drivers/staging/dst/thread_pool.c

   1 /*
   2  * 2007+ Copyright (c) Evgeniy Polyakov <zbr@ioremap.net>
   3  * All rights reserved.
   4  *
   5  * This program is free software; you can redistribute it and/or modify
   6  * it under the terms of the GNU General Public License as published by
   7  * the Free Software Foundation; either version 2 of the License, or
   8  * (at your option) any later version.
   9  *
  10  * This program is distributed in the hope that it will be useful,
  11  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  12  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  13  * GNU General Public License for more details.
  14  */
  15
  16 #include <linux/kernel.h>
  17 #include <linux/dst.h>
  18 #include <linux/kthread.h>
  19 #include <linux/slab.h>
  20
  21 /*
  22  * Thread pool abstraction allows to schedule a work to be performed
  23  * on behalf of kernel thread. One does not operate with threads itself,
  24  * instead user provides setup and cleanup callbacks for thread pool itself,
  25  * and action and cleanup callbacks for each submitted work.
  26  *
  27  * Each worker has private data initialized at creation time and data,
  28  * provided by user at scheduling time.
  29  *
  30  * When action is being performed, thread can not be used by other users,
  31  * instead they will sleep until there is free thread to pick their work.
  32  */
  33 struct thread_pool_worker {
  34         struct list_head        worker_entry;
  35
  36         struct task_struct      *thread;
  37
  38         struct thread_pool      *pool;
  39
  40         int                     error;
  41         int                     has_data;
  42         int                     need_exit;
  43         unsigned int            id;
  44
  45         wait_queue_head_t       wait;
  46
  47         void                    *private;
  48         void                    *schedule_data;
  49
  50         int                     (*action)(void *private, void *schedule_data);
  51         void                    (*cleanup)(void *private);
  52 };
  53
  54 static void thread_pool_exit_worker(struct thread_pool_worker *w)
  55 {
  56         kthread_stop(w->thread);
  57
  58         w->cleanup(w->private);
  59         kfree(w);
  60 }
  61
  62 /*
  63  * Called to mark thread as ready and allow users to schedule new work.
  64  */
  65 static void thread_pool_worker_make_ready(struct thread_pool_worker *w)
  66 {
  67         struct thread_pool *p = w->pool;
  68
  69         mutex_lock(&p->thread_lock);
  70
  71         if (!w->need_exit) {
  72                 list_move_tail(&w->worker_entry, &p->ready_list);
  73                 w->has_data = 0;
  74                 mutex_unlock(&p->thread_lock);
  75
  76                 wake_up(&p->wait);
  77         } else {
  78                 p->thread_num--;
  79                 list_del(&w->worker_entry);
  80                 mutex_unlock(&p->thread_lock);
  81
  82                 thread_pool_exit_worker(w);
  83         }
  84 }
  85
  86 /*
  87  * Thread action loop: waits until there is new work.
  88  */
  89 static int thread_pool_worker_func(void *data)
  90 {
  91         struct thread_pool_worker *w = data;
  92
  93         while (!kthread_should_stop()) {
  94                 wait_event_interruptible(w->wait,
  95                         kthread_should_stop() || w->has_data);
  96
  97                 if (kthread_should_stop())
  98                         break;
  99
 100                 if (!w->has_data)
 101                         continue;
 102
 103                 w->action(w->private, w->schedule_data);
 104                 thread_pool_worker_make_ready(w);
 105         }
 106
 107         return 0;
 108 }
 109
 110 /*
 111  * Remove single worker without specifying which one.
 112  */
 113 void thread_pool_del_worker(struct thread_pool *p)
 114 {
 115         struct thread_pool_worker *w = NULL;
 116
 117         while (!w && p->thread_num) {
 118                 wait_event(p->wait, !list_empty(&p->ready_list) ||
 119                                 !p->thread_num);
 120
 121                 dprintk("%s: locking list_empty: %d, thread_num: %d.\n",
 122                                 __func__, list_empty(&p->ready_list),
 123                                 p->thread_num);
 124
 125                 mutex_lock(&p->thread_lock);
 126                 if (!list_empty(&p->ready_list)) {
 127                         w = list_first_entry(&p->ready_list,
 128                                         struct thread_pool_worker,
 129                                         worker_entry);
 130
 131                         dprintk("%s: deleting w: %p, thread_num: %d, "
 132                                         "list: %p [%p.%p].\n", __func__,
 133                                         w, p->thread_num, &p->ready_list,
 134                                         p->ready_list.prev, p->ready_list.next);
 135
 136                         p->thread_num--;
 137                         list_del(&w->worker_entry);
 138                 }
 139                 mutex_unlock(&p->thread_lock);
 140         }
 141
 142         if (w)
 143                 thread_pool_exit_worker(w);
 144         dprintk("%s: deleted w: %p, thread_num: %d.\n",
 145                         __func__, w, p->thread_num);
 146 }
 147
 148 /*
 149  * Remove a worker with given ID.
 150  */
 151 void thread_pool_del_worker_id(struct thread_pool *p, unsigned int id)
 152 {
 153         struct thread_pool_worker *w;
 154         int found = 0;
 155
 156         mutex_lock(&p->thread_lock);
 157         list_for_each_entry(w, &p->ready_list, worker_entry) {
 158                 if (w->id == id) {
 159                         found = 1;
 160                         p->thread_num--;
 161                         list_del(&w->worker_entry);
 162                         break;
 163                 }
 164         }
 165
 166         if (!found) {
 167                 list_for_each_entry(w, &p->active_list, worker_entry) {
 168                         if (w->id == id) {
 169                                 w->need_exit = 1;
 170                                 break;
 171                         }
 172                 }
 173         }
 174         mutex_unlock(&p->thread_lock);
 175
 176         if (found)
 177                 thread_pool_exit_worker(w);
 178 }
 179
 180 /*
 181  * Add new worker thread with given parameters.
 182  * If initialization callback fails, return error.
 183  */
 184 int thread_pool_add_worker(struct thread_pool *p,
 185                 char *name,
 186                 unsigned int id,
 187                 void *(*init)(void *private),
 188                 void (*cleanup)(void *private),
 189                 void *private)
 190 {
 191         struct thread_pool_worker *w;
 192         int err = -ENOMEM;
 193
 194         w = kzalloc(sizeof(struct thread_pool_worker), GFP_KERNEL);
 195         if (!w)
 196                 goto err_out_exit;
 197
 198         w->pool = p;
 199         init_waitqueue_head(&w->wait);
 200         w->cleanup = cleanup;
 201         w->id = id;
 202
 203         w->thread = kthread_run(thread_pool_worker_func, w, "%s", name);
 204         if (IS_ERR(w->thread)) {
 205                 err = PTR_ERR(w->thread);
 206                 goto err_out_free;
 207         }
 208
 209         w->private = init(private);
 210         if (IS_ERR(w->private)) {
 211                 err = PTR_ERR(w->private);
 212                 goto err_out_stop_thread;
 213         }
 214
 215         mutex_lock(&p->thread_lock);
 216         list_add_tail(&w->worker_entry, &p->ready_list);
 217         p->thread_num++;
 218         mutex_unlock(&p->thread_lock);
 219
 220         return 0;
 221
 222 err_out_stop_thread:
 223         kthread_stop(w->thread);
 224 err_out_free:
 225         kfree(w);
 226 err_out_exit:
 227         return err;
 228 }
 229
 230 /*
 231  * Destroy the whole pool.
 232  */
 233 void thread_pool_destroy(struct thread_pool *p)
 234 {
 235         while (p->thread_num) {
 236                 dprintk("%s: num: %d.\n", __func__, p->thread_num);
 237                 thread_pool_del_worker(p);
 238         }
 239
 240         kfree(p);
 241 }
 242
 243 /*
 244  * Create a pool with given number of threads.
 245  * They will have sequential IDs started from zero.
 246  */
 247 struct thread_pool *thread_pool_create(int num, char *name,
 248                 void *(*init)(void *private),
 249                 void (*cleanup)(void *private),
 250                 void *private)
 251 {
 252         struct thread_pool_worker *w, *tmp;
 253         struct thread_pool *p;
 254         int err = -ENOMEM;
 255         int i;
 256
 257         p = kzalloc(sizeof(struct thread_pool), GFP_KERNEL);
 258         if (!p)
 259                 goto err_out_exit;
 260
 261         init_waitqueue_head(&p->wait);
 262         mutex_init(&p->thread_lock);
 263         INIT_LIST_HEAD(&p->ready_list);
 264         INIT_LIST_HEAD(&p->active_list);
 265         p->thread_num = 0;
 266
 267         for (i = 0; i < num; ++i) {
 268                 err = thread_pool_add_worker(p, name, i, init,
 269                                 cleanup, private);
 270                 if (err)
 271                         goto err_out_free_all;
 272         }
 273
 274         return p;
 275
 276 err_out_free_all:
 277         list_for_each_entry_safe(w, tmp, &p->ready_list, worker_entry) {
 278                 list_del(&w->worker_entry);
 279                 thread_pool_exit_worker(w);
 280         }
 281         kfree(p);
 282 err_out_exit:
 283         return ERR_PTR(err);
 284 }
 285
 286 /*
 287  * Schedule execution of the action on a given thread,
 288  * provided ID pointer has to match previously stored
 289  * private data.
 290  */
 291 int thread_pool_schedule_private(struct thread_pool *p,
 292                 int (*setup)(void *private, void *data),
 293                 int (*action)(void *private, void *data),
 294                 void *data, long timeout, void *id)
 295 {
 296         struct thread_pool_worker *w, *tmp, *worker = NULL;
 297         int err = 0;
 298
 299         while (!worker && !err) {
 300                 timeout = wait_event_interruptible_timeout(p->wait,
 301                                 !list_empty(&p->ready_list),
 302                                 timeout);
 303
 304                 if (!timeout) {
 305                         err = -ETIMEDOUT;
 306                         break;
 307                 }
 308
 309                 worker = NULL;
 310                 mutex_lock(&p->thread_lock);
 311                 list_for_each_entry_safe(w, tmp, &p->ready_list, worker_entry) {
 312                         if (id && id != w->private)
 313                                 continue;
 314
 315                         worker = w;
 316
 317                         list_move_tail(&w->worker_entry, &p->active_list);
 318
 319                         err = setup(w->private, data);
 320                         if (!err) {
 321                                 w->schedule_data = data;
 322                                 w->action = action;
 323                                 w->has_data = 1;
 324                                 wake_up(&w->wait);
 325                         } else {
 326                                 list_move_tail(&w->worker_entry,
 327                                                 &p->ready_list);
 328                         }
 329
 330                         break;
 331                 }
 332                 mutex_unlock(&p->thread_lock);
 333         }
 334
 335         return err;
 336 }
 337
 338 /*
 339  * Schedule execution on arbitrary thread from the pool.
 340  */
 341 int thread_pool_schedule(struct thread_pool *p,
 342                 int (*setup)(void *private, void *data),
 343                 int (*action)(void *private, void *data),
 344                 void *data, long timeout)
 345 {
 346         return thread_pool_schedule_private(p, setup,
 347                         action, data, timeout, NULL);
 348 }