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         pid_t                   tgid;
  64
  65         unsigned                concurrency;
  66         unsigned                registered;
  67
  68         unsigned                running;
  69         unsigned                waiting;
  70         unsigned                parked;
  71         unsigned                overcommit_wakes;
  72
  73         int                     state;
  74 };
  75
  76 struct pwqr_task {
  77         struct preempt_notifier notifier;
  78         struct hlist_node       link;
  79         struct rcu_head         rcu;
  80         struct task_struct     *task;
  81         struct pwqr_sb         *sb;
  82 };
  83
  84 /*
  85  * Global variables
  86  */
  87 static struct class            *pwqr_class;
  88 static int                      pwqr_major;
  89 static struct pwqr_task_bucket  pwqr_tasks_hash[PWQR_HASH_SIZE];
  90 static struct preempt_ops       pwqr_preempt_running_ops;
  91 static struct preempt_ops       pwqr_preempt_blocked_ops;
  92 static struct preempt_ops       pwqr_preempt_noop_ops;
  93
  94 /*****************************************************************************
  95  * Scoreboards
  96  */
  97
  98 #define pwqr_sb_lock_irqsave(sb, flags) \
  99         spin_lock_irqsave(&(sb)->wqh.lock, flags)
 100 #define pwqr_sb_unlock_irqrestore(sb, flags) \
 101         spin_unlock_irqrestore(&(sb)->wqh.lock, flags)
 102
 103 static inline void pwqr_arm_timer(struct pwqr_sb *sb, int how, int delay)
 104 {
 105         if (timer_pending(&sb->timer) && sb->state == how)
 106                 return;
 107         mod_timer(&sb->timer, jiffies + delay);
 108         sb->state = how;
 109 }
 110
 111 static inline void __pwqr_sb_update_state(struct pwqr_sb *sb, int running_delta)
 112 {
 113         sb->running += running_delta;
 114
 115         if (sb->running < sb->concurrency && sb->waiting == 0 && sb->parked) {
 116                 pwqr_arm_timer(sb, PWQR_STATE_UC, PWQR_UC_DELAY);
 117         } else if (sb->running > sb->concurrency) {
 118                 pwqr_arm_timer(sb, PWQR_STATE_OC, PWQR_OC_DELAY);
 119         } else {
 120                 sb->state = PWQR_STATE_NONE;
 121                 if (!timer_pending(&sb->timer))
 122                         del_timer(&sb->timer);
 123         }
 124 }
 125
 126 static void pwqr_sb_timer_cb(unsigned long arg)
 127 {
 128         struct pwqr_sb *sb = (struct pwqr_sb *)arg;
 129         unsigned long flags;
 130
 131         pwqr_sb_lock_irqsave(sb, flags);
 132         if (sb->running < sb->concurrency && sb->waiting == 0 && sb->parked) {
 133                 if (sb->overcommit_wakes == 0)
 134                         wake_up_locked(&sb->wqh);
 135         }
 136         if (sb->running > sb->concurrency) {
 137                 /* See ../Documentation/pwqr.adoc */
 138         }
 139         pwqr_sb_unlock_irqrestore(sb, flags);
 140 }
 141
 142 static struct pwqr_sb *pwqr_sb_create(void)
 143 {
 144         struct pwqr_sb *sb;
 145
 146         sb = kzalloc(sizeof(struct pwqr_sb), GFP_KERNEL);
 147         if (sb == NULL)
 148                 return ERR_PTR(-ENOMEM);
 149
 150         kref_init(&sb->kref);
 151         init_waitqueue_head(&sb->wqh);
 152         sb->tgid        = current->tgid;
 153         sb->concurrency = num_online_cpus();
 154         init_timer(&sb->timer);
 155         sb->timer.function = pwqr_sb_timer_cb;
 156         sb->timer.data     = (unsigned long)sb;
 157
 158         __module_get(THIS_MODULE);
 159         return sb;
 160 }
 161 static inline void pwqr_sb_get(struct pwqr_sb *sb)
 162 {
 163         kref_get(&sb->kref);
 164 }
 165
