Ingo Molnar | 23f78d4a | 2006-06-27 02:54:53 -0700 | [diff] [blame] | 1 | /* |
| 2 | * RT-Mutexes: simple blocking mutual exclusion locks with PI support |
| 3 | * |
| 4 | * started by Ingo Molnar and Thomas Gleixner. |
| 5 | * |
| 6 | * Copyright (C) 2004-2006 Red Hat, Inc., Ingo Molnar <mingo@redhat.com> |
| 7 | * Copyright (C) 2005-2006 Timesys Corp., Thomas Gleixner <tglx@timesys.com> |
| 8 | * Copyright (C) 2005 Kihon Technologies Inc., Steven Rostedt |
| 9 | * Copyright (C) 2006 Esben Nielsen |
Steven Rostedt | d07fe82 | 2006-07-30 03:04:03 -0700 | [diff] [blame] | 10 | * |
| 11 | * See Documentation/rt-mutex-design.txt for details. |
Ingo Molnar | 23f78d4a | 2006-06-27 02:54:53 -0700 | [diff] [blame] | 12 | */ |
| 13 | #include <linux/spinlock.h> |
| 14 | #include <linux/module.h> |
| 15 | #include <linux/sched.h> |
| 16 | #include <linux/timer.h> |
| 17 | |
| 18 | #include "rtmutex_common.h" |
| 19 | |
| 20 | #ifdef CONFIG_DEBUG_RT_MUTEXES |
| 21 | # include "rtmutex-debug.h" |
| 22 | #else |
| 23 | # include "rtmutex.h" |
| 24 | #endif |
| 25 | |
| 26 | /* |
| 27 | * lock->owner state tracking: |
| 28 | * |
| 29 | * lock->owner holds the task_struct pointer of the owner. Bit 0 and 1 |
| 30 | * are used to keep track of the "owner is pending" and "lock has |
| 31 | * waiters" state. |
| 32 | * |
| 33 | * owner bit1 bit0 |
| 34 | * NULL 0 0 lock is free (fast acquire possible) |
| 35 | * NULL 0 1 invalid state |
| 36 | * NULL 1 0 Transitional State* |
| 37 | * NULL 1 1 invalid state |
| 38 | * taskpointer 0 0 lock is held (fast release possible) |
| 39 | * taskpointer 0 1 task is pending owner |
| 40 | * taskpointer 1 0 lock is held and has waiters |
| 41 | * taskpointer 1 1 task is pending owner and lock has more waiters |
| 42 | * |
| 43 | * Pending ownership is assigned to the top (highest priority) |
| 44 | * waiter of the lock, when the lock is released. The thread is woken |
| 45 | * up and can now take the lock. Until the lock is taken (bit 0 |
| 46 | * cleared) a competing higher priority thread can steal the lock |
| 47 | * which puts the woken up thread back on the waiters list. |
| 48 | * |
| 49 | * The fast atomic compare exchange based acquire and release is only |
| 50 | * possible when bit 0 and 1 of lock->owner are 0. |
| 51 | * |
| 52 | * (*) There's a small time where the owner can be NULL and the |
| 53 | * "lock has waiters" bit is set. This can happen when grabbing the lock. |
| 54 | * To prevent a cmpxchg of the owner releasing the lock, we need to set this |
| 55 | * bit before looking at the lock, hence the reason this is a transitional |
| 56 | * state. |
| 57 | */ |
| 58 | |
Pierre Peiffer | d0aa7a7 | 2007-05-09 02:35:02 -0700 | [diff] [blame] | 59 | void |
Ingo Molnar | 23f78d4a | 2006-06-27 02:54:53 -0700 | [diff] [blame] | 60 | rt_mutex_set_owner(struct rt_mutex *lock, struct task_struct *owner, |
| 61 | unsigned long mask) |
| 62 | { |
| 63 | unsigned long val = (unsigned long)owner | mask; |
| 64 | |
| 65 | if (rt_mutex_has_waiters(lock)) |
| 66 | val |= RT_MUTEX_HAS_WAITERS; |
| 67 | |
| 68 | lock->owner = (struct task_struct *)val; |
| 69 | } |
| 70 | |
| 71 | static inline void clear_rt_mutex_waiters(struct rt_mutex *lock) |
| 72 | { |
| 73 | lock->owner = (struct task_struct *) |
| 74 | ((unsigned long)lock->owner & ~RT_MUTEX_HAS_WAITERS); |
| 75 | } |
| 76 | |
| 77 | static void fixup_rt_mutex_waiters(struct rt_mutex *lock) |
| 78 | { |
| 79 | if (!rt_mutex_has_waiters(lock)) |
| 80 | clear_rt_mutex_waiters(lock); |
| 81 | } |
| 82 | |
| 83 | /* |
Ingo Molnar | 23f78d4a | 2006-06-27 02:54:53 -0700 | [diff] [blame] | 84 | * Calculate task priority from the waiter list priority |
| 85 | * |
| 86 | * Return task->normal_prio when the waiter list is empty or when |
| 87 | * the waiter is not allowed to do priority boosting |
| 88 | */ |
| 89 | int rt_mutex_getprio(struct task_struct *task) |
| 90 | { |
| 91 | if (likely(!task_has_pi_waiters(task))) |
| 92 | return task->normal_prio; |
| 93 | |
| 94 | return min(task_top_pi_waiter(task)->pi_list_entry.prio, |
| 95 | task->normal_prio); |
| 96 | } |
| 97 | |
| 98 | /* |
| 99 | * Adjust the priority of a task, after its pi_waiters got modified. |
| 100 | * |
| 101 | * This can be both boosting and unboosting. task->pi_lock must be held. |
| 102 | */ |
Pierre Peiffer | d0aa7a7 | 2007-05-09 02:35:02 -0700 | [diff] [blame] | 103 | void __rt_mutex_adjust_prio(struct task_struct *task) |
Ingo Molnar | 23f78d4a | 2006-06-27 02:54:53 -0700 | [diff] [blame] | 104 | { |
| 105 | int prio = rt_mutex_getprio(task); |
| 106 | |
| 107 | if (task->prio != prio) |
| 108 | rt_mutex_setprio(task, prio); |
| 109 | } |
| 110 | |
| 111 | /* |
| 112 | * Adjust task priority (undo boosting). Called from the exit path of |
| 113 | * rt_mutex_slowunlock() and rt_mutex_slowlock(). |
| 114 | * |
| 115 | * (Note: We do this outside of the protection of lock->wait_lock to |
| 116 | * allow the lock to be taken while or before we readjust the priority |
