata_index_to_cpu(pd, cpu_index);
  59 }
  60
  61 static void padata_parallel_worker(struct work_struct *work)
  62 {
  63         struct padata_queue *queue;
  64         struct parallel_data *pd;
  65         struct padata_instance *pinst;
  66         LIST_HEAD(local_list);
  67
  68         local_bh_disable();
  69         queue = container_of(work, struct padata_queue, pwork);
  70         pd = queue->pd;
  71         pinst = pd->pinst;
  72
  73         spin_lock(&queue->parallel.lock);
  74         list_replace_init(&queue->parallel.list, &local_list);
  75         spin_unlock(&queue->parallel.lock);
  76
  77         while (!list_empty(&local_list)) {
  78                 struct padata_priv *padata;
  79
  80                 padata = list_entry(local_list.next,
  81                                     struct padata_priv, list);
  82
  83                 list_del_init(&padata->list);
  84
  85                 padata->parallel(padata);
  86         }
  87
  88         local_bh_enable();
  89 }
  90
  91 /**
  92  * padata_do_parallel - padata parallelization function
  93  *
  94  * @pinst: padata instance
  95  * @padata: object to be parallelized
  96  * @cb_cpu: cpu the serialization callback function will run on,
  97  *          must be in the cpumask of padata.
  98  *
  99  * The parallelization callback function will run with BHs off.
 100  * Note: Every object which is parallelized by padata_do_parallel
 101  * must be seen by padata_do_serial.
 102  */
 103 int padata_do_parallel(struct padata_instance *pinst,
 104                        struct padata_priv *padata, int cb_cpu)
 105 {
 106         int target_cpu, err;
 107         struct padata_queue *queue;
 108         struct parallel_data *pd;
 109
 110         rcu_read_lock_bh();
 111
 112         pd = rcu_dereference(pinst->pd);
 113
 114         err = 0;
 115         if (!(pinst->flags & PADATA_INIT))
 116                 goto out;
 117
 118         err =  -EBUSY;
 119         if ((pinst->flags & PADATA_RESET))
 120                 goto out;
 121
 122         if (atomic_read(&pd->refcnt) >= MAX_OBJ_NUM)
 123                 goto out;
 124
 125         err = -EINVAL;
 126         if (!cpumask_test_cpu(cb_cpu, pd->cpumask))
 127                 goto out;
 128
 129         err = -EINPROGRESS;
 130         atomic_inc(&pd->refcnt);
 131         padata->pd = pd;
 132         padata->cb_cpu = cb_cpu;
 133
 134         if (unlikely(atomic_read(&pd->seq_nr) == pd->max_seq_nr))
 135                 atomic_set(&pd->seq_nr, -1);
 136
 137         padata->seq_nr = atomic_inc_return(&pd->seq_nr);
 138
 139         target_cpu = padata_cpu_hash(padata);
 140         queue = per_cpu_ptr(pd->queue, target_cpu);
 141
 142         spin_lock(&queue->parallel.lock);
 143         list_add_tail(&padata->list, &queue->parallel.list);
 144         spin_unlock(&queue->parallel.lock);
 145
 146         queue_work_on(target_cpu, pinst->wq, &queue->pwork);
 147
 148 out:
 149         rcu_read_unlock_bh();
 150
 151         return err;
 152 }
 153 EXPORT_SYMBOL(padata_do_parallel);
 154
 155 /*
 156  * padata_get_next - Get the next object that needs serialization.
 157  *
 158  * Return values are:
 159  *
 160  * A pointer to the control struct of the next object that needs
 161  * serialization, if present in one of the percpu reorder queues.
 162  *
 163  * NULL, if all percpu reorder queues are empty.
 164  *
 165  * -EINPROGRESS, if the next object that needs serialization will
 166  *  be parallel processed by another cpu and is not yet present in
 167  *  the cpu's reorder queue.
 168  *
 169  * -ENODATA, if this cpu has to do the parallel processing for
 170  *  the next object.
