kernel/pwqr.c

   1 /*
   2  * Copyright (C) 2012   Pierre Habouzit <pierre.habouzit@intersec.com>
   3  * Copyright (C) 2012   Intersec SAS
   4  *
   5  * This file implements the Linux Pthread Workqueue Regulator, and is part
   6  * of the linux kernel.
   7  *
   8  * The Linux Kernel is free software: you can redistribute it and/or modify it
   9  * under the terms of the GNU General Public License version 2 as published by
  10  * the Free Software Foundation.
  11  *
  12  * The Linux Kernel is distributed in the hope that it will be useful, but
  13  * WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
  14  * or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU Lesser General Public
  15  * License for more details.
  16  *
  17  * You should have received a copy of the GNU General Public License version 2
  18  * along with The Linux Kernel.  If not, see <http://www.gnu.org/licenses/>.
  19  */
  20
  21 #include <linux/cdev.h>
  22 #include <linux/device.h>
  23 #include <linux/file.h>
  24 #include <linux/fs.h>
  25 #include <linux/hash.h>
  26 #include <linux/init.h>
  27 #include <linux/kref.h>
  28 #include <linux/module.h>
  29 #include <linux/sched.h>
  30 #include <linux/slab.h>
  31 #include <linux/spinlock.h>
  32 #include <linux/timer.h>
  33 #include <linux/uaccess.h>
  34 #include <linux/wait.h>
  35
  36 #ifndef CONFIG_PREEMPT_NOTIFIERS
  37 #  error PWQ module requires CONFIG_PREEMPT_NOTIFIERS
  38 #endif
  39
  40 #include "pwqr.h"
  41
  42 #define PWQR_HASH_BITS          5
  43 #define PWQR_HASH_SIZE          (1 << PWQR_HASH_BITS)
  44
  45 #define PWQR_UC_DELAY           (HZ / 10)
  46 #define PWQR_OC_DELAY           (HZ / 20)
  47
  48 #define PWQR_STATE_NONE         0
  49 #define PWQR_STATE_UC           1
  50 #define PWQR_STATE_OC           2
  51 #define PWQR_STATE_DEAD         (-1)
  52
  53 struct pwqr_task_bucket {
  54         spinlock_t              lock;
  55         struct hlist_head       tasks;
  56 };
  57
  58 struct pwqr_sb {
  59         struct kref             kref;
  60         struct rcu_head         rcu;
  61         struct timer_list       timer;
  62         wait_queue_head_t       wqh;
  63
  64         unsigned                concurrency;
  65         unsigned                registered;
  66
  67         unsigned                running;
  68         unsigned                waiting;
  69         unsigned                parked;
  70         unsigned                overcommit_wakes;
  71
  72         int                     state;
  73 };
  74
  75 struct pwqr_task {
  76         struct preempt_notifier notifier;
  77         struct hlist_node       link;
  78         struct rcu_head         rcu;
  79         struct task_struct     *task;
  80         struct pwqr_sb         *sb;
  81 };
  82
  83 /*
  84  * Global variables
  85  */
  86 static struct class            *pwqr_class;
  87 static int                      pwqr_major;
  88 static struct pwqr_task_bucket  pwqr_tasks_hash[PWQR_HASH_SIZE];
  89 static struct preempt_ops       pwqr_preempt_running_ops;
  90 static struct preempt_ops       pwqr_preempt_blocked_ops;
  91 static struct preempt_ops       pwqr_preempt_noop_ops;
  92
  93 /*****************************************************************************
  94  * Scoreboards
  95  */
  96
  97 #define pwqr_sb_lock_irqsave(sb, flags) \
  98         spin_lock_irqsave(&(sb)->wqh.lock, flags)
  99 #define pwqr_sb_unlock_irqrestore(sb, flags) \
 100         spin_unlock_irqrestore(&(sb)->wqh.lock, flags)
 101
 102 static inline void pwqr_arm_timer(struct pwqr_sb *sb, int how, int delay)
 103 {
 104         if (timer_pending(&sb->timer) && sb->state == how)
 105                 return;
 106         mod_timer(&sb->timer, jiffies + delay);
 107         sb->state = how;
 108 }
 109
 110 static inline void __pwqr_sb_update_state(struct pwqr_sb *sb, int running_delta)
 111 {
 112         sb->running += running_delta;
 113
 114         if (sb->running < sb->concurrency && sb->waiting == 0 && sb->parked) {