| 117 | * of task. We do not use the spin_xx_mutex() variants here as we are |
| 118 | * outside of the debug path.) |
| 119 | */ |
| 120 | static void rt_mutex_adjust_prio(struct task_struct *task) |
| 121 | { |
| 122 | unsigned long flags; |
| 123 | |
| 124 | spin_lock_irqsave(&task->pi_lock, flags); |
| 125 | __rt_mutex_adjust_prio(task); |
| 126 | spin_unlock_irqrestore(&task->pi_lock, flags); |
| 127 | } |
| 128 | |
| 129 | /* |
| 130 | * Max number of times we'll walk the boosting chain: |
| 131 | */ |
| 132 | int max_lock_depth = 1024; |
| 133 | |
| 134 | /* |
| 135 | * Adjust the priority chain. Also used for deadlock detection. |
| 136 | * Decreases task's usage by one - may thus free the task. |
| 137 | * Returns 0 or -EDEADLK. |
| 138 | */ |
Pierre Peiffer | d0aa7a7 | 2007-05-09 02:35:02 -0700 | [diff] [blame] | 139 | int rt_mutex_adjust_prio_chain(struct task_struct *task, |
| 140 | int deadlock_detect, |
| 141 | struct rt_mutex *orig_lock, |
| 142 | struct rt_mutex_waiter *orig_waiter, |
| 143 | struct task_struct *top_task) |
Ingo Molnar | 23f78d4a | 2006-06-27 02:54:53 -0700 | [diff] [blame] | 144 | { |
| 145 | struct rt_mutex *lock; |
| 146 | struct rt_mutex_waiter *waiter, *top_waiter = orig_waiter; |
| 147 | int detect_deadlock, ret = 0, depth = 0; |
| 148 | unsigned long flags; |
| 149 | |
| 150 | detect_deadlock = debug_rt_mutex_detect_deadlock(orig_waiter, |
| 151 | deadlock_detect); |
| 152 | |
| 153 | /* |
| 154 | * The (de)boosting is a step by step approach with a lot of |
| 155 | * pitfalls. We want this to be preemptible and we want hold a |
| 156 | * maximum of two locks per step. So we have to check |
| 157 | * carefully whether things change under us. |
| 158 | */ |
| 159 | again: |
| 160 | if (++depth > max_lock_depth) { |
| 161 | static int prev_max; |
| 162 | |
| 163 | /* |
| 164 | * Print this only once. If the admin changes the limit, |
| 165 | * print a new message when reaching the limit again. |
| 166 | */ |
| 167 | if (prev_max != max_lock_depth) { |
| 168 | prev_max = max_lock_depth; |
| 169 | printk(KERN_WARNING "Maximum lock depth %d reached " |
| 170 | "task: %s (%d)\n", max_lock_depth, |
Thomas Gleixner | 95e02ca | 2006-06-27 02:55:02 -0700 | [diff] [blame] | 171 | top_task->comm, top_task->pid); |
Ingo Molnar | 23f78d4a | 2006-06-27 02:54:53 -0700 | [diff] [blame] | 172 | } |
| 173 | put_task_struct(task); |
| 174 | |
| 175 | return deadlock_detect ? -EDEADLK : 0; |
| 176 | } |
| 177 | retry: |
| 178 | /* |
| 179 | * Task can not go away as we did a get_task() before ! |
| 180 | */ |
| 181 | spin_lock_irqsave(&task->pi_lock, flags); |
| 182 | |
| 183 | waiter = task->pi_blocked_on; |
| 184 | /* |
| 185 | * Check whether the end of the boosting chain has been |
| 186 | * reached or the state of the chain has changed while we |
| 187 | * dropped the locks. |
| 188 | */ |
| 189 | if (!waiter || !waiter->task) |
| 190 | goto out_unlock_pi; |
| 191 | |
| 192 | if (top_waiter && (!task_has_pi_waiters(task) || |
| 193 | top_waiter != task_top_pi_waiter(task))) |
| 194 | goto out_unlock_pi; |
| 195 | |
| 196 | /* |
| 197 | * When deadlock detection is off then we check, if further |
| 198 | * priority adjustment is necessary. |
| 199 | */ |
| 200 | if (!detect_deadlock && waiter->list_entry.prio == task->prio) |
| 201 | goto out_unlock_pi; |
| 202 | |
| 203 | lock = waiter->lock; |
| 204 | if (!spin_trylock(&lock->wait_lock)) { |
| 205 | spin_unlock_irqrestore(&task->pi_lock, flags); |
| 206 | cpu_relax(); |
| 207 | goto retry; |
| 208 | } |
| 209 | |
| 210 | /* Deadlock detection */ |
Thomas Gleixner | 95e02ca | 2006-06-27 02:55:02 -0700 | [diff] [blame] | 211 | if (lock == orig_lock || rt_mutex_owner(lock) == top_task) { |
Ingo Molnar | 23f78d4a | 2006-06-27 02:54:53 -0700 | [diff] [blame] | 212 | debug_rt_mutex_deadlock(deadlock_detect, orig_waiter, lock); |
| 213 | spin_unlock(&lock->wait_lock); |
| 214 | ret = deadlock_detect ? -EDEADLK : 0; |
| 215 | goto out_unlock_pi; |
| 216 | } |
| 217 | |
| 218 | top_waiter = rt_mutex_top_waiter(lock); |
| 219 | |
| 220 | /* Requeue the waiter */ |
| 221 | plist_del(&waiter->list_entry, &lock->wait_list); |
| 222 | waiter->list_entry.prio = task->prio; |
| 223 | plist_add(&waiter->list_entry, &lock->wait_list); |
| 224 | |
| 225 | /* Release the task */ |
| 226 | spin_unlock_irqrestore(&task->pi_lock, flags); |
| 227 | put_task_struct(task); |
| 228 | |
| 229 | /* Grab the next task */ |
| 230 | task = rt_mutex_owner(lock); |
Steven Rostedt | db63063 | 2006-09-29 01:59:44 -0700 | [diff] [blame] | 231 | get_task_struct(task); |
Ingo Molnar | 23f78d4a | 2006-06-27 02:54:53 -0700 | [diff] [blame] | 232 | spin_lock_irqsave(&task->pi_lock, flags); |
| 233 | |
| 234 | if (waiter == rt_mutex_top_waiter(lock)) { |
| 235 | /* Boost the owner */ |
| 236 | plist_del(&top_waiter->pi_list_entry, &task->pi_waiters); |
| 237 | waiter->pi_list_entry.prio = waiter->list_entry.prio; |