 166 static void pwqr_sb_finalize(struct rcu_head *rcu)
 167 {
 168         struct pwqr_sb *sb = container_of(rcu, struct pwqr_sb, rcu);
 169
 170         module_put(THIS_MODULE);
 171         kfree(sb);
 172 }
 173
 174 static void pwqr_sb_release(struct kref *kref)
 175 {
 176         struct pwqr_sb *sb = container_of(kref, struct pwqr_sb, kref);
 177
 178         del_timer_sync(&sb->timer);
 179         call_rcu(&sb->rcu, pwqr_sb_finalize);
 180 }
 181 static inline void pwqr_sb_put(struct pwqr_sb *sb)
 182 {
 183         kref_put(&sb->kref, pwqr_sb_release);
 184 }
 185
 186 /*****************************************************************************
 187  * tasks
 188  */
 189 static inline struct pwqr_task_bucket *task_hbucket(struct task_struct *task)
 190 {
 191         return &pwqr_tasks_hash[hash_ptr(task, PWQR_HASH_BITS)];
 192 }
 193
 194 static struct pwqr_task *pwqr_task_find(struct task_struct *task)
 195 {
 196         struct pwqr_task_bucket *b = task_hbucket(task);
 197         struct hlist_node *node;
 198         struct pwqr_task *pwqt = NULL;
 199
 200         spin_lock(&b->lock);
 201         hlist_for_each_entry(pwqt, node, &b->tasks, link) {
 202                 if (pwqt->task == task)
 203                         break;
 204         }
 205         spin_unlock(&b->lock);
 206         return pwqt;
 207 }
 208
 209 static struct pwqr_task *pwqr_task_create(struct task_struct *task)
 210 {
 211         struct pwqr_task_bucket *b = task_hbucket(task);
 212         struct pwqr_task *pwqt;
 213
 214         pwqt = kmalloc(sizeof(*pwqt), GFP_KERNEL);
 215         if (pwqt == NULL)
 216                 return ERR_PTR(-ENOMEM);
 217
 218         preempt_notifier_init(&pwqt->notifier, &pwqr_preempt_running_ops);
 219         preempt_notifier_register(&pwqt->notifier);
 220         pwqt->task = task;
 221
 222         spin_lock(&b->lock);
 223         hlist_add_head(&pwqt->link, &b->tasks);
 224         spin_unlock(&b->lock);
 225
 226         return pwqt;
 227 }
 228
 229 __cold
 230 static void pwqr_task_detach(struct pwqr_task *pwqt, struct pwqr_sb *sb)
 231 {
 232         unsigned long flags;
 233
 234         pwqr_sb_lock_irqsave(sb, flags);
 235         sb->registered--;
 236         if (pwqt->notifier.ops == &pwqr_preempt_running_ops) {
 237                 __pwqr_sb_update_state(sb, -1);
 238         } else {
 239                 __pwqr_sb_update_state(sb, 0);
 240         }
 241         pwqr_sb_unlock_irqrestore(sb, flags);
 242         pwqr_sb_put(sb);
 243         pwqt->sb = NULL;
 244 }
 245
 246 __cold
 247 static void pwqr_task_attach(struct pwqr_task *pwqt, struct pwqr_sb *sb)
 248 {
 249         unsigned long flags;
 250
 251         pwqr_sb_lock_irqsave(sb, flags);
 252         pwqr_sb_get(pwqt->sb = sb);
 253         sb->registered++;
 254         __pwqr_sb_update_state(sb, 1);
 255         pwqr_sb_unlock_irqrestore(sb, flags);
 256 }
 257
 258 __cold
 259 static void pwqr_task_release(struct pwqr_task *pwqt, bool from_notifier)
 260 {
 261         struct pwqr_task_bucket *b = task_hbucket(pwqt->task);
 262
 263         spin_lock(&b->lock);
 264         hlist_del(&pwqt->link);
 265         spin_unlock(&b->lock);
 266         pwqt->notifier.ops = &pwqr_preempt_noop_ops;
 267
 268         if (from_notifier) {
 269                 /* When called from sched_{out,in}, it's not allowed to
 270                  * call preempt_notifier_unregister (or worse kfree())
 271                  *
 272                  * Though it's not a good idea to kfree() still registered
 273                  * callbacks if we're not dying, it'll panic on the next
 274                  * sched_{in,out} call.