 115                 pwqr_arm_timer(sb, PWQR_STATE_UC, PWQR_UC_DELAY);
 116         } else if (sb->running > sb->concurrency) {
 117                 pwqr_arm_timer(sb, PWQR_STATE_OC, PWQR_OC_DELAY);
 118         } else {
 119                 sb->state = PWQR_STATE_NONE;
 120                 if (!timer_pending(&sb->timer))
 121                         del_timer(&sb->timer);
 122         }
 123 }
 124
 125 static void pwqr_sb_timer_cb(unsigned long arg)
 126 {
 127         struct pwqr_sb *sb = (struct pwqr_sb *)arg;
 128         unsigned long flags;
 129
 130         pwqr_sb_lock_irqsave(sb, flags);
 131         if (sb->running < sb->concurrency && sb->waiting == 0 && sb->parked) {
 132                 if (sb->overcommit_wakes == 0)
 133                         wake_up_locked(&sb->wqh);
 134         }
 135         if (sb->running > sb->concurrency) {
 136                 /* See ../Documentation/pwqr.adoc */
 137         }
 138         pwqr_sb_unlock_irqrestore(sb, flags);
 139 }
 140
 141 static struct pwqr_sb *pwqr_sb_create(void)
 142 {
 143         struct pwqr_sb *sb;
 144
 145         sb = kzalloc(sizeof(struct pwqr_sb), GFP_KERNEL);
 146         if (sb == NULL)
 147                 return ERR_PTR(-ENOMEM);
 148
 149         kref_init(&sb->kref);
 150         init_waitqueue_head(&sb->wqh);
 151         sb->concurrency    = num_online_cpus();
 152         init_timer(&sb->timer);
 153         sb->timer.function = pwqr_sb_timer_cb;
 154         sb->timer.data     = (unsigned long)sb;
 155
 156         __module_get(THIS_MODULE);
 157         return sb;
 158 }
 159 static inline void pwqr_sb_get(struct pwqr_sb *sb)
 160 {
 161         kref_get(&sb->kref);
 162 }
 163
 164 static void pwqr_sb_finalize(struct rcu_head *rcu)
 165 {
 166         struct pwqr_sb *sb = container_of(rcu, struct pwqr_sb, rcu);
 167
 168         module_put(THIS_MODULE);
 169         kfree(sb);
 170 }
 171
 172 static void pwqr_sb_release(struct kref *kref)
 173 {
 174         struct pwqr_sb *sb = container_of(kref, struct pwqr_sb, kref);
 175
 176         del_timer_sync(&sb->timer);
 177         call_rcu(&sb->rcu, pwqr_sb_finalize);
 178 }
 179 static inline void pwqr_sb_put(struct pwqr_sb *sb)
 180 {
 181         kref_put(&sb->kref, pwqr_sb_release);
 182 }
 183
 184 /*****************************************************************************
 185  * tasks
 186  */
 187 static inline struct pwqr_task_bucket *task_hbucket(struct task_struct *task)
 188 {
 189         return &pwqr_tasks_hash[hash_ptr(task, PWQR_HASH_BITS)];
 190 }
 191
 192 static struct pwqr_task *pwqr_task_find(struct task_struct *task)
 193 {
 194         struct pwqr_task_bucket *b = task_hbucket(task);
 195         struct hlist_node *node;
 196         struct pwqr_task *pwqt = NULL;
 197
 198         spin_lock(&b->lock);
 199         hlist_for_each_entry(pwqt, node, &b->tasks, link) {
 200                 if (pwqt->task == task)
 201                         break;
 202         }
 203         spin_unlock(&b->lock);
 204         return pwqt;
 205 }
 206
 207 static struct pwqr_task *pwqr_task_create(struct task_struct *task)
 208 {
 209         struct pwqr_task_bucket *b = task_hbucket(task);
 210         struct pwqr_task *pwqt;
 211
 212         pwqt = kmalloc(sizeof(*pwqt), GFP_KERNEL);
 213         if (pwqt == NULL)
 214                 return ERR_PTR(-ENOMEM);
 215
 216         preempt_notifier_init(&pwqt->notifier, &pwqr_preempt_running_ops);
 217         preempt_notifier_register(&pwqt->notifier);
 218         pwqt->task = task;
 219
 220         spin_lock(&b->lock);
 221         hlist_add_head(&pwqt->link, &b->tasks);
 222         spin_unlock(&b->lock);
 223
 224         return pwqt;
 225 }
 226
 227 __cold
 228 static void pwqr_task_detach(struct pwqr_task *pwqt, struct pwqr_sb *sb)
 229 {
 230         unsigned long flags;
 231
 232         pwqr_sb_lock_irqsave(sb, flags);
 233         sb->registered--;
 234         if (pwqt->notifier.ops == &pwqr_preempt_running_ops) {