 171  */
 172 static struct padata_priv *padata_get_next(struct parallel_data *pd)
 173 {
 174         int cpu, num_cpus, empty, calc_seq_nr;
 175         int seq_nr, next_nr, overrun, next_overrun;
 176         struct padata_queue *queue, *next_queue;
 177         struct padata_priv *padata;
 178         struct padata_list *reorder;
 179
 180         empty = 0;
 181         next_nr = -1;
 182         next_overrun = 0;
 183         next_queue = NULL;
 184
 185         num_cpus = cpumask_weight(pd->cpumask);
 186
 187         for_each_cpu(cpu, pd->cpumask) {
 188                 queue = per_cpu_ptr(pd->queue, cpu);
 189                 reorder = &queue->reorder;
 190
 191                 /*
 192                  * Calculate the seq_nr of the object that should be
 193                  * next in this reorder queue.
 194                  */
 195                 overrun = 0;
 196                 calc_seq_nr = (atomic_read(&queue->num_obj) * num_cpus)
 197                                + queue->cpu_index;
 198
 199                 if (unlikely(calc_seq_nr > pd->max_seq_nr)) {
 200                         calc_seq_nr = calc_seq_nr - pd->max_seq_nr - 1;
 201                         overrun = 1;
 202                 }
 203
 204                 if (!list_empty(&reorder->list)) {
 205                         padata = list_entry(reorder->list.next,
 206                                             struct padata_priv, list);
 207
 208                         seq_nr  = padata->seq_nr;
 209                         BUG_ON(calc_seq_nr != seq_nr);
 210                 } else {
 211                         seq_nr = calc_seq_nr;
 212                         empty++;
 213                 }
 214
 215                 if (next_nr < 0 || seq_nr < next_nr
 216                     || (next_overrun && !overrun)) {
 217                         next_nr = seq_nr;
 218                         next_overrun = overrun;
 219                         next_queue = queue;
 220                 }
 221         }
 222
 223         padata = NULL;
 224
 225         if (empty == num_cpus)
 226                 goto out;
 227
 228         reorder = &next_queue->reorder;
 229
 230         if (!list_empty(&reorder->list)) {
 231                 padata = list_entry(reorder->list.next,
 232                                     struct padata_priv, list);
 233
 234                 if (unlikely(next_overrun)) {
 235                         for_each_cpu(cpu, pd->cpumask) {
 236                                 queue = per_cpu_ptr(pd->queue, cpu);
 237                                 atomic_set(&queue->num_obj, 0);
 238                         }
 239                 }
 240
 241                 spin_lock(&reorder->lock);
 242                 list_del_init(&padata->list);
 243                 atomic_dec(&pd->reorder_objects);
 244                 spin_unlock(&reorder->lock);
 245
 246                 atomic_inc(&next_queue->num_obj);
 247
 248                 goto out;
 249         }
 250
 251         queue = per_cpu_ptr(pd->queue, smp_processor_id());
 252         if (queue->cpu_index == next_queue->cpu_index) {
 253                 padata = ERR_PTR(-ENODATA);
 254                 goto out;
 255         }
 256
 257         padata = ERR_PTR(-EINPROGRESS);
 258 out:
 259         return padata;
 260 }
 261
 262 static void padata_reorder(struct parallel_data *pd)
 263 {
 264         struct padata_priv *padata;
 265         struct padata_queue *queue;
 266         struct padata_instance *pinst = pd->pinst;
 267
 268         /*
 269          * We need to ensure that only one cpu can work on dequeueing of
 270          * the reorder queue the time. Calculating in which percpu reorder
 271          * queue the next object will arrive takes some time. A spinlock
 272          * would be highly contended. Also it is not clear in which order
 273          * the objects arrive to the reorder queues. So a cpu could wait to
 274          * get the lock just to notice that there is nothing to do at the
 275          * moment. Therefore we use a trylock and let the holder of the lock
 276          * care for all the objects enqueued during the holdtime of the lock.
 277          */
 278         if (!spin_trylock_bh(&pd->lock))
 279                 return;
 280
 281         while (1) {
 282                 padata = padata_get_next(pd);
 283
 284                 /*
 285                  * All reorder queues are empty, or the next object that needs
 286                  * serialization is parallel processed by another cpu and is
 287                  * still on it's way to the cpu's reorder queue, nothing to
 288                  * do for now.