 275                  */
 276                 BUG_ON(!(pwqt->task->state & TASK_DEAD));
 277                 kfree_rcu(pwqt, rcu);
 278         } else {
 279                 preempt_notifier_unregister(&pwqt->notifier);
 280                 kfree(pwqt);
 281         }
 282 }
 283
 284 static void pwqr_task_noop_sched_in(struct preempt_notifier *notifier, int cpu)
 285 {
 286 }
 287
 288 static void pwqr_task_noop_sched_out(struct preempt_notifier *notifier,
 289                                     struct task_struct *next)
 290 {
 291 }
 292
 293 static void pwqr_task_blocked_sched_in(struct preempt_notifier *notifier, int cpu)
 294 {
 295         struct pwqr_task *pwqt = container_of(notifier, struct pwqr_task, notifier);
 296         struct pwqr_sb   *sb   = pwqt->sb;
 297         unsigned long flags;
 298
 299         if (unlikely(sb->state < 0)) {
 300                 pwqr_task_detach(pwqt, sb);
 301                 pwqr_task_release(pwqt, true);
 302                 return;
 303         }
 304
 305         pwqt->notifier.ops = &pwqr_preempt_running_ops;
 306         pwqr_sb_lock_irqsave(sb, flags);
 307         __pwqr_sb_update_state(sb, 1);
 308         pwqr_sb_unlock_irqrestore(sb, flags);
 309 }
 310
 311 static void pwqr_task_sched_out(struct preempt_notifier *notifier,
 312                                struct task_struct *next)
 313 {
 314         struct pwqr_task   *pwqt = container_of(notifier, struct pwqr_task, notifier);
 315         struct pwqr_sb     *sb   = pwqt->sb;
 316         struct task_struct *p    = pwqt->task;
 317
 318         if (unlikely(p->state & TASK_DEAD) || unlikely(sb->state < 0)) {
 319                 pwqr_task_detach(pwqt, sb);
 320                 pwqr_task_release(pwqt, true);
 321                 return;
 322         }
 323         if (p->state == 0 || (p->state & (__TASK_STOPPED | __TASK_TRACED)))
 324                 return;
 325
 326         pwqt->notifier.ops = &pwqr_preempt_blocked_ops;
 327         /* see preempt.h: irq are disabled for sched_out */
 328         spin_lock(&sb->wqh.lock);
 329         __pwqr_sb_update_state(sb, -1);
 330         spin_unlock(&sb->wqh.lock);
 331 }
 332
 333 static struct preempt_ops __read_mostly pwqr_preempt_noop_ops = {
 334         .sched_in       = pwqr_task_noop_sched_in,
 335         .sched_out      = pwqr_task_noop_sched_out,
 336 };
 337
 338 static struct preempt_ops __read_mostly pwqr_preempt_running_ops = {
 339         .sched_in       = pwqr_task_noop_sched_in,
 340         .sched_out      = pwqr_task_sched_out,
 341 };
 342
 343 static struct preempt_ops __read_mostly pwqr_preempt_blocked_ops = {
 344         .sched_in       = pwqr_task_blocked_sched_in,
 345         .sched_out      = pwqr_task_sched_out,
 346 };
 347
 348 /*****************************************************************************
 349  * file descriptor
 350  */
 351 static int pwqr_open(struct inode *inode, struct file *filp)
 352 {
 353         struct pwqr_sb *sb;
 354
 355         sb = pwqr_sb_create();
 356         if (IS_ERR(sb))
 357                 return PTR_ERR(sb);
 358         filp->private_data = sb;
 359         return 0;
 360 }
 361
 362 static int pwqr_release(struct inode *inode, struct file *filp)
 363 {
 364         struct pwqr_sb *sb = filp->private_data;
 365         unsigned long flags;
 366
 367         pwqr_sb_lock_irqsave(sb, flags);
 368         sb->state = PWQR_STATE_DEAD;
 369         pwqr_sb_unlock_irqrestore(sb, flags);
 370         wake_up_all(&sb->wqh);
 371         pwqr_sb_put(sb);