 235                 __pwqr_sb_update_state(sb, -1);
 236         } else {
 237                 __pwqr_sb_update_state(sb, 0);
 238         }
 239         pwqr_sb_unlock_irqrestore(sb, flags);
 240         pwqr_sb_put(sb);
 241         pwqt->sb = NULL;
 242 }
 243
 244 __cold
 245 static void pwqr_task_attach(struct pwqr_task *pwqt, struct pwqr_sb *sb)
 246 {
 247         unsigned long flags;
 248
 249         pwqr_sb_lock_irqsave(sb, flags);
 250         pwqr_sb_get(pwqt->sb = sb);
 251         sb->registered++;
 252         __pwqr_sb_update_state(sb, 1);
 253         pwqr_sb_unlock_irqrestore(sb, flags);
 254 }
 255
 256 __cold
 257 static void pwqr_task_release(struct pwqr_task *pwqt, bool from_notifier)
 258 {
 259         struct pwqr_task_bucket *b = task_hbucket(pwqt->task);
 260
 261         spin_lock(&b->lock);
 262         hlist_del(&pwqt->link);
 263         spin_unlock(&b->lock);
 264         pwqt->notifier.ops = &pwqr_preempt_noop_ops;
 265
 266         if (from_notifier) {
 267                 /* When called from sched_{out,in}, it's not allowed to
 268                  * call preempt_notifier_unregister (or worse kfree())
 269                  *
 270                  * Though it's not a good idea to kfree() still registered
 271                  * callbacks if we're not dying, it'll panic on the next
 272                  * sched_{in,out} call.
 273                  */
 274                 BUG_ON(!(pwqt->task->state & TASK_DEAD));
 275                 kfree_rcu(pwqt, rcu);
 276         } else {
 277                 preempt_notifier_unregister(&pwqt->notifier);
 278                 kfree(pwqt);
 279         }
 280 }
 281
 282 static void pwqr_task_noop_sched_in(struct preempt_notifier *notifier, int cpu)
 283 {
 284 }
 285
 286 static void pwqr_task_noop_sched_out(struct preempt_notifier *notifier,
 287                                     struct task_struct *next)
 288 {
 289 }
 290
 291 static void pwqr_task_blocked_sched_in(struct preempt_notifier *notifier, int cpu)
 292 {
 293         struct pwqr_task *pwqt = container_of(notifier, struct pwqr_task, notifier);
 294         struct pwqr_sb   *sb   = pwqt->sb;
 295         unsigned long flags;
 296
 297         if (unlikely(sb->state < 0)) {
 298                 pwqr_task_detach(pwqt, sb);
 299                 pwqr_task_release(pwqt, true);
 300                 return;
 301         }
 302
 303         pwqt->notifier.ops = &pwqr_preempt_running_ops;
 304         pwqr_sb_lock_irqsave(sb, flags);
 305         __pwqr_sb_update_state(sb, 1);
 306         pwqr_sb_unlock_irqrestore(sb, flags);
 307 }
 308
 309 static void pwqr_task_sched_out(struct preempt_notifier *notifier,
 310                                struct task_struct *next)
 311 {
 312         struct pwqr_task   *pwqt = container_of(notifier, struct pwqr_task, notifier);
 313         struct pwqr_sb     *sb   = pwqt->sb;
 314         struct task_struct *p    = pwqt->task;
 315
 316         if (unlikely(p->state & TASK_DEAD) || unlikely(sb->state < 0)) {
 317                 pwqr_task_detach(pwqt, sb);
 318                 pwqr_task_release(pwqt, true);
 319                 return;
 320         }
 321         if (p->state == 0 || (p->state & (__TASK_STOPPED | __TASK_TRACED)))
 322                 return;
 323
 324         pwqt->notifier.ops = &pwqr_preempt_blocked_ops;
 325         /* see preempt.h: irq are disabled for sched_out */
 326         spin_lock(&sb->wqh.lock);
 327         __pwqr_sb_update_state(sb, -1);
 328         spin_unlock(&sb->wqh.lock);
 329 }
 330
 331 static struct preempt_ops __read_mostly pwqr_preempt_noop_ops = {
 332         .sched_in       = pwqr_task_noop_sched_in,
 333         .sched_out      = pwqr_task_noop_sched_out,
 334 };
 335
 336 static struct preempt_ops __read_mostly pwqr_preempt_running_ops = {
 337         .sched_in       = pwqr_task_noop_sched_in,
 338         .sched_out      = pwqr_task_sched_out,
 339 };
 340