 289                  */
 290                 if (!padata || PTR_ERR(padata) == -EINPROGRESS)
 291                         break;
 292
 293                 /*
 294                  * This cpu has to do the parallel processing of the next
 295                  * object. It's waiting in the cpu's parallelization queue,
 296                  * so exit imediately.
 297                  */
 298                 if (PTR_ERR(padata) == -ENODATA) {
 299                         del_timer(&pd->timer);
 300                         spin_unlock_bh(&pd->lock);
 301                         return;
 302                 }
 303
 304                 queue = per_cpu_ptr(pd->queue, padata->cb_cpu);
 305
 306                 spin_lock(&queue->serial.lock);
 307                 list_add_tail(&padata->list, &queue->serial.list);
 308                 spin_unlock(&queue->serial.lock);
 309
 310                 queue_work_on(padata->cb_cpu, pinst->wq, &queue->swork);
 311         }
 312
 313         spin_unlock_bh(&pd->lock);
 314
 315         /*
 316          * The next object that needs serialization might have arrived to
 317          * the reorder queues in the meantime, we will be called again
 318          * from the timer function if noone else cares for it.
 319          */
 320         if (atomic_read(&pd->reorder_objects)
 321                         && !(pinst->flags & PADATA_RESET))
 322                 mod_timer(&pd->timer, jiffies + HZ);
 323         else
 324                 del_timer(&pd->timer);
 325
 326         return;
 327 }
 328
 329 static void padata_reorder_timer(unsigned long arg)
 330 {
 331         struct parallel_data *pd = (struct parallel_data *)arg;
 332
 333         padata_reorder(pd);
 334 }
 335
 336 static void padata_serial_worker(struct work_struct *work)
 337 {
 338         struct padata_queue *queue;
 339         struct parallel_data *pd;
 340         LIST_HEAD(local_list);
 341
 342         local_bh_disable();
 343         queue = container_of(work, struct padata_queue, swork);
 344         pd = queue->pd;
 345
 346         spin_lock(&queue->serial.lock);
 347         list_replace_init(&queue->serial.list, &local_list);
 348         spin_unlock(&queue->serial.lock);
 349
 350         while (!list_empty(&local_list)) {
 351                 struct padata_priv *padata;
 352
 353                 padata = list_entry(local_list.next,
 354                                     struct padata_priv, list);
 355
 356                 list_del_init(&padata->list);
 357
 358                 padata->serial(padata);
 359                 atomic_dec(&pd->refcnt);
 360         }
 361         local_bh_enable();
 362 }
 363
 364 /**
 365  * padata_do_serial - padata serialization function
 366  *
 367  * @padata: object to be serialized.
 368  *
 369  * padata_do_serial must be called for every parallelized object.
 370  * The serialization callback function will run with BHs off.
 371  */
 372 void padata_do_serial(struct padata_priv *padata)
 373 {
 374         int cpu;
 375         struct padata_queue *queue;
 376         struct parallel_data *pd;
 377
 378         pd = padata->pd;
 379
 380         cpu = get_cpu();
 381         queue = per_cpu_ptr(pd->queue, cpu);
 382
 383         spin_lock(&queue->reorder.lock);
 384         atomic_inc(&pd->reorder_objects);
 385         list_add_tail(&padata->list, &queue->reorder.list);
 386         spin_unlock(&queue->reorder.lock);
 387
 388         put_cpu();
 389
 390         padata_reorder(pd);
 391 }
 392 EXPORT_SYMBOL(padata_do_serial);
 393
 394 /* Allocate and initialize the internal cpumask dependend resources. */
 395 static struct parallel_data *padata_alloc_pd(struct padata_instance *pinst,
 396                                              const struct cpumask *cpumask)