 372         return 0;
 373 }
 374
 375 static long
 376 do_pwqr_wait(struct pwqr_sb *sb, struct pwqr_task *pwqt,
 377             int is_wait, struct pwqr_ioc_wait __user *arg)
 378 {
 379         unsigned long flags;
 380         struct pwqr_ioc_wait wait;
 381         long rc = 0;
 382         u32 uval;
 383
 384         preempt_notifier_unregister(&pwqt->notifier);
 385
 386         if (is_wait) {
 387                 if (copy_from_user(&wait, arg, sizeof(wait))) {
 388                         rc = -EFAULT;
 389                         goto out;
 390                 }
 391                 if (unlikely((long)wait.pwqr_uaddr % sizeof(int) != 0)) {
 392                         rc = -EINVAL;
 393                         goto out;
 394                 }
 395         }
 396
 397         pwqr_sb_lock_irqsave(sb, flags);
 398         if (sb->running + sb->waiting <= sb->concurrency) {
 399                 if (is_wait) {
 400                         while (probe_kernel_address(wait.pwqr_uaddr, uval)) {
 401                                 pwqr_sb_unlock_irqrestore(sb, flags);
 402                                 rc = get_user(uval, (u32 *)wait.pwqr_uaddr);
 403                                 if (rc)
 404                                         goto out;
 405                                 pwqr_sb_lock_irqsave(sb, flags);
 406                         }
 407
 408                         if (uval != (u32)wait.pwqr_ticket) {
 409                                 rc = -EWOULDBLOCK;
 410                                 goto out_unlock;
 411                         }
 412                 } else {
 413                         goto out_unlock;
 414                 }
 415         }
 416
 417         /* @ see <wait_event_interruptible_exclusive_locked_irq> */
 418         if (likely(sb->state >= 0)) {
 419                 DEFINE_WAIT(__wait);
 420
 421                 __wait.flags |= WQ_FLAG_EXCLUSIVE;
 422
 423                 if (is_wait) {
 424                         sb->waiting++;
 425                         __add_wait_queue(&sb->wqh, &__wait);
 426                 } else {
 427                         sb->parked++;
 428                         __add_wait_queue_tail(&sb->wqh, &__wait);
 429                 }
 430                 __pwqr_sb_update_state(sb, -1);
 431                 set_current_state(TASK_INTERRUPTIBLE);
 432
 433                 do {
 434                         if (sb->overcommit_wakes)
 435                                 break;
 436                         if (signal_pending(current)) {
 437                                 rc = -ERESTARTSYS;
 438                                 break;
 439                         }
 440                         spin_unlock_irq(&sb->wqh.lock);
 441                         schedule();
 442                         spin_lock_irq(&sb->wqh.lock);
 443                         if (is_wait)
 444                                 break;
 445                         if (sb->running + sb->waiting < sb->concurrency)
 446                                 break;
 447                 } while (likely(sb->state >= 0));
 448
 449                 __remove_wait_queue(&sb->wqh, &__wait);
 450                 __set_current_state(TASK_RUNNING);
 451
 452                 if (is_wait) {
 453                         sb->waiting--;
 454                 } else {
 455                         sb->parked--;
 456                 }
 457                 __pwqr_sb_update_state(sb, 1);
 458                 if (sb->overcommit_wakes)