 341 static struct preempt_ops __read_mostly pwqr_preempt_blocked_ops = {
 342         .sched_in       = pwqr_task_blocked_sched_in,
 343         .sched_out      = pwqr_task_sched_out,
 344 };
 345
 346 /*****************************************************************************
 347  * file descriptor
 348  */
 349 static int pwqr_open(struct inode *inode, struct file *filp)
 350 {
 351         struct pwqr_sb *sb;
 352
 353         sb = pwqr_sb_create();
 354         if (IS_ERR(sb))
 355                 return PTR_ERR(sb);
 356         filp->private_data = sb;
 357         return 0;
 358 }
 359
 360 static int pwqr_release(struct inode *inode, struct file *filp)
 361 {
 362         struct pwqr_sb *sb = filp->private_data;
 363         unsigned long flags;
 364
 365         pwqr_sb_lock_irqsave(sb, flags);
 366         sb->state = PWQR_STATE_DEAD;
 367         pwqr_sb_unlock_irqrestore(sb, flags);
 368         wake_up_all(&sb->wqh);
 369         pwqr_sb_put(sb);
 370         return 0;
 371 }
 372
 373 static long
 374 do_pwqr_wait(struct pwqr_sb *sb, struct pwqr_task *pwqt,
 375              int is_wait, struct pwqr_ioc_wait __user *arg)
 376 {
 377         unsigned long flags;
 378         struct pwqr_ioc_wait wait;
 379         long rc = 0;
 380         u32 uval;
 381
 382         preempt_notifier_unregister(&pwqt->notifier);
 383
 384         if (is_wait) {
 385                 if (copy_from_user(&wait, arg, sizeof(wait))) {
 386                         rc = -EFAULT;
 387                         goto out;
 388                 }
 389                 if (unlikely((long)wait.pwqr_uaddr % sizeof(int) != 0)) {
 390                         rc = -EINVAL;
 391                         goto out;
 392                 }
 393         }
 394
 395         pwqr_sb_lock_irqsave(sb, flags);
 396         if (sb->running + sb->waiting <= sb->concurrency) {
 397                 if (is_wait) {
 398                         while (probe_kernel_address(wait.pwqr_uaddr, uval)) {
 399                                 pwqr_sb_unlock_irqrestore(sb, flags);
 400                                 rc = get_user(uval, (u32 *)wait.pwqr_uaddr);
 401                                 if (rc)
 402                                         goto out;
 403                                 pwqr_sb_lock_irqsave(sb, flags);
 404                         }
 405
 406                         if (uval != (u32)wait.pwqr_ticket) {
 407                                 rc = -EWOULDBLOCK;
 408                                 goto out_unlock;
 409                         }
 410                 } else {
 411                         goto out_unlock;
 412                 }
 413         }
 414
 415         /* @ see <wait_event_interruptible_exclusive_locked_irq> */
 416         if (likely(sb->state >= 0)) {
 417                 DEFINE_WAIT(__wait);
 418
 419                 __wait.flags |= WQ_FLAG_EXCLUSIVE;
 420
 421                 if (is_wait) {
 422                         sb->waiting++;
 423                         __add_wait_queue(&sb->wqh, &__wait);
 424                 } else {
 425                         sb->parked++;
 426                         __add_wait_queue_tail(&sb->wqh, &__wait);
 427                 }
 428                 __pwqr_sb_update_state(sb, -1);
 429                 set_current_state(TASK_INTERRUPTIBLE);
 430
 431                 do {
 432                         if (sb->overcommit_wakes)
 433                                 break;
 434                         if (signal_pending(current)) {
 435                                 rc = -ERESTARTSYS;
 436                                 break;
 437                         }
 438                         spin_unlock_irq(&sb->wqh.lock);
 439                         schedule();
 440                         spin_lock_irq(&sb->wqh.lock);
 441                         if (is_wait)
 442                                 break;
 443                         if (sb->running + sb->waiting < sb->concurrency)
 444                                 break;