 397 {
 398         int cpu, cpu_index, num_cpus;
 399         struct padata_queue *queue;
 400         struct parallel_data *pd;
 401
 402         cpu_index = 0;
 403
 404         pd = kzalloc(sizeof(struct parallel_data), GFP_KERNEL);
 405         if (!pd)
 406                 goto err;
 407
 408         pd->queue = alloc_percpu(struct padata_queue);
 409         if (!pd->queue)
 410                 goto err_free_pd;
 411
 412         if (!alloc_cpumask_var(&pd->cpumask, GFP_KERNEL))
 413                 goto err_free_queue;
 414
 415         cpumask_and(pd->cpumask, cpumask, cpu_active_mask);
 416
 417         for_each_cpu(cpu, pd->cpumask) {
 418                 queue = per_cpu_ptr(pd->queue, cpu);
 419
 420                 queue->pd = pd;
 421
 422                 queue->cpu_index = cpu_index;
 423                 cpu_index++;
 424
 425                 INIT_LIST_HEAD(&queue->reorder.list);
 426                 INIT_LIST_HEAD(&queue->parallel.list);
 427                 INIT_LIST_HEAD(&queue->serial.list);
 428                 spin_lock_init(&queue->reorder.lock);
 429                 spin_lock_init(&queue->parallel.lock);
 430                 spin_lock_init(&queue->serial.lock);
 431
 432                 INIT_WORK(&queue->pwork, padata_parallel_worker);
 433                 INIT_WORK(&queue->swork, padata_serial_worker);
 434                 atomic_set(&queue->num_obj, 0);
 435         }
 436
 437         num_cpus = cpumask_weight(pd->cpumask);
 438         pd->max_seq_nr = (MAX_SEQ_NR / num_cpus) * num_cpus - 1;
 439
 440         setup_timer(&pd->timer, padata_reorder_timer, (unsigned long)pd);
 441         atomic_set(&pd->seq_nr, -1);
 442         atomic_set(&pd->reorder_objects, 0);
 443         atomic_set(&pd->refcnt, 0);
 444         pd->pinst = pinst;
 445         spin_lock_init(&pd->lock);
 446
 447         return pd;
 448
 449 err_free_queue:
 450         free_percpu(pd->queue);
 451 err_free_pd:
 452         kfree(pd);
 453 err:
 454         return NULL;
 455 }
 456
 457 static void padata_free_pd(struct parallel_data *pd)
 458 {
 459         free_cpumask_var(pd->cpumask);
 460         free_percpu(pd->queue);
 461         kfree(pd);
 462 }
 463
 464 /* Flush all objects out of the padata queues. */
 465 static void padata_flush_queues(struct parallel_data *pd)
 466 {
 467         int cpu;
 468         struct padata_queue *queue;
 469
 470         for_each_cpu(cpu, pd->cpumask) {
 471                 queue = per_cpu_ptr(pd->queue, cpu);
 472                 flush_work(&queue->pwork);
 473         }
 474
 475         del_timer_sync(&pd->timer);
 476
 477         if (atomic_read(&pd->reorder_objects))
 478                 padata_reorder(pd);
 479
 480         for_each_cpu(cpu, pd->cpumask) {
 481                 queue = per_cpu_ptr(pd->queue, cpu);
 482                 flush_work(&queue->swork);
 483         }
 484
 485         BUG_ON(atomic_read(&pd->refcnt) != 0);
 486 }
 487
 488 /* Replace the internal control stucture with a new one. */
 489 static void padata_replace(struct padata_instance *pinst,
 490                            struct parallel_data *pd_new)
 491 {
 492         struct parallel_data *pd_old = pinst->pd;
 493
 494         pinst->flags |= PADATA_RESET;
 495
 496         rcu_assign_pointer(pinst->pd, pd_new);
 497
 498         synchronize_rcu();
 499
 500         padata_flush_queues(pd_old);
 501         padata_free_pd(pd_old);
 502
 503         pinst->flags &= ~PADATA_RESET;
 504 }
 505
 506 /**
 507  * padata_set_cpumask - set the cpumask that padata should use
 508  *
 509  * @pinst: padata instance
 510  * @cpumask: the cpumask to use
 511  */
 512 int padata_set_cpumask(struct padata_instance *pinst,
 513                         cpumask_var_t cpumask)
 514 {
 515         struct parallel_data *pd;
 516         int err = 0;
 517
 518         mutex_lock(&pinst->lock);
 519
 520         get_online_cpus();
 521
 522         pd = padata_alloc_pd(pinst, cpumask);
 523         if (!pd) {
 524                 err = -ENOMEM;
 525                 goto out;
 526         }
 527
 528         cpumask_copy(pinst->cpumask, cpumask);
 529
 530         padata_replace(pinst, pd);
 531
 532 out:
 533         put_online_cpus();
 534
 535         mutex_unlock(&pinst->lock);
 536
 537         return err;
 538 }
 539 EXPORT_SYMBOL(padata_set_cpumask);
 540
 541 static int __padata_add_cpu(struct padata_instance *pinst, int cpu)
 542 {
 543         struct parallel_data *pd;
 544
 545         if (cpumask_test_cpu(cpu, cpu_active_mask)) {
 546                 pd = padata_alloc_pd(pinst, pinst->cpumask);
 547                 if (!pd)
 548                         return -ENOMEM;
 549
 550                 padata_replace(pinst, pd);
 551         }
 552
 553         return 0;
 554 }
 555
 556 /**
 557  * padata_add_cpu - add a cpu to the padata cpumask
 558  *
 559  * @pinst: padata instance
 560  * @cpu: cpu to add
 561  */
 562 int padata_add_cpu(struct padata_instance *pinst, int cpu)
 563 {
 564         int err;
 565
 566         mutex_lock(&pinst->lock);
 567
 568         get_online_cpus();
 569         cpumask_set_cpu(cpu, pinst->cpumask);
 570         err = __padata_add_cpu(pinst, cpu);
 571         put_online_cpus();
 572
 573         mutex_unlock(&pinst->lock);
 574
 575         return err;
 576 }
 577 EXPORT_SYMBOL(padata_add_cpu);
 578
 579 static int __padata_remove_cpu(struct padata_instance *pinst, int cpu)
 580 {
 581         struct parallel_data *pd;
 582
 583         if (cpumask_test_cpu(cpu, cpu_online_mask)) {
 584                 pd = padata_alloc_pd(pinst, pinst->cpumask);
 585                 if (!pd)
 586                         return -ENOMEM;
 587
 588                 padata_replace(pinst, pd);
 589         }
 590
 591         return 0;
 592 }
 593
 594 /**
 595  * padata_remove_cpu - remove a cpu from the padata cpumask
 596  *
 597  * @pinst: padata instance
 598  * @cpu: cpu to remove
 599  */
 600 int padata_remove_cpu(struct padata_instance *pinst, int cpu)
 601 {
 602         int err;
 603
 604         mutex_lock(&pinst->lock);
 605
 606         get_online_cpus();
 607         cpumask_clear_cpu(cpu, pinst->cpumask);
 608         err = __padata_remove_cpu(pinst, cpu);
 609         put_online_cpus();
 610
 611         mutex_unlock(&pinst->lock);
 612
 613         return err;
 614 }
 615 EXPORT_SYMBOL(padata_remove_cpu);
 616
 617 /**
 618  * padata_start - start the parallel processing
 619  *
 620  * @pinst: padata instance to start
 621  */
 622 void padata_start(struct padata_instance *pinst)
 623 {
 624         mutex_lock(&pinst->lock);
 625         pinst->flags |= PADATA_INIT;
 626         mutex_unlock(&pinst->lock);
 627 }
 628 EXPORT_SYMBOL(padata_start);
 629
 630 /**
 631  * padata_stop - stop the parallel processing
 632  *
 633  * @pinst: padata instance to stop
 634  */
 635 void padata_stop(struct padata_instance *pinst)
 636 {
 637         mutex_lock(&pinst->lock);
 638         pinst->flags &= ~PADATA_INIT;
 639         mutex_unlock(&pinst->lock);
 640 }
 641 EXPORT_SYMBOL(padata_stop);
 642
 643 #ifdef CONFIG_HOTPLUG_CPU
 644 static int padata_cpu_callback(struct notifier_block *nfb,
 645                                unsigned long action, void *hcpu)
 646 {
 647         int err;
 648         struct padata_instance *pinst;
 649         int cpu = (unsigned long)hcpu;
 650
 651         pinst = container_of(nfb, struct padata_instance, cpu_notifier);
 652
 653         switch (action) {
 654         case CPU_ONLINE:
 655         case CPU_ONLINE_FROZEN:
