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   1 /**************************************************************************
   2  *
   3  * Copyright (c) 2007-2009 VMware, Inc., Palo Alto, CA., USA
   4  * All Rights Reserved.
   5  *
   6  * Permission is hereby granted, free of charge, to any person obtaining a
   7  * copy of this software and associated documentation files (the
   8  * "Software"), to deal in the Software without restriction, including
   9  * without limitation the rights to use, copy, modify, merge, publish,
  10  * distribute, sub license, and/or sell copies of the Software, and to
  11  * permit persons to whom the Software is furnished to do so, subject to
  12  * the following conditions:
  13  *
  14  * The above copyright notice and this permission notice (including the
  15  * next paragraph) shall be included in all copies or substantial portions
  16  * of the Software.
  17  *
  18  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
  19  * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
  20  * FITNESS FOR A PARTICULAR PURPOSE AND NON-INFRINGEMENT. IN NO EVENT SHALL
  21  * THE COPYRIGHT HOLDERS, AUTHORS AND/OR ITS SUPPLIERS BE LIABLE FOR ANY CLAIM,
  22  * DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR
  23  * OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE
  24  * USE OR OTHER DEALINGS IN THE SOFTWARE.
  25  *
  26  **************************************************************************/
  27 /*
  28  * Authors: Thomas Hellstrom <thellstrom-at-vmware-dot-com>
  29  */
  30
  31 #include "ttm/ttm_lock.h"
  32 #include "ttm/ttm_module.h"
  33 #include <asm/atomic.h>
  34 #include <linux/errno.h>
  35 #include <linux/wait.h>
  36 #include <linux/sched.h>
  37 #include <linux/module.h>
  38
  39 #define TTM_WRITE_LOCK_PENDING    (1 << 0)
  40 #define TTM_VT_LOCK_PENDING       (1 << 1)
  41 #define TTM_SUSPEND_LOCK_PENDING  (1 << 2)
  42 #define TTM_VT_LOCK               (1 << 3)
  43 #define TTM_SUSPEND_LOCK          (1 << 4)
  44
  45 void ttm_lock_init(struct ttm_lock *lock)
  46 {
  47         spin_lock_init(&lock->lock);
  48         init_waitqueue_head(&lock->queue);
  49         lock->rw = 0;
  50         lock->flags = 0;
  51         lock->kill_takers = false;
  52         lock->signal = SIGKILL;
  53 }
  54 EXPORT_SYMBOL(ttm_lock_init);
  55
  56 void ttm_read_unlock(struct ttm_lock *lock)
  57 {
  58         spin_lock(&lock->lock);
  59         if (--lock->rw == 0)
  60                 wake_up_all(&lock->queue);
  61         spin_unlock(&lock->lock);
  62 }
  63 EXPORT_SYMBOL(ttm_read_unlock);
  64
  65 static bool __ttm_read_lock(struct ttm_lock *lock)
  66 {
  67         bool locked = false;
  68
  69         spin_lock(&lock->lock);
  70         if (unlikely(lock->kill_takers)) {
  71                 send_sig(lock->signal, current, 0);
  72                 spin_unlock(&lock->lock);
  73                 return false;
  74         }
  75         if (lock->rw >= 0 && lock->flags == 0) {
  76                 ++lock->rw;
  77                 locked = true;
  78         }
  79         spin_unlock(&lock->lock);
  80         return locked;
  81 }
  82
  83 int ttm_read_lock(struct ttm_lock *lock, bool interruptible)
  84 {
  85         int ret = 0;
  86
  87         if (interruptible)
  88                 ret = wait_event_interruptible(lock->queue,
  89                                                __ttm_read_lock(lock));
  90         else
  91                 wait_event(lock->queue, __ttm_read_lock(lock));
  92         return ret;
  93 }
  94 EXPORT_SYMBOL(ttm_read_lock);
  95
  96 static bool __ttm_read_trylock(struct ttm_lock *lock, bool *locked)
  97 {
  98         bool block = true;
  99
 100         *locked = false;
 101
 102         spin_lock(&lock->lock);
 103         if (unlikely(lock->kill_takers)) {
 104                 send_sig(lock->signal, current, 0);
 105                 spin_unlock(&lock->lock);
 106                 return false;
 107         }
 108         if (lock->rw >= 0 && lock->flags == 0) {
 109                 ++lock->rw;
 110                 block = false;
 111                 *locked = true;
 112         } else if (lock->flags == 0) {
 113                 block = false;
 114         }
 115         spin_unlock(&lock->lock);
 116
 117         return !block;
 118 }
 119
 120 int ttm_read_trylock(struct ttm_lock *lock, bool interruptible)
 121 {
 122         int ret = 0;
 123         bool locked;
 124
 125         if (interruptible)
 126                 ret = wait_event_interruptible
 127                         (lock->queue, __ttm_read_trylock(lock, &locked));
 128         else
 129                 wait_event(lock->queue, __ttm_read_trylock(lock, &locked));
 130
 131         if (unlikely(ret != 0)) {
 132                 BUG_ON(locked);
 133                 return ret;
 134         }
 135
 136         return (locked) ? 0 : -EBUSY;
 137 }
 138
 139 void ttm_write_unlock(struct ttm_lock *lock)
 140 {
 141         spin_lock(&lock->lock);
 142         lock->rw = 0;
 143         wake_up_all(&lock->queue);
 144         spin_unlock(&lock->lock);
 145 }
 146 EXPORT_SYMBOL(ttm_write_unlock);
 147
 148 static bool __ttm_write_lock(struct ttm_lock *lock)
 149 {
 150         bool locked = false;
 151
 152         spin_lock(&lock->lock);
 153         if (unlikely(lock->kill_takers)) {
 154                 send_sig(lock->signal, current, 0);
 155                 spin_unlock(&lock->lock);
 156                 return false;
 157         }
 158         if (lock->rw == 0 && ((lock->flags & ~TTM_WRITE_LOCK_PENDING) == 0)) {
 159                 lock->rw = -1;
 160                 lock->flags &= ~TTM_WRITE_LOCK_PENDING;
 161                 locked = true;
 162         } else {
 163                 lock->flags |= TTM_WRITE_LOCK_PENDING;
 164         }
 165         spin_unlock(&lock->lock);
 166         return locked;
 167 }
 168
 169 int ttm_write_lock(struct ttm_lock *lock, bool interruptible)
 170 {
 171         int ret = 0;
 172
 173         if (interruptible) {
 174                 ret = wait_event_interruptible(lock->queue,
 175                                                __ttm_write_lock(lock));
 176                 if (unlikely(ret != 0)) {
 177                         spin_lock(&lock->lock);
 178                         lock->flags &= ~TTM_WRITE_LOCK_PENDING;
 179                         wake_up_all(&lock->queue);
 180                         spin_unlock(&lock->lock);
 181                 }
 182         } else
 183                 wait_event(lock->queue, __ttm_read_lock(lock));
 184
 185         return ret;
 186 }
 187 EXPORT_SYMBOL(ttm_write_lock);
 188
 189 void ttm_write_lock_downgrade(struct ttm_lock *lock)
 190 {
 191         spin_lock(&lock->lock);
 192         lock->rw = 1;
 193         wake_up_all(&lock->queue);
 194         spin_unlock(&lock->lock);
 195 }
 196
 197 static int __ttm_vt_unlock(struct ttm_lock *lock)
 198 {
 199         int ret = 0;
 200
 201         spin_lock(&lock->lock);
 202         if (unlikely(!(lock->flags & TTM_VT_LOCK)))
 203                 ret = -EINVAL;
 204         lock->flags &= ~TTM_VT_LOCK;
 205         wake_up_all(&lock->queue);
 206         spin_unlock(&lock->lock);
 207         printk(KERN_INFO TTM_PFX "vt unlock.\n");
 208
 209         return ret;
 210 }
 211
 212 static void ttm_vt_lock_remove(struct ttm_base_object **p_base)
 213 {
 214         struct ttm_base_object *base = *p_base;
 215         struct ttm_lock *lock = container_of(base, struct ttm_lock, base);
 216         int ret;
 217
 218         *p_base = NULL;
 219         ret = __ttm_vt_unlock(lock);
 220         BUG_ON(ret != 0);
 221 }
 222
 223 static bool __ttm_vt_lock(struct ttm_lock *lock)
 224 {
 225         bool locked = false;
 226
 227         spin_lock(&lock->lock);
 228         if (lock->rw == 0) {
 229                 lock->flags &= ~TTM_VT_LOCK_PENDING;
 230                 lock->flags |= TTM_VT_LOCK;
 231                 locked = true;
 232         } else {
 233                 lock->flags |= TTM_VT_LOCK_PENDING;
 234         }
 235         spin_unlock(&lock->lock);
 236         return locked;
 237 }
 238
 239 int ttm_vt_lock(struct ttm_lock *lock,
 240                 bool interruptible,
 241                 struct ttm_object_file *tfile)
 242 {
 243         int ret = 0;
 244
 245         if (interruptible) {
 246                 ret = wait_event_interruptible(lock->queue,
 247                                                __ttm_vt_lock(lock));
 248                 if (unlikely(ret != 0)) {
 249                         spin_lock(&lock->lock);
 250                         lock->flags &= ~TTM_VT_LOCK_PENDING;
 251                         wake_up_all(&lock->queue);
 252                         spin_unlock(&lock->lock);
 253                         return ret;
 254                 }
 255         } else
 256                 wait_event(lock->queue, __ttm_vt_lock(lock));
 257
 258         /*
 259          * Add a base-object, the destructor of which will
 260          * make sure the lock is released if the client dies
 261          * while holding it.
 262          */
 263
 264         ret = ttm_base_object_init(tfile, &lock->base, false,
 265                                    ttm_lock_type, &ttm_vt_lock_remove, NULL);
 266         if (ret)
 267                 (void)__ttm_vt_unlock(lock);
 268         else {
 269                 lock->vt_holder = tfile;
 270                 printk(KERN_INFO TTM_PFX "vt lock.\n");
 271         }
 272
 273         return ret;
 274 }
 275 EXPORT_SYMBOL(ttm_vt_lock);
 276
 277 int ttm_vt_unlock(struct ttm_lock *lock)
 278 {
 279         return ttm_ref_object_base_unref(lock->vt_holder,
 280                                          lock->base.hash.key, TTM_REF_USAGE);
 281 }
 282 EXPORT_SYMBOL(ttm_vt_unlock);
 283
 284 void ttm_suspend_unlock(struct ttm_lock *lock)
 285 {
 286         spin_lock(&lock->lock);
 287         lock->flags &= ~TTM_SUSPEND_LOCK;
 288         wake_up_all(&lock->queue);
 289         spin_unlock(&lock->lock);
 290 }
 291 EXPORT_SYMBOL(ttm_suspend_unlock);
 292
 293 static bool __ttm_suspend_lock(struct ttm_lock *lock)
 294 {
 295         bool locked = false;
 296
 297         spin_lock(&lock->lock);
 298         if (lock->rw == 0) {
 299                 lock->flags &= ~TTM_SUSPEND_LOCK_PENDING;
 300                 lock->flags |= TTM_SUSPEND_LOCK;
 301                 locked = true;
 302         } else {
 303                 lock->flags |= TTM_SUSPEND_LOCK_PENDING;
 304         }
 305         spin_unlock(&lock->lock);
 306         return locked;
 307 }
 308
 309 void ttm_suspend_lock(struct ttm_lock *lock)
 310 {
 311         wait_event(lock->queue, __ttm_suspend_lock(lock));
 312 }
 313 EXPORT_SYMBOL(ttm_suspend_lock);