 445                 } while (likely(sb->state >= 0));
 446
 447                 __remove_wait_queue(&sb->wqh, &__wait);
 448                 __set_current_state(TASK_RUNNING);
 449
 450                 if (is_wait) {
 451                         sb->waiting--;
 452                 } else {
 453                         sb->parked--;
 454                 }
 455                 __pwqr_sb_update_state(sb, 1);
 456                 if (sb->overcommit_wakes)
 457                         sb->overcommit_wakes--;
 458                 if (sb->waiting + sb->running > sb->concurrency)
 459                         rc = -EDQUOT;
 460         }
 461
 462 out_unlock:
 463         if (unlikely(sb->state < 0))
 464                 rc = -EBADFD;
 465         pwqr_sb_unlock_irqrestore(sb, flags);
 466 out:
 467         preempt_notifier_register(&pwqt->notifier);
 468         return rc;
 469 }
 470
 471 static long do_pwqr_unregister(struct pwqr_sb *sb, struct pwqr_task *pwqt)
 472 {
 473         if (!pwqt)
 474                 return -EINVAL;
 475         if (pwqt->sb != sb)
 476                 return -ENOENT;
 477         pwqr_task_detach(pwqt, sb);
 478         pwqr_task_release(pwqt, false);
 479         return 0;
 480 }
 481
 482 static long do_pwqr_set_conc(struct pwqr_sb *sb, int conc)
 483 {
 484         long old_conc = sb->concurrency;
 485         unsigned long flags;
 486
 487         pwqr_sb_lock_irqsave(sb, flags);
 488         if (conc <= 0)
 489                 conc = num_online_cpus();
 490         if (conc != old_conc) {
 491                 sb->concurrency = conc;
 492                 __pwqr_sb_update_state(sb, 0);
 493         }
 494         pwqr_sb_unlock_irqrestore(sb, flags);
 495
 496         return old_conc;
 497 }
 498
 499 static long do_pwqr_wake(struct pwqr_sb *sb, int oc, int count)
 500 {
 501         unsigned long flags;
 502         int nwake;
 503
 504         if (count < 0)
 505                 return -EINVAL;
 506
 507         pwqr_sb_lock_irqsave(sb, flags);
 508
 509         if (oc) {
 510                 nwake = sb->waiting + sb->parked - sb->overcommit_wakes;
 511                 if (count > nwake) {
 512                         count = nwake;
 513                 } else {
 514                         nwake = count;
 515                 }
 516                 sb->overcommit_wakes += count;
 517         } else if (sb->running + sb->overcommit_wakes < sb->concurrency) {
 518                 nwake = sb->concurrency - sb->overcommit_wakes - sb->running;
 519                 if (nwake > sb->waiting + sb->parked - sb->overcommit_wakes) {
 520                         nwake = sb->waiting + sb->parked -
 521                                 sb->overcommit_wakes;
 522                 }
 523                 if (count > nwake) {
 524                         count = nwake;
 525                 } else {
 526                         nwake = count;
 527                 }
 528         } else {
 529                 /*
 530                  * This codepath deserves an explanation: waking the thread
 531                  * "for real" would overcommit, though userspace KNOWS there
 532                  * is at least one waiting thread. Such threads are threads
 533                  * that are "quarantined".
 534                  *
 535                  * Quarantined threads are woken up one by one, to allow a
 536                  * slow ramp down, trying to minimize "waiting" <-> "parked"
 537                  * flip-flops, no matter how many wakes have been asked.
 538                  *
 539                  * Since releasing one quarantined thread will wake up a
 540                  * thread that will (almost) straight go to parked mode, lie
 541                  * to userland about the fact that we unblocked that thread,
 542                  * and return 0.
 543                  *
 544                  * Though if we're already waking all waiting threads for
 545                  * overcommitting jobs, well, we don't need that.