 656                 if (!cpumask_test_cpu(cpu, pinst->cpumask))
 657                         break;
 658                 mutex_lock(&pinst->lock);
 659                 err = __padata_add_cpu(pinst, cpu);
 660                 mutex_unlock(&pinst->lock);
 661                 if (err)
 662                         return notifier_from_errno(err);
 663                 break;
 664
 665         case CPU_DOWN_PREPARE:
 666         case CPU_DOWN_PREPARE_FROZEN:
 667                 if (!cpumask_test_cpu(cpu, pinst->cpumask))
 668                         break;
 669                 mutex_lock(&pinst->lock);
 670                 err = __padata_remove_cpu(pinst, cpu);
 671                 mutex_unlock(&pinst->lock);
 672                 if (err)
 673                         return notifier_from_errno(err);
 674                 break;
 675
 676         case CPU_UP_CANCELED:
 677         case CPU_UP_CANCELED_FROZEN:
 678                 if (!cpumask_test_cpu(cpu, pinst->cpumask))
 679                         break;
 680                 mutex_lock(&pinst->lock);
 681                 __padata_remove_cpu(pinst, cpu);
 682                 mutex_unlock(&pinst->lock);
 683
 684         case CPU_DOWN_FAILED:
 685         case CPU_DOWN_FAILED_FROZEN:
 686                 if (!cpumask_test_cpu(cpu, pinst->cpumask))
 687                         break;
 688                 mutex_lock(&pinst->lock);
 689                 __padata_add_cpu(pinst, cpu);
 690                 mutex_unlock(&pinst->lock);
 691         }
 692
 693         return NOTIFY_OK;
 694 }
 695 #endif
 696
 697 /**
 698  * padata_alloc - allocate and initialize a padata instance
 699  *
 700  * @cpumask: cpumask that padata uses for parallelization
 701  * @wq: workqueue to use for the allocated padata instance
 702  */
 703 struct padata_instance *padata_alloc(const struct cpumask *cpumask,
 704                                      struct workqueue_struct *wq)
 705 {
 706         struct padata_instance *pinst;
 707         struct parallel_data *pd;
 708
 709         pinst = kzalloc(sizeof(struct padata_instance), GFP_KERNEL);
 710         if (!pinst)
 711                 goto err;
 712
 713         get_online_cpus();
 714
 715         pd = padata_alloc_pd(pinst, cpumask);
 716         if (!pd)
 717                 goto err_free_inst;
 718
 719         if (!alloc_cpumask_var(&pinst->cpumask, GFP_KERNEL))
 720                 goto err_free_pd;
 721
 722         rcu_assign_pointer(pinst->pd, pd);
 723
 724         pinst->wq = wq;
 725
 726         cpumask_copy(pinst->cpumask, cpumask);
 727
 728         pinst->flags = 0;
 729
 730 #ifdef CONFIG_HOTPLUG_CPU
 731         pinst->cpu_notifier.notifier_call = padata_cpu_callback;
 732         pinst->cpu_notifier.priority = 0;
 733         register_hotcpu_notifier(&pinst->cpu_notifier);
 734 #endif
 735
 736         put_online_cpus();
 737
 738         mutex_init(&pinst->lock);
 739
 740         return pinst;
 741
 742 err_free_pd:
 743         padata_free_pd(pd);
 744 err_free_inst:
 745         kfree(pinst);
 746         put_online_cpus();
 747 err:
 748         return NULL;
 749 }
 750 EXPORT_SYMBOL(padata_alloc);
 751
 752 /**
 753  * padata_free - free a padata instance
 754  *
 755  * @padata_inst: padata instance to free
 756  */
 757 void padata_free(struct padata_instance *pinst)
 758 {
 759         padata_stop(pinst);
 760
 761         synchronize_rcu();
 762
 763 #ifdef CONFIG_HOTPLUG_CPU
 764         unregister_hotcpu_notifier(&pinst->cpu_notifier);
 765 #endif
 766         get_online_cpus();
 767         padata_flush_queues(pinst->pd);
 768         put_online_cpus();
 769
 770         padata_free_pd(pinst->pd);
 771         free_cpumask_var(pinst->cpumask);
 772         kfree(pinst);
 773 }
 774 EXPORT_SYMBOL(padata_free);