| 238 | plist_add(&waiter->pi_list_entry, &task->pi_waiters); |
| 239 | __rt_mutex_adjust_prio(task); |
| 240 | |
| 241 | } else if (top_waiter == waiter) { |
| 242 | /* Deboost the owner */ |
| 243 | plist_del(&waiter->pi_list_entry, &task->pi_waiters); |
| 244 | waiter = rt_mutex_top_waiter(lock); |
| 245 | waiter->pi_list_entry.prio = waiter->list_entry.prio; |
| 246 | plist_add(&waiter->pi_list_entry, &task->pi_waiters); |
| 247 | __rt_mutex_adjust_prio(task); |
| 248 | } |
| 249 | |
Ingo Molnar | 23f78d4a | 2006-06-27 02:54:53 -0700 | [diff] [blame] | 250 | spin_unlock_irqrestore(&task->pi_lock, flags); |
| 251 | |
| 252 | top_waiter = rt_mutex_top_waiter(lock); |
| 253 | spin_unlock(&lock->wait_lock); |
| 254 | |
| 255 | if (!detect_deadlock && waiter != top_waiter) |
| 256 | goto out_put_task; |
| 257 | |
| 258 | goto again; |
| 259 | |
| 260 | out_unlock_pi: |
| 261 | spin_unlock_irqrestore(&task->pi_lock, flags); |
| 262 | out_put_task: |
| 263 | put_task_struct(task); |
Ingo Molnar | 36c8b58 | 2006-07-03 00:25:41 -0700 | [diff] [blame] | 264 | |
Ingo Molnar | 23f78d4a | 2006-06-27 02:54:53 -0700 | [diff] [blame] | 265 | return ret; |
| 266 | } |
| 267 | |
| 268 | /* |
| 269 | * Optimization: check if we can steal the lock from the |
| 270 | * assigned pending owner [which might not have taken the |
| 271 | * lock yet]: |
| 272 | */ |
| 273 | static inline int try_to_steal_lock(struct rt_mutex *lock) |
| 274 | { |
| 275 | struct task_struct *pendowner = rt_mutex_owner(lock); |
| 276 | struct rt_mutex_waiter *next; |
| 277 | unsigned long flags; |
| 278 | |
| 279 | if (!rt_mutex_owner_pending(lock)) |
| 280 | return 0; |
| 281 | |
| 282 | if (pendowner == current) |
| 283 | return 1; |
| 284 | |
| 285 | spin_lock_irqsave(&pendowner->pi_lock, flags); |
| 286 | if (current->prio >= pendowner->prio) { |
| 287 | spin_unlock_irqrestore(&pendowner->pi_lock, flags); |
| 288 | return 0; |
| 289 | } |
| 290 | |
| 291 | /* |
| 292 | * Check if a waiter is enqueued on the pending owners |
| 293 | * pi_waiters list. Remove it and readjust pending owners |
| 294 | * priority. |
| 295 | */ |
| 296 | if (likely(!rt_mutex_has_waiters(lock))) { |
| 297 | spin_unlock_irqrestore(&pendowner->pi_lock, flags); |
| 298 | return 1; |
| 299 | } |
| 300 | |
| 301 | /* No chain handling, pending owner is not blocked on anything: */ |
| 302 | next = rt_mutex_top_waiter(lock); |
| 303 | plist_del(&next->pi_list_entry, &pendowner->pi_waiters); |
| 304 | __rt_mutex_adjust_prio(pendowner); |
| 305 | spin_unlock_irqrestore(&pendowner->pi_lock, flags); |
| 306 | |
| 307 | /* |
| 308 | * We are going to steal the lock and a waiter was |
| 309 | * enqueued on the pending owners pi_waiters queue. So |
| 310 | * we have to enqueue this waiter into |
| 311 | * current->pi_waiters list. This covers the case, |
| 312 | * where current is boosted because it holds another |
| 313 | * lock and gets unboosted because the booster is |
| 314 | * interrupted, so we would delay a waiter with higher |
| 315 | * priority as current->normal_prio. |
| 316 | * |
| 317 | * Note: in the rare case of a SCHED_OTHER task changing |
| 318 | * its priority and thus stealing the lock, next->task |
| 319 | * might be current: |
| 320 | */ |
| 321 | if (likely(next->task != current)) { |
| 322 | spin_lock_irqsave(¤t->pi_lock, flags); |
| 323 | plist_add(&next->pi_list_entry, ¤t->pi_waiters); |
| 324 | __rt_mutex_adjust_prio(current); |
| 325 | spin_unlock_irqrestore(¤t->pi_lock, flags); |
| 326 | } |
| 327 | return 1; |
| 328 | } |
| 329 | |
| 330 | /* |
| 331 | * Try to take an rt-mutex |
| 332 | * |
| 333 | * This fails |
| 334 | * - when the lock has a real owner |
| 335 | * - when a different pending owner exists and has higher priority than current |
| 336 | * |
| 337 | * Must be called with lock->wait_lock held. |
| 338 | */ |
Ingo Molnar | 9a11b49a | 2006-07-03 00:24:33 -0700 | [diff] [blame] | 339 | static int try_to_take_rt_mutex(struct rt_mutex *lock) |
Ingo Molnar | 23f78d4a | 2006-06-27 02:54:53 -0700 | [diff] [blame] | 340 | { |
| 341 | /* |
| 342 | * We have to be careful here if the atomic speedups are |
| 343 | * enabled, such that, when |
| 344 | * - no other waiter is on the lock |
| 345 | * - the lock has been released since we did the cmpxchg |
| 346 | * the lock can be released or taken while we are doing the |
| 347 | * checks and marking the lock with RT_MUTEX_HAS_WAITERS. |
| 348 | * |
| 349 | * The atomic acquire/release aware variant of |
| 350 | * mark_rt_mutex_waiters uses a cmpxchg loop. After setting |
| 351 | * the WAITERS bit, the atomic release / acquire can not |
| 352 | * happen anymore and lock->wait_lock protects us from the |
| 353 | * non-atomic case. |
| 354 | * |
| 355 | * Note, that this might set lock->owner = |
| 356 | * RT_MUTEX_HAS_WAITERS in the case the lock is not contended |
| 357 | * any more. This is fixed up when we take the ownership. |
| 358 | * This is the transitional state explained at the top of this file. |
| 359 | */ |
| 360 | mark_rt_mutex_waiters(lock); |
| 361 | |
| 362 | if (rt_mutex_owner(lock) && !try_to_steal_lock(lock)) |
| 363 | return 0; |
| 364 | |
| 365 | /* We got the lock. */ |
Ingo Molnar | 9a11b49a | 2006-07-03 00:24:33 -0700 | [diff] [blame] | 366 | debug_rt_mutex_lock(lock); |
Ingo Molnar | 23f78d4a | 2006-06-27 02:54:53 -0700 | [diff] [blame] | 367 | |
| 368 | rt_mutex_set_owner(lock, current, 0); |
| 369 | |
| 370 | rt_mutex_deadlock_account_lock(lock, current); |
| 371 | |
| 372 | return 1; |
| 373 | } |
| 374 | |
| 375 | /* |
| 376 | * Task blocks on lock. |
| 377 | * |
| 378 | * Prepare waiter and propagate pi chain |
| 379 | * |
| 380 | * This must be called with lock->wait_lock held. |
| 381 | */ |
| 382 | static int task_blocks_on_rt_mutex(struct rt_mutex *lock, |
| 383 | struct rt_mutex_waiter *waiter, |
Ingo Molnar | 9a11b49a | 2006-07-03 00:24:33 -0700 | [diff] [blame] | 384 | int detect_deadlock) |
Ingo Molnar | 23f78d4a | 2006-06-27 02:54:53 -0700 | [diff] [blame] | 385 | { |
Ingo Molnar | 36c8b58 | 2006-07-03 00:25:41 -0700 | [diff] [blame] | 386 | struct task_struct *owner = rt_mutex_owner(lock); |
Ingo Molnar | 23f78d4a | 2006-06-27 02:54:53 -0700 | [diff] [blame] | 387 | struct rt_mutex_waiter *top_waiter = waiter; |
Ingo Molnar | 23f78d4a | 2006-06-27 02:54:53 -0700 | [diff] [blame] | 388 | unsigned long flags; |
Steven Rostedt | db63063 | 2006-09-29 01:59:44 -0700 | [diff] [blame] | 389 | int chain_walk = 0, res; |
Ingo Molnar | 23f78d4a | 2006-06-27 02:54:53 -0700 | [diff] [blame] | 390 | |
| 391 | spin_lock_irqsave(¤t->pi_lock, flags); |
| 392 | __rt_mutex_adjust_prio(current); |
| 393 | waiter->task = current; |
| 394 | waiter->lock = lock; |
| 395 | plist_node_init(&waiter->list_entry, current->prio); |
| 396 | plist_node_init(&waiter->pi_list_entry, current->prio); |
| 397 | |
| 398 | /* Get the top priority waiter on the lock */ |
| 399 | if (rt_mutex_has_waiters(lock)) |
| 400 | top_waiter = rt_mutex_top_waiter(lock); |
| 401 | plist_add(&waiter->list_entry, &lock->wait_list); |
| 402 | |
| 403 | current->pi_blocked_on = waiter; |
| 404 | |
| 405 | spin_unlock_irqrestore(¤t->pi_lock, flags); |
| 406 | |
| 407 | if (waiter == rt_mutex_top_waiter(lock)) { |
| 408 | spin_lock_irqsave(&owner->pi_lock, flags); |
| 409 | plist_del(&top_waiter->pi_list_entry, &owner->pi_waiters); |
| 410 | plist_add(&waiter->pi_list_entry, &owner->pi_waiters); |
| 411 | |
| 412 | __rt_mutex_adjust_prio(owner); |
Steven Rostedt | db63063 | 2006-09-29 01:59:44 -0700 | [diff] [blame] | 413 | if (owner->pi_blocked_on) |
| 414 | chain_walk = 1; |
Ingo Molnar | 23f78d4a | 2006-06-27 02:54:53 -0700 | [diff] [blame] | 415 | spin_unlock_irqrestore(&owner->pi_lock, flags); |
| 416 | } |
Steven Rostedt | db63063 | 2006-09-29 01:59:44 -0700 | [diff] [blame] | 417 | else if (debug_rt_mutex_detect_deadlock(waiter, detect_deadlock)) |
| 418 | chain_walk = 1; |
| 419 | |
| 420 | if (!chain_walk) |
Ingo Molnar | 23f78d4a | 2006-06-27 02:54:53 -0700 | [diff] [blame] | 421 | return 0; |
| 422 | |
Steven Rostedt | db63063 | 2006-09-29 01:59:44 -0700 | [diff] [blame] | 423 | /* |
| 424 | * The owner can't disappear while holding a lock, |
| 425 | * so the owner struct is protected by wait_lock. |
| 426 | * Gets dropped in rt_mutex_adjust_prio_chain()! |
| 427 | */ |
| 428 | get_task_struct(owner); |
| 429 | |
Ingo Molnar | 23f78d4a | 2006-06-27 02:54:53 -0700 | [diff] [blame] | 430 | spin_unlock(&lock->wait_lock); |
| 431 | |
Thomas Gleixner | 95e02ca | 2006-06-27 02:55:02 -0700 | [diff] [blame] | 432 | res = rt_mutex_adjust_prio_chain(owner, detect_deadlock, lock, waiter, |
Ingo Molnar | 9a11b49a | 2006-07-03 00:24:33 -0700 | [diff] [blame] | 433 | current); |
Ingo Molnar | 23f78d4a | 2006-06-27 02:54:53 -0700 | [diff] [blame] | 434 | |
| 435 | spin_lock(&lock->wait_lock); |
| 436 | |
| 437 | return res; |
| 438 | } |
| 439 | |
| 440 | /* |
| 441 | * Wake up the next waiter on the lock. |
| 442 | * |
| 443 | * Remove the top waiter from the current tasks waiter list and from |
| 444 | * the lock waiter list. Set it as pending owner. Then wake it up. |
| 445 | * |
| 446 | * Called with lock->wait_lock held. |
| 447 | */ |
| 448 | static void wakeup_next_waiter(struct rt_mutex *lock) |
| 449 | { |
| 450 | struct rt_mutex_waiter *waiter; |
| 451 | struct task_struct *pendowner; |
| 452 | unsigned long flags; |
| 453 | |
| 454 | spin_lock_irqsave(¤t->pi_lock, flags); |
| 455 | |
| 456 | waiter = rt_mutex_top_waiter(lock); |
| 457 | plist_del(&waiter->list_entry, &lock->wait_list); |
| 458 | |
| 459 | /* |
| 460 | * Remove it from current->pi_waiters. We do not adjust a |
| 461 | * possible priority boost right now. We execute wakeup in the |
| 462 | * boosted mode and go back to normal after releasing |
| 463 | * lock->wait_lock. |
| 464 | */ |
| 465 | plist_del(&waiter->pi_list_entry, ¤t->pi_waiters); |
| 466 | pendowner = waiter->task; |
| 467 | waiter->task = NULL; |
| 468 | |
| 469 | rt_mutex_set_owner(lock, pendowner, RT_MUTEX_OWNER_PENDING); |
| 470 | |
| 471 | spin_unlock_irqrestore(¤t->pi_lock, flags); |
| 472 | |
| 473 | /* |
| 474 | * Clear the pi_blocked_on variable and enqueue a possible |
| 475 | * waiter into the pi_waiters list of the pending owner. This |
| 476 | * prevents that in case the pending owner gets unboosted a |
| 477 | * waiter with higher priority than pending-owner->normal_prio |
| 478 | * is blocked on the unboosted (pending) owner. |
| 479 | */ |
| 480 | spin_lock_irqsave(&pendowner->pi_lock, flags); |
| 481 | |
| 482 | WARN_ON(!pendowner->pi_blocked_on); |
| 483 | WARN_ON(pendowner->pi_blocked_on != waiter); |
| 484 | WARN_ON(pendowner->pi_blocked_on->lock != lock); |
| 485 | |
| 486 | pendowner->pi_blocked_on = NULL; |
| 487 | |
| 488 | if (rt_mutex_has_waiters(lock)) { |
| 489 | struct rt_mutex_waiter *next; |
| 490 | |
| 491 | next = rt_mutex_top_waiter(lock); |
| 492 | plist_add(&next->pi_list_entry, &pendowner->pi_waiters); |
| 493 | } |
| 494 | spin_unlock_irqrestore(&pendowner->pi_lock, flags); |
| 495 | |
| 496 | wake_up_process(pendowner); |
| 497 | } |
| 498 | |
| 499 | /* |
| 500 | * Remove a waiter from a lock |
| 501 | * |
| 502 | * Must be called with lock->wait_lock held |
| 503 | */ |
Pierre Peiffer | d0aa7a7 | 2007-05-09 02:35:02 -0700 | [diff] [blame] | 504 | void remove_waiter(struct rt_mutex *lock, |
| 505 | struct rt_mutex_waiter *waiter) |
Ingo Molnar | 23f78d4a | 2006-06-27 02:54:53 -0700 | [diff] [blame] | 506 | { |
| 507 | int first = (waiter == rt_mutex_top_waiter(lock)); |
Ingo Molnar | 36c8b58 | 2006-07-03 00:25:41 -0700 | [diff] [blame] | 508 | struct task_struct *owner = rt_mutex_owner(lock); |
Ingo Molnar | 23f78d4a | 2006-06-27 02:54:53 -0700 | [diff] [blame] | 509 | unsigned long flags; |
Steven Rostedt | db63063 | 2006-09-29 01:59:44 -0700 | [diff] [blame] | 510 | int chain_walk = 0; |
Ingo Molnar | 23f78d4a | 2006-06-27 02:54:53 -0700 | [diff] [blame] | 511 | |
| 512 | spin_lock_irqsave(¤t->pi_lock, flags); |
| 513 | plist_del(&waiter->list_entry, &lock->wait_list); |
| 514 | waiter->task = NULL; |
| 515 | current->pi_blocked_on = NULL; |
| 516 | spin_unlock_irqrestore(¤t->pi_lock, flags); |
| 517 | |
| 518 | if (first && owner != current) { |
| 519 | |
| 520 | spin_lock_irqsave(&owner->pi_lock, flags); |
| 521 | |
| 522 | plist_del(&waiter->pi_list_entry, &owner->pi_waiters); |
| 523 | |
| 524 | if (rt_mutex_has_waiters(lock)) { |
| 525 | struct rt_mutex_waiter *next; |
| 526 | |
| 527 | next = rt_mutex_top_waiter(lock); |
| 528 | plist_add(&next->pi_list_entry, &owner->pi_waiters); |
| 529 | } |
| 530 | __rt_mutex_adjust_prio(owner); |
| 531 | |
Steven Rostedt | db63063 | 2006-09-29 01:59:44 -0700 | [diff] [blame] | 532 | if (owner->pi_blocked_on) |
| 533 | chain_walk = 1; |
| 534 | |
Ingo Molnar | 23f78d4a | 2006-06-27 02:54:53 -0700 | [diff] [blame] | 535 | spin_unlock_irqrestore(&owner->pi_lock, flags); |
| 536 | } |
| 537 | |
| 538 | WARN_ON(!plist_node_empty(&waiter->pi_list_entry)); |
| 539 | |
Steven Rostedt | db63063 | 2006-09-29 01:59:44 -0700 | [diff] [blame] | 540 | if (!chain_walk) |
Ingo Molnar | 23f78d4a | 2006-06-27 02:54:53 -0700 | [diff] [blame] | 541 | return; |
| 542 | |
Steven Rostedt | db63063 | 2006-09-29 01:59:44 -0700 | [diff] [blame] | 543 | /* gets dropped in rt_mutex_adjust_prio_chain()! */ |
| 544 | get_task_struct(owner); |
| 545 | |
Ingo Molnar | 23f78d4a | 2006-06-27 02:54:53 -0700 | [diff] [blame] | 546 | spin_unlock(&lock->wait_lock); |
| 547 | |
Ingo Molnar | 9a11b49a | 2006-07-03 00:24:33 -0700 | [diff] [blame] | 548 | rt_mutex_adjust_prio_chain(owner, 0, lock, NULL, current); |
Ingo Molnar | 23f78d4a | 2006-06-27 02:54:53 -0700 | [diff] [blame] | 549 | |
| 550 | spin_lock(&lock->wait_lock); |
| 551 | } |
| 552 | |
| 553 | /* |
Thomas Gleixner | 95e02ca | 2006-06-27 02:55:02 -0700 | [diff] [blame] | 554 | * Recheck the pi chain, in case we got a priority setting |
| 555 | * |
| 556 | * Called from sched_setscheduler |
| 557 | */ |
| 558 | void rt_mutex_adjust_pi(struct task_struct *task) |
| 559 | { |
| 560 | struct rt_mutex_waiter *waiter; |
| 561 | unsigned long flags; |
| 562 | |
| 563 | spin_lock_irqsave(&task->pi_lock, flags); |
| 564 | |
| 565 | waiter = task->pi_blocked_on; |
| 566 | if (!waiter || waiter->list_entry.prio == task->prio) { |
| 567 | spin_unlock_irqrestore(&task->pi_lock, flags); |
| 568 | return; |
| 569 | } |
| 570 | |
Thomas Gleixner | 95e02ca | 2006-06-27 02:55:02 -0700 | [diff] [blame] | 571 | spin_unlock_irqrestore(&task->pi_lock, flags); |
| 572 | |
Steven Rostedt | db63063 | 2006-09-29 01:59:44 -0700 | [diff] [blame] | 573 | /* gets dropped in rt_mutex_adjust_prio_chain()! */ |
| 574 | get_task_struct(task); |
Ingo Molnar | 9a11b49a | 2006-07-03 00:24:33 -0700 | [diff] [blame] | 575 | rt_mutex_adjust_prio_chain(task, 0, NULL, NULL, task); |
Thomas Gleixner | 95e02ca | 2006-06-27 02:55:02 -0700 | [diff] [blame] | 576 | } |
| 577 | |
| 578 | /* |
Ingo Molnar | 23f78d4a | 2006-06-27 02:54:53 -0700 | [diff] [blame] | 579 | * Slow path lock function: |
| 580 | */ |
| 581 | static int __sched |
| 582 | rt_mutex_slowlock(struct rt_mutex *lock, int state, |
| 583 | struct hrtimer_sleeper *timeout, |
Ingo Molnar | 9a11b49a | 2006-07-03 00:24:33 -0700 | [diff] [blame] | 584 | int detect_deadlock) |
Ingo Molnar | 23f78d4a | 2006-06-27 02:54:53 -0700 | [diff] [blame] | 585 | { |
| 586 | struct rt_mutex_waiter waiter; |
| 587 | int ret = 0; |
| 588 | |
| 589 | debug_rt_mutex_init_waiter(&waiter); |
| 590 | waiter.task = NULL; |
| 591 | |
| 592 | spin_lock(&lock->wait_lock); |
| 593 | |
| 594 | /* Try to acquire the lock again: */ |
Ingo Molnar | 9a11b49a | 2006-07-03 00:24:33 -0700 | [diff] [blame] | 595 | if (try_to_take_rt_mutex(lock)) { |
Ingo Molnar | 23f78d4a | 2006-06-27 02:54:53 -0700 | [diff] [blame] | 596 | spin_unlock(&lock->wait_lock); |
| 597 | return 0; |
| 598 | } |
| 599 | |
| 600 | set_current_state(state); |
| 601 | |
| 602 | /* Setup the timer, when timeout != NULL */ |
| 603 | if (unlikely(timeout)) |
| 604 | hrtimer_start(&timeout->timer, timeout->timer.expires, |
Thomas Gleixner | c9cb2e3 | 2007-02-16 01:27:49 -0800 | [diff] [blame] | 605 | HRTIMER_MODE_ABS); |
Ingo Molnar | 23f78d4a | 2006-06-27 02:54:53 -0700 | [diff] [blame] | 606 | |
| 607 | for (;;) { |
| 608 | /* Try to acquire the lock: */ |
Ingo Molnar | 9a11b49a | 2006-07-03 00:24:33 -0700 | [diff] [blame] | 609 | if (try_to_take_rt_mutex(lock)) |
Ingo Molnar | 23f78d4a | 2006-06-27 02:54:53 -0700 | [diff] [blame] | 610 | break; |
| 611 | |
| 612 | /* |
| 613 | * TASK_INTERRUPTIBLE checks for signals and |
| 614 | * timeout. Ignored otherwise. |
| 615 | */ |
| 616 | if (unlikely(state == TASK_INTERRUPTIBLE)) { |
| 617 | /* Signal pending? */ |
| 618 | if (signal_pending(current)) |
| 619 | ret = -EINTR; |
| 620 | if (timeout && !timeout->task) |
| 621 | ret = -ETIMEDOUT; |
| 622 | if (ret) |
| 623 | break; |
| 624 | } |
| 625 | |
| 626 | /* |
| 627 | * waiter.task is NULL the first time we come here and |
| 628 | * when we have been woken up by the previous owner |
| 629 | * but the lock got stolen by a higher prio task. |
| 630 | */ |
| 631 | if (!waiter.task) { |
| 632 | ret = task_blocks_on_rt_mutex(lock, &waiter, |
Ingo Molnar | 9a11b49a | 2006-07-03 00:24:33 -0700 | [diff] [blame] | 633 | detect_deadlock); |
Ingo Molnar | 23f78d4a | 2006-06-27 02:54:53 -0700 | [diff] [blame] | 634 | /* |
| 635 | * If we got woken up by the owner then start loop |
| 636 | * all over without going into schedule to try |
| 637 | * to get the lock now: |
| 638 | */ |
| 639 | if (unlikely(!waiter.task)) |
| 640 | continue; |
| 641 | |
| 642 | if (unlikely(ret)) |
| 643 | break; |
| 644 | } |
Thomas Gleixner | 95e02ca | 2006-06-27 02:55:02 -0700 | [diff] [blame] | 645 | |
Ingo Molnar | 23f78d4a | 2006-06-27 02:54:53 -0700 | [diff] [blame] | 646 | spin_unlock(&lock->wait_lock); |
| 647 | |
| 648 | debug_rt_mutex_print_deadlock(&waiter); |
| 649 | |
Thomas Gleixner | 61a8712 | 2006-06-27 02:54:56 -0700 | [diff] [blame] | 650 | if (waiter.task) |
| 651 | schedule_rt_mutex(lock); |
Ingo Molnar | 23f78d4a | 2006-06-27 02:54:53 -0700 | [diff] [blame] | 652 | |
| 653 | spin_lock(&lock->wait_lock); |
| 654 | set_current_state(state); |
| 655 | } |
| 656 | |
| 657 | set_current_state(TASK_RUNNING); |
| 658 | |
| 659 | if (unlikely(waiter.task)) |
Ingo Molnar | 9a11b49a | 2006-07-03 00:24:33 -0700 | [diff] [blame] | 660 | remove_waiter(lock, &waiter); |
Ingo Molnar | 23f78d4a | 2006-06-27 02:54:53 -0700 | [diff] [blame] | 661 | |
| 662 | /* |
| 663 | * try_to_take_rt_mutex() sets the waiter bit |
| 664 | * unconditionally. We might have to fix that up. |
| 665 | */ |
| 666 | fixup_rt_mutex_waiters(lock); |
| 667 | |
| 668 | spin_unlock(&lock->wait_lock); |
| 669 | |
| 670 | /* Remove pending timer: */ |
| 671 | if (unlikely(timeout)) |
| 672 | hrtimer_cancel(&timeout->timer); |
| 673 | |
| 674 | /* |
| 675 | * Readjust priority, when we did not get the lock. We might |
| 676 | * have been the pending owner and boosted. Since we did not |
| 677 | * take the lock, the PI boost has to go. |
| 678 | */ |
| 679 | if (unlikely(ret)) |
| 680 | rt_mutex_adjust_prio(current); |
| 681 | |
| 682 | debug_rt_mutex_free_waiter(&waiter); |
| 683 | |
| 684 | return ret; |
| 685 | } |
| 686 | |
| 687 | /* |
| 688 | * Slow path try-lock function: |
| 689 | */ |
| 690 | static inline int |
Ingo Molnar | 9a11b49a | 2006-07-03 00:24:33 -0700 | [diff] [blame] | 691 | rt_mutex_slowtrylock(struct rt_mutex *lock) |
Ingo Molnar | 23f78d4a | 2006-06-27 02:54:53 -0700 | [diff] [blame] | 692 | { |
| 693 | int ret = 0; |
| 694 | |
| 695 | spin_lock(&lock->wait_lock); |
| 696 | |
| 697 | if (likely(rt_mutex_owner(lock) != current)) { |
| 698 | |
Ingo Molnar | 9a11b49a | 2006-07-03 00:24:33 -0700 | [diff] [blame] | 699 | ret = try_to_take_rt_mutex(lock); |
Ingo Molnar | 23f78d4a | 2006-06-27 02:54:53 -0700 | [diff] [blame] | 700 | /* |
| 701 | * try_to_take_rt_mutex() sets the lock waiters |
| 702 | * bit unconditionally. Clean this up. |
| 703 | */ |
| 704 | fixup_rt_mutex_waiters(lock); |
| 705 | } |
| 706 | |
| 707 | spin_unlock(&lock->wait_lock); |
| 708 | |
| 709 | return ret; |
| 710 | } |
| 711 | |
| 712 | /* |
| 713 | * Slow path to release a rt-mutex: |
| 714 | */ |
| 715 | static void __sched |
| 716 | rt_mutex_slowunlock(struct rt_mutex *lock) |
| 717 | { |
| 718 | spin_lock(&lock->wait_lock); |
| 719 | |
| 720 | debug_rt_mutex_unlock(lock); |
| 721 | |
| 722 | rt_mutex_deadlock_account_unlock(current); |
| 723 | |
| 724 | if (!rt_mutex_has_waiters(lock)) { |
| 725 | lock->owner = NULL; |
| 726 | spin_unlock(&lock->wait_lock); |
| 727 | return; |
| 728 | } |
| 729 | |
| 730 | wakeup_next_waiter(lock); |
| 731 | |
| 732 | spin_unlock(&lock->wait_lock); |
| 733 | |
| 734 | /* Undo pi boosting if necessary: */ |
| 735 | rt_mutex_adjust_prio(current); |
| 736 | } |
| 737 | |
| 738 | /* |
| 739 | * debug aware fast / slowpath lock,trylock,unlock |
| 740 | * |
| 741 | * The atomic acquire/release ops are compiled away, when either the |
| 742 | * architecture does not support cmpxchg or when debugging is enabled. |
| 743 | */ |
| 744 | static inline int |
| 745 | rt_mutex_fastlock(struct rt_mutex *lock, int state, |
| 746 | int detect_deadlock, |
| 747 | int (*slowfn)(struct rt_mutex *lock, int state, |
| 748 | struct hrtimer_sleeper *timeout, |
Ingo Molnar | 9a11b49a | 2006-07-03 00:24:33 -0700 | [diff] [blame] | 749 | int detect_deadlock)) |
Ingo Molnar | 23f78d4a | 2006-06-27 02:54:53 -0700 | [diff] [blame] | 750 | { |
| 751 | if (!detect_deadlock && likely(rt_mutex_cmpxchg(lock, NULL, current))) { |
| 752 | rt_mutex_deadlock_account_lock(lock, current); |
| 753 | return 0; |
| 754 | } else |
Ingo Molnar | 9a11b49a | 2006-07-03 00:24:33 -0700 | [diff] [blame] | 755 | return slowfn(lock, state, NULL, detect_deadlock); |
Ingo Molnar | 23f78d4a | 2006-06-27 02:54:53 -0700 | [diff] [blame] | 756 | } |
| 757 | |
| 758 | static inline int |
| 759 | rt_mutex_timed_fastlock(struct rt_mutex *lock, int state, |
| 760 | struct hrtimer_sleeper *timeout, int detect_deadlock, |
| 761 | int (*slowfn)(struct rt_mutex *lock, int state, |
| 762 | struct hrtimer_sleeper *timeout, |
Ingo Molnar | 9a11b49a | 2006-07-03 00:24:33 -0700 | [diff] [blame] | 763 | int detect_deadlock)) |
Ingo Molnar | 23f78d4a | 2006-06-27 02:54:53 -0700 | [diff] [blame] | 764 | { |
| 765 | if (!detect_deadlock && likely(rt_mutex_cmpxchg(lock, NULL, current))) { |
| 766 | rt_mutex_deadlock_account_lock(lock, current); |
| 767 | return 0; |
| 768 | } else |
Ingo Molnar | 9a11b49a | 2006-07-03 00:24:33 -0700 | [diff] [blame] | 769 | return slowfn(lock, state, timeout, detect_deadlock); |
Ingo Molnar | 23f78d4a | 2006-06-27 02:54:53 -0700 | [diff] [blame] | 770 | } |
| 771 | |
| 772 | static inline int |
| 773 | rt_mutex_fasttrylock(struct rt_mutex *lock, |
Ingo Molnar | 9a11b49a | 2006-07-03 00:24:33 -0700 | [diff] [blame] | 774 | int (*slowfn)(struct rt_mutex *lock)) |
Ingo Molnar | 23f78d4a | 2006-06-27 02:54:53 -0700 | [diff] [blame] | 775 | { |
| 776 | if (likely(rt_mutex_cmpxchg(lock, NULL, current))) { |
| 777 | rt_mutex_deadlock_account_lock(lock, current); |
| 778 | return 1; |
| 779 | } |
Ingo Molnar | 9a11b49a | 2006-07-03 00:24:33 -0700 | [diff] [blame] | 780 | return slowfn(lock); |
Ingo Molnar | 23f78d4a | 2006-06-27 02:54:53 -0700 | [diff] [blame] | 781 | } |
| 782 | |
| 783 | static inline void |
| 784 | rt_mutex_fastunlock(struct rt_mutex *lock, |
| 785 | void (*slowfn)(struct rt_mutex *lock)) |
| 786 | { |
| 787 | if (likely(rt_mutex_cmpxchg(lock, current, NULL))) |
| 788 | rt_mutex_deadlock_account_unlock(current); |
| 789 | else |
| 790 | slowfn(lock); |
| 791 | } |
| 792 | |
| 793 | /** |
| 794 | * rt_mutex_lock - lock a rt_mutex |
| 795 | * |
| 796 | * @lock: the rt_mutex to be locked |
| 797 | */ |
| 798 | void __sched rt_mutex_lock(struct rt_mutex *lock) |
| 799 | { |
| 800 | might_sleep(); |
| 801 | |
| 802 | rt_mutex_fastlock(lock, TASK_UNINTERRUPTIBLE, 0, rt_mutex_slowlock); |
| 803 | } |
| 804 | EXPORT_SYMBOL_GPL(rt_mutex_lock); |
| 805 | |
| 806 | /** |
| 807 | * rt_mutex_lock_interruptible - lock a rt_mutex interruptible |
| 808 | * |
| 809 | * @lock: the rt_mutex to be locked |
| 810 | * @detect_deadlock: deadlock detection on/off |
| 811 | * |
| 812 | * Returns: |
| 813 | * 0 on success |
| 814 | * -EINTR when interrupted by a signal |
| 815 | * -EDEADLK when the lock would deadlock (when deadlock detection is on) |
| 816 | */ |
| 817 | int __sched rt_mutex_lock_interruptible(struct rt_mutex *lock, |
| 818 | int detect_deadlock) |
| 819 | { |
| 820 | might_sleep(); |
| 821 | |
| 822 | return rt_mutex_fastlock(lock, TASK_INTERRUPTIBLE, |
| 823 | detect_deadlock, rt_mutex_slowlock); |
| 824 | } |
| 825 | EXPORT_SYMBOL_GPL(rt_mutex_lock_interruptible); |
| 826 | |
| 827 | /** |
| 828 | * rt_mutex_lock_interruptible_ktime - lock a rt_mutex interruptible |
| 829 | * the timeout structure is provided |
| 830 | * by the caller |
| 831 | * |
| 832 | * @lock: the rt_mutex to be locked |
| 833 | * @timeout: timeout structure or NULL (no timeout) |
| 834 | * @detect_deadlock: deadlock detection on/off |
| 835 | * |
| 836 | * Returns: |
| 837 | * 0 on success |
| 838 | * -EINTR when interrupted by a signal |
| 839 | * -ETIMEOUT when the timeout expired |
| 840 | * -EDEADLK when the lock would deadlock (when deadlock detection is on) |
| 841 | */ |
| 842 | int |
| 843 | rt_mutex_timed_lock(struct rt_mutex *lock, struct hrtimer_sleeper *timeout, |
| 844 | int detect_deadlock) |
| 845 | { |
| 846 | might_sleep(); |
| 847 | |
| 848 | return rt_mutex_timed_fastlock(lock, TASK_INTERRUPTIBLE, timeout, |
| 849 | detect_deadlock, rt_mutex_slowlock); |
| 850 | } |
| 851 | EXPORT_SYMBOL_GPL(rt_mutex_timed_lock); |
| 852 | |
| 853 | /** |
| 854 | * rt_mutex_trylock - try to lock a rt_mutex |
| 855 | * |
| 856 | * @lock: the rt_mutex to be locked |
| 857 | * |
| 858 | * Returns 1 on success and 0 on contention |
| 859 | */ |
| 860 | int __sched rt_mutex_trylock(struct rt_mutex *lock) |
| 861 | { |
| 862 | return rt_mutex_fasttrylock(lock, rt_mutex_slowtrylock); |
| 863 | } |
| 864 | EXPORT_SYMBOL_GPL(rt_mutex_trylock); |
| 865 | |
| 866 | /** |
| 867 | * rt_mutex_unlock - unlock a rt_mutex |
| 868 | * |
| 869 | * @lock: the rt_mutex to be unlocked |
| 870 | */ |
| 871 | void __sched rt_mutex_unlock(struct rt_mutex *lock) |
| 872 | { |
| 873 | rt_mutex_fastunlock(lock, rt_mutex_slowunlock); |
| 874 | } |
| 875 | EXPORT_SYMBOL_GPL(rt_mutex_unlock); |
| 876 | |
| 877 | /*** |
| 878 | * rt_mutex_destroy - mark a mutex unusable |
| 879 | * @lock: the mutex to be destroyed |
| 880 | * |
| 881 | * This function marks the mutex uninitialized, and any subsequent |
| 882 | * use of the mutex is forbidden. The mutex must not be locked when |
| 883 | * this function is called. |
| 884 | */ |
| 885 | void rt_mutex_destroy(struct rt_mutex *lock) |
| 886 | { |
| 887 | WARN_ON(rt_mutex_is_locked(lock)); |
| 888 | #ifdef CONFIG_DEBUG_RT_MUTEXES |
| 889 | lock->magic = NULL; |
| 890 | #endif |
| 891 | } |
| 892 | |
| 893 | EXPORT_SYMBOL_GPL(rt_mutex_destroy); |
| 894 | |
| 895 | /** |
| 896 | * __rt_mutex_init - initialize the rt lock |
| 897 | * |
| 898 | * @lock: the rt lock to be initialized |
| 899 | * |
| 900 | * Initialize the rt lock to unlocked state. |
| 901 | * |
| 902 | * Initializing of a locked rt lock is not allowed |
| 903 | */ |
| 904 | void __rt_mutex_init(struct rt_mutex *lock, const char *name) |
| 905 | { |
| 906 | lock->owner = NULL; |
| 907 | spin_lock_init(&lock->wait_lock); |
| 908 | plist_head_init(&lock->wait_list, &lock->wait_lock); |
| 909 | |
| 910 | debug_rt_mutex_init(lock, name); |
| 911 | } |
| 912 | EXPORT_SYMBOL_GPL(__rt_mutex_init); |
Ingo Molnar | 0cdbee9 | 2006-06-27 02:54:57 -0700 | [diff] [blame] | 913 | |
| 914 | /** |
| 915 | * rt_mutex_init_proxy_locked - initialize and lock a rt_mutex on behalf of a |
| 916 | * proxy owner |
| 917 | * |
| 918 | * @lock: the rt_mutex to be locked |
| 919 | * @proxy_owner:the task to set as owner |
| 920 | * |
| 921 | * No locking. Caller has to do serializing itself |
| 922 | * Special API call for PI-futex support |
| 923 | */ |
| 924 | void rt_mutex_init_proxy_locked(struct rt_mutex *lock, |
| 925 | struct task_struct *proxy_owner) |
| 926 | { |
| 927 | __rt_mutex_init(lock, NULL); |
Ingo Molnar | 9a11b49a | 2006-07-03 00:24:33 -0700 | [diff] [blame] | 928 | debug_rt_mutex_proxy_lock(lock, proxy_owner); |
Ingo Molnar | 0cdbee9 | 2006-06-27 02:54:57 -0700 | [diff] [blame] | 929 | rt_mutex_set_owner(lock, proxy_owner, 0); |
| 930 | rt_mutex_deadlock_account_lock(lock, proxy_owner); |
| 931 | } |
| 932 | |
| 933 | /** |
| 934 | * rt_mutex_proxy_unlock - release a lock on behalf of owner |
| 935 | * |
| 936 | * @lock: the rt_mutex to be locked |
| 937 | * |
| 938 | * No locking. Caller has to do serializing itself |
| 939 | * Special API call for PI-futex support |
| 940 | */ |
| 941 | void rt_mutex_proxy_unlock(struct rt_mutex *lock, |
| 942 | struct task_struct *proxy_owner) |
| 943 | { |
| 944 | debug_rt_mutex_proxy_unlock(lock); |
| 945 | rt_mutex_set_owner(lock, NULL, 0); |
| 946 | rt_mutex_deadlock_account_unlock(proxy_owner); |
| 947 | } |
| 948 | |
| 949 | /** |
| 950 | * rt_mutex_next_owner - return the next owner of the lock |
| 951 | * |
| 952 | * @lock: the rt lock query |
| 953 | * |
| 954 | * Returns the next owner of the lock or NULL |
| 955 | * |
| 956 | * Caller has to serialize against other accessors to the lock |
| 957 | * itself. |
| 958 | * |
| 959 | * Special API call for PI-futex support |
| 960 | */ |
| 961 | struct task_struct *rt_mutex_next_owner(struct rt_mutex *lock) |
| 962 | { |
| 963 | if (!rt_mutex_has_waiters(lock)) |
| 964 | return NULL; |
| 965 | |
| 966 | return rt_mutex_top_waiter(lock)->task; |
| 967 | } |