 546                  */
 547                 count = 0;
 548                 nwake = sb->waiting > sb->overcommit_wakes;
 549         }
 550         while (nwake-- > 0)
 551                 wake_up_locked(&sb->wqh);
 552         pwqr_sb_unlock_irqrestore(sb, flags);
 553
 554         return count;
 555 }
 556
 557 static long pwqr_ioctl(struct file *filp, unsigned command, unsigned long arg)
 558 {
 559         struct pwqr_sb     *sb   = filp->private_data;
 560         struct task_struct *task = current;
 561         struct pwqr_task   *pwqt;
 562         int rc = 0;
 563
 564         switch (command) {
 565         case PWQR_GET_CONC:
 566                 return sb->concurrency;
 567         case PWQR_SET_CONC:
 568                 return do_pwqr_set_conc(sb, (int)arg);
 569
 570         case PWQR_WAKE:
 571         case PWQR_WAKE_OC:
 572                 return do_pwqr_wake(sb, command == PWQR_WAKE_OC, (int)arg);
 573
 574         case PWQR_WAIT:
 575         case PWQR_PARK:
 576         case PWQR_REGISTER:
 577         case PWQR_UNREGISTER:
 578                 break;
 579         default:
 580                 return -EINVAL;
 581         }
 582
 583         pwqt = pwqr_task_find(task);
 584         if (command == PWQR_UNREGISTER)
 585                 return do_pwqr_unregister(sb, pwqt);
 586
 587         if (pwqt == NULL) {
 588                 pwqt = pwqr_task_create(task);
 589                 if (IS_ERR(pwqt))
 590                         return PTR_ERR(pwqt);
 591                 pwqr_task_attach(pwqt, sb);
 592         } else if (unlikely(pwqt->sb != sb)) {
 593                 pwqr_task_detach(pwqt, pwqt->sb);
 594                 pwqr_task_attach(pwqt, sb);
 595         }
 596
 597         switch (command) {
 598         case PWQR_WAIT:
 599                 rc = do_pwqr_wait(sb, pwqt, true, (struct pwqr_ioc_wait __user *)arg);
 600                 break;
 601         case PWQR_PARK:
 602                 rc = do_pwqr_wait(sb, pwqt, false, NULL);
 603                 break;
 604         }
 605
 606         if (unlikely(sb->state < 0)) {
 607                 pwqr_task_detach(pwqt, pwqt->sb);
 608                 return -EBADFD;
 609         }
 610         return rc;
 611 }
 612
 613 static const struct file_operations pwqr_dev_fops = {
 614         .owner          = THIS_MODULE,
 615         .open           = pwqr_open,
 616         .release        = pwqr_release,
 617         .unlocked_ioctl = pwqr_ioctl,
 618 #ifdef CONFIG_COMPAT
 619         .compat_ioctl   = pwqr_ioctl,
 620 #endif
 621 };
 622
 623 /*****************************************************************************
 624  * module
 625  */
 626 static int __init pwqr_start(void)
 627 {
 628         int i;
 629
 630         for (i = 0; i < PWQR_HASH_SIZE; i++) {
 631                 spin_lock_init(&pwqr_tasks_hash[i].lock);
 632                 INIT_HLIST_HEAD(&pwqr_tasks_hash[i].tasks);
 633         }
 634
 635         /* Register as a character device */
 636         pwqr_major = register_chrdev(0, "pwqr", &pwqr_dev_fops);
 637         if (pwqr_major < 0) {
 638                 printk(KERN_ERR "pwqr: register_chrdev() failed\n");
 639                 return pwqr_major;
 640         }
 641
 642         /* Create a device node */
 643         pwqr_class = class_create(THIS_MODULE, PWQR_DEVICE_NAME);
 644         if (IS_ERR(pwqr_class)) {
 645                 printk(KERN_ERR "pwqr: Error creating raw class\n");
 646                 unregister_chrdev(pwqr_major, PWQR_DEVICE_NAME);
 647                 return PTR_ERR(pwqr_class);
 648         }
 649         device_create(pwqr_class, NULL, MKDEV(pwqr_major, 0), NULL, PWQR_DEVICE_NAME);
 650         printk(KERN_INFO "pwqr: PThreads Work Queues Regulator v1 loaded");
 651         return 0;
 652 }
 653
 654 static void __exit pwqr_end(void)
 655 {
 656         rcu_barrier();
 657         device_destroy(pwqr_class, MKDEV(pwqr_major, 0));
 658         class_destroy(pwqr_class);
 659         unregister_chrdev(pwqr_major, PWQR_DEVICE_NAME);
 660 }
 661
 662 module_init(pwqr_start);
 663 module_exit(pwqr_end);
 664
 665 MODULE_LICENSE("GPL");
 666 MODULE_AUTHOR("Pierre Habouzit <pierre.habouzit@intersec.com>");
 667 MODULE_DESCRIPTION("PThreads Work Queues Regulator");
 668
 669 // vim:noet:sw=8:cinoptions+=\:0,L-1,=1s: