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 static void __padata_start(struct padata_instance *pinst)
 489 {
 490         pinst->flags |= PADATA_INIT;
 491 }
 492
 493 static void __padata_stop(struct padata_instance *pinst)
 494 {
 495         if (!(pinst->flags & PADATA_INIT))
 496                 return;
 497
 498         pinst->flags &= ~PADATA_INIT;
 499
 500         synchronize_rcu();
 501
 502         get_online_cpus();
 503         padata_flush_queues(pinst->pd);
 504         put_online_cpus();
 505 }
 506
 507 /* Replace the internal control stucture with a new one. */
 508 static void padata_replace(struct padata_instance *pinst,
 509                            struct parallel_data *pd_new)
 510 {
 511         struct parallel_data *pd_old = pinst->pd;
 512
 513         pinst->flags |= PADATA_RESET;
 514
 515         rcu_assign_pointer(pinst->pd, pd_new);
 516
 517         synchronize_rcu();
 518
 519         padata_flush_queues(pd_old);
 520         padata_free_pd(pd_old);
 521
 522         pinst->flags &= ~PADATA_RESET;
 523 }
 524
 525 /**
 526  * padata_set_cpumask - set the cpumask that padata should use
 527  *
 528  * @pinst: padata instance
 529  * @cpumask: the cpumask to use
 530  */
 531 int padata_set_cpumask(struct padata_instance *pinst,
 532                         cpumask_var_t cpumask)
 533 {
 534         struct parallel_data *pd;
 535         int err = 0;
 536
 537         mutex_lock(&pinst->lock);
 538
 539         get_online_cpus();
 540
 541         pd = padata_alloc_pd(pinst, cpumask);
 542         if (!pd) {
 543                 err = -ENOMEM;
 544                 goto out;
 545         }
 546
 547         cpumask_copy(pinst->cpumask, cpumask);
 548
 549         padata_replace(pinst, pd);
 550
 551 out:
 552         put_online_cpus();
 553
 554         mutex_unlock(&pinst->lock);
 555
 556         return err;
 557 }
 558 EXPORT_SYMBOL(padata_set_cpumask);
 559
 560 static int __padata_add_cpu(struct padata_instance *pinst, int cpu)
 561 {
 562         struct parallel_data *pd;
 563
 564         if (cpumask_test_cpu(cpu, cpu_active_mask)) {
 565                 pd = padata_alloc_pd(pinst, pinst->cpumask);
 566                 if (!pd)
 567                         return -ENOMEM;
 568
 569                 padata_replace(pinst, pd);
 570         }
 571
 572         return 0;
 573 }
 574
 575 /**
 576  * padata_add_cpu - add a cpu to the padata cpumask
 577  *
 578  * @pinst: padata instance
 579  * @cpu: cpu to add
 580  */
 581 int padata_add_cpu(struct padata_instance *pinst, int cpu)
 582 {
 583         int err;
 584
 585         mutex_lock(&pinst->lock);
 586
 587         get_online_cpus();
 588         cpumask_set_cpu(cpu, pinst->cpumask);
 589         err = __padata_add_cpu(pinst, cpu);
 590         put_online_cpus();
 591
 592         mutex_unlock(&pinst->lock);
 593
 594         return err;
 595 }
 596 EXPORT_SYMBOL(padata_add_cpu);
 597
 598 static int __padata_remove_cpu(struct padata_instance *pinst, int cpu)
 599 {
 600         struct parallel_data *pd;
 601
 602         if (cpumask_test_cpu(cpu, cpu_online_mask)) {
 603                 pd = padata_alloc_pd(pinst, pinst->cpumask);
 604                 if (!pd)
 605                         return -ENOMEM;
 606
 607                 padata_replace(pinst, pd);
 608         }
 609
 610         return 0;
 611 }
 612
 613 /**
 614  * padata_remove_cpu - remove a cpu from the padata cpumask
 615  *
 616  * @pinst: padata instance
 617  * @cpu: cpu to remove
 618  */
 619 int padata_remove_cpu(struct padata_instance *pinst, int cpu)
 620 {
 621         int err;
 622
 623         mutex_lock(&pinst->lock);
 624
 625         get_online_cpus();
 626         cpumask_clear_cpu(cpu, pinst->cpumask);
 627         err = __padata_remove_cpu(pinst, cpu);
 628         put_online_cpus();
 629
 630         mutex_unlock(&pinst->lock);
 631
 632         return err;
 633 }
 634 EXPORT_SYMBOL(padata_remove_cpu);
 635
 636 /**
 637  * padata_start - start the parallel processing
 638  *
 639  * @pinst: padata instance to start
 640  */
 641 int padata_start(struct padata_instance *pinst)
 642 {
 643         int err = 0;
 644
 645         mutex_lock(&pinst->lock);
 646
 647         if (pinst->flags & PADATA_INVALID)
 648                 err =-EINVAL;
 649
 650          __padata_start(pinst);
 651
 652         mutex_unlock(&pinst->lock);
 653
 654         return err;
 655 }
 656 EXPORT_SYMBOL(padata_start);
 657
 658 /**
 659  * padata_stop - stop the parallel processing
 660  *
 661  * @pinst: padata instance to stop
 662  */
 663 void padata_stop(struct padata_instance *pinst)
 664 {
 665         mutex_lock(&pinst->lock);
 666         __padata_stop(pinst);
 667         mutex_unlock(&pinst->lock);
 668 }
 669 EXPORT_SYMBOL(padata_stop);
 670
 671 #ifdef CONFIG_HOTPLUG_CPU
 672 static int padata_cpu_callback(struct notifier_block *nfb,
 673                                unsigned long action, void *hcpu)
 674 {
 675         int err;
 676         struct padata_instance *pinst;
 677         int cpu = (unsigned long)hcpu;
 678
 679         pinst = container_of(nfb, struct padata_instance, cpu_notifier);
 680
 681         switch (action) {
 682         case CPU_ONLINE:
 683         case CPU_ONLINE_FROZEN:
 684                 if (!cpumask_test_cpu(cpu, pinst->cpumask))
 685                         break;
 686                 mutex_lock(&pinst->lock);
 687                 err = __padata_add_cpu(pinst, cpu);
 688                 mutex_unlock(&pinst->lock);
 689                 if (err)
 690                         return NOTIFY_BAD;
 691                 break;
 692
 693         case CPU_DOWN_PREPARE:
 694         case CPU_DOWN_PREPARE_FROZEN:
 695                 if (!cpumask_test_cpu(cpu, pinst->cpumask))
 696                         break;
 697                 mutex_lock(&pinst->lock);
 698                 err = __padata_remove_cpu(pinst, cpu);
 699                 mutex_unlock(&pinst->lock);
 700                 if (err)
 701                         return NOTIFY_BAD;
 702                 break;
 703
 704         case CPU_UP_CANCELED:
 705         case CPU_UP_CANCELED_FROZEN:
 706                 if (!cpumask_test_cpu(cpu, pinst->cpumask))
 707                         break;
 708                 mutex_lock(&pinst->lock);
 709                 __padata_remove_cpu(pinst, cpu);
 710                 mutex_unlock(&pinst->lock);
 711
 712         case CPU_DOWN_FAILED:
 713         case CPU_DOWN_FAILED_FROZEN:
 714                 if (!cpumask_test_cpu(cpu, pinst->cpumask))
 715                         break;
 716                 mutex_lock(&pinst->lock);
 717                 __padata_add_cpu(pinst, cpu);
 718                 mutex_unlock(&pinst->lock);
 719         }
 720
 721         return NOTIFY_OK;
 722 }
 723 #endif
 724
 725 /**
 726  * padata_alloc - allocate and initialize a padata instance
 727  *
 728  * @cpumask: cpumask that padata uses for parallelization
 729  * @wq: workqueue to use for the allocated padata instance
 730  */
 731 struct padata_instance *padata_alloc(const struct cpumask *cpumask,
 732                                      struct workqueue_struct *wq)
 733 {
 734         struct padata_instance *pinst;
 735         struct parallel_data *pd;
 736
 737         pinst = kzalloc(sizeof(struct padata_instance), GFP_KERNEL);
 738         if (!pinst)
 739                 goto err;
 740
 741         get_online_cpus();
 742
 743         pd = padata_alloc_pd(pinst, cpumask);
 744         if (!pd)
 745                 goto err_free_inst;
 746
 747         if (!alloc_cpumask_var(&pinst->cpumask, GFP_KERNEL))
 748                 goto err_free_pd;
 749
 750         rcu_assign_pointer(pinst->pd, pd);
 751
 752         pinst->wq = wq;
 753
 754         cpumask_copy(pinst->cpumask, cpumask);
 755
 756         pinst->flags = 0;
 757
 758 #ifdef CONFIG_HOTPLUG_CPU
 759         pinst->cpu_notifier.notifier_call = padata_cpu_callback;
 760         pinst->cpu_notifier.priority = 0;
 761         register_hotcpu_notifier(&pinst->cpu_notifier);
 762 #endif
 763
 764         put_online_cpus();
 765
 766         mutex_init(&pinst->lock);
 767
 768         return pinst;
 769
 770 err_free_pd:
 771         padata_free_pd(pd);
 772 err_free_inst:
 773         kfree(pinst);
 774         put_online_cpus();
 775 err:
 776         return NULL;
 777 }
 778 EXPORT_SYMBOL(padata_alloc);
 779
 780 /**
 781  * padata_free - free a padata instance
 782  *
 783  * @padata_inst: padata instance to free
 784  */
 785 void padata_free(struct padata_instance *pinst)
 786 {
 787 #ifdef CONFIG_HOTPLUG_CPU
 788         unregister_hotcpu_notifier(&pinst->cpu_notifier);
 789 #endif
 790
 791         padata_stop(pinst);
 792         padata_free_pd(pinst->pd);
 793         free_cpumask_var(pinst->cpumask);
 794         kfree(pinst);
 795 }
 796 EXPORT_SYMBOL(padata_free);