 459                         sb->overcommit_wakes--;
 460                 if (sb->waiting + sb->running > sb->concurrency)
 461                         rc = -EDQUOT;
 462         }
 463
 464 out_unlock:
 465         if (unlikely(sb->state < 0))
 466                 rc = -EBADFD;
 467         pwqr_sb_unlock_irqrestore(sb, flags);
 468 out:
 469         preempt_notifier_register(&pwqt->notifier);
 470         return rc;
 471 }
 472
 473 static long do_pwqr_unregister(struct pwqr_sb *sb, struct pwqr_task *pwqt)
 474 {
 475         if (!pwqt)
 476                 return -EINVAL;
 477         if (pwqt->sb != sb)
 478                 return -ENOENT;
 479         pwqr_task_detach(pwqt, sb);
 480         pwqr_task_release(pwqt, false);
 481         return 0;
 482 }
 483
 484 static long do_pwqr_set_conc(struct pwqr_sb *sb, int conc)
 485 {
 486         long old_conc = sb->concurrency;
 487         unsigned long flags;
 488
 489         pwqr_sb_lock_irqsave(sb, flags);
 490         if (conc <= 0)
 491                 conc = num_online_cpus();
 492         if (conc != old_conc) {
 493                 sb->concurrency = conc;
 494                 __pwqr_sb_update_state(sb, 0);
 495         }
 496         pwqr_sb_unlock_irqrestore(sb, flags);
 497
 498         return old_conc;
 499 }
 500
 501 static long do_pwqr_wake(struct pwqr_sb *sb, int oc, int count)
 502 {
 503         unsigned long flags;
 504         int nwake;
 505
 506         if (count < 0)
 507                 return -EINVAL;
 508
 509         pwqr_sb_lock_irqsave(sb, flags);
 510
 511         if (oc) {
 512                 nwake = sb->waiting + sb->parked - sb->overcommit_wakes;
 513                 if (count > nwake) {
 514                         count = nwake;
 515                 } else {
 516                         nwake = count;
 517                 }
 518                 sb->overcommit_wakes += count;
 519         } else if (sb->running + sb->overcommit_wakes < sb->concurrency) {
 520                 nwake = sb->concurrency - sb->overcommit_wakes - sb->running;
 521                 if (nwake > sb->waiting + sb->parked - sb->overcommit_wakes) {
 522                         nwake = sb->waiting + sb->parked -
 523                                 sb->overcommit_wakes;
 524                 }
 525                 if (count > nwake) {
 526                         count = nwake;
 527                 } else {
 528                         nwake = count;
 529                 }
 530         } else {
 531                 /*
 532                  * This codepath deserves an explanation: waking the thread
 533                  * "for real" would overcommit, though userspace KNOWS there
 534                  * is at least one waiting thread. Such threads are threads
 535                  * that are "quarantined".
 536                  *
 537                  * Quarantined threads are woken up one by one, to allow a
 538                  * slow ramp down, trying to minimize "waiting" <-> "parked"
 539                  * flip-flops, no matter how many wakes have been asked.
 540                  *
 541                  * Since releasing one quarantined thread will wake up a
 542                  * thread that will (almost) straight go to parked mode, lie
 543                  * to userland about the fact that we unblocked that thread,
 544                  * and return 0.
 545                  *
 546                  * Though if we're already waking all waiting threads for
 547                  * overcommitting jobs, well, we don't need that.
 548                  */
 549                 count = 0;
 550                 nwake = sb->waiting > sb->overcommit_wakes;
 551         }
 552         while (nwake-- > 0)
 553                 wake_up_locked(&sb->wqh);
 554         pwqr_sb_unlock_irqrestore(sb, flags);
 555
 556         return count;
 557 }
 558
 559 static long pwqr_ioctl(struct file *filp, unsigned command, unsigned long arg)
 560 {
 561         struct pwqr_sb     *sb   = filp->private_data;
 562         struct task_struct *task = current;
 563         struct pwqr_task   *pwqt;
 564         int rc = 0;
 565
 566         if (sb->tgid != current->tgid)
 567                 return -EBADFD;
 568
 569         switch (command) {
 570         case PWQR_GET_CONC:
 571                 return sb->concurrency;
 572         case PWQR_SET_CONC:
 573                 return do_pwqr_set_conc(sb, (int)arg);
 574
 575         case PWQR_WAKE:
 576         case PWQR_WAKE_OC:
 577                 return do_pwqr_wake(sb, command == PWQR_WAKE_OC, (int)arg);
 578
 579         case PWQR_WAIT:
 580         case PWQR_PARK:
 581         case PWQR_REGISTER:
 582         case PWQR_UNREGISTER:
 583                 break;
 584         default:
 585                 return -EINVAL;
 586         }
 587
 588         pwqt = pwqr_task_find(task);
 589         if (command == PWQR_UNREGISTER)
 590                 return do_pwqr_unregister(sb, pwqt);
 591
 592         if (pwqt == NULL) {
 593                 pwqt = pwqr_task_create(task);
 594                 if (IS_ERR(pwqt))
 595                         return PTR_ERR(pwqt);
 596                 pwqr_task_attach(pwqt, sb);
 597         } else if (unlikely(pwqt->sb != sb)) {
 598                 pwqr_task_detach(pwqt, pwqt->sb);
 599                 pwqr_task_attach(pwqt, sb);
 600         }
 601
 602         switch (command) {
 603         case PWQR_WAIT:
 604                 rc = do_pwqr_wait(sb, pwqt, true, (struct pwqr_ioc_wait __user *)arg);
 605                 break;
 606         case PWQR_PARK:
 607                 rc = do_pwqr_wait(sb, pwqt, false, NULL);
 608                 break;
 609         }
 610
 611         if (unlikely(sb->state < 0)) {
 612                 pwqr_task_detach(pwqt, pwqt->sb);
 613                 return -EBADFD;
 614         }
 615         return rc;
 616 }
 617
 618 static const struct file_operations pwqr_dev_fops = {
 619         .owner          = THIS_MODULE,
 620         .open           = pwqr_open,
 621         .release        = pwqr_release,
 622         .unlocked_ioctl = pwqr_ioctl,
 623 #ifdef CONFIG_COMPAT
 624         .compat_ioctl   = pwqr_ioctl,
 625 #endif
 626 };
 627
 628 /*****************************************************************************
 629  * module
 630  */
 631 static int __init pwqr_start(void)
 632 {
 633         int i;
 634
 635         for (i = 0; i < PWQR_HASH_SIZE; i++) {
 636                 spin_lock_init(&pwqr_tasks_hash[i].lock);
 637                 INIT_HLIST_HEAD(&pwqr_tasks_hash[i].tasks);
 638         }
 639
 640         /* Register as a character device */
 641         pwqr_major = register_chrdev(0, "pwqr", &pwqr_dev_fops);
 642         if (pwqr_major < 0) {
 643                 printk(KERN_ERR "pwqr: register_chrdev() failed\n");
 644                 return pwqr_major;
 645         }
 646
 647         /* Create a device node */
 648         pwqr_class = class_create(THIS_MODULE, PWQR_DEVICE_NAME);
 649         if (IS_ERR(pwqr_class)) {
 650                 printk(KERN_ERR "pwqr: Error creating raw class\n");
 651                 unregister_chrdev(pwqr_major, PWQR_DEVICE_NAME);
 652                 return PTR_ERR(pwqr_class);
 653         }
 654         device_create(pwqr_class, NULL, MKDEV(pwqr_major, 0), NULL, PWQR_DEVICE_NAME);
 655         printk(KERN_INFO "pwqr: PThreads Work Queues Regulator v1 loaded");
 656         return 0;
 657 }
 658
 659 static void __exit pwqr_end(void)
 660 {
 661         rcu_barrier();
 662         device_destroy(pwqr_class, MKDEV(pwqr_major, 0));
 663         class_destroy(pwqr_class);
 664         unregister_chrdev(pwqr_major, PWQR_DEVICE_NAME);
 665 }
 666
 667 module_init(pwqr_start);
 668 module_exit(pwqr_end);
 669
 670 MODULE_LICENSE("GPL");
 671 MODULE_AUTHOR("Pierre Habouzit <pierre.habouzit@intersec.com>");
 672 MODULE_DESCRIPTION("PThreads Work Queues Regulator");
 673
 674 // vim:noet:sw=8:cinoptions+=\:0,L-1,=1s: