| 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 |
| 10 | * |
| 11 | * See Documentation/locking/rt-mutex-design.txt for details. |
| 12 | */ |
| 13 | #include <linux/spinlock.h> |
| 14 | #include <linux/export.h> |
| 15 | #include <linux/sched.h> |
| 16 | #include <linux/sched/rt.h> |
| 17 | #include <linux/sched/deadline.h> |
| 18 | #include <linux/timer.h> |
| 19 | |
| 20 | #include "rtmutex_common.h" |
| 21 | |
| 22 | /* |
| 23 | * lock->owner state tracking: |
| 24 | * |
| 25 | * lock->owner holds the task_struct pointer of the owner. Bit 0 |
| 26 | * is used to keep track of the "lock has waiters" state. |
| 27 | * |
| 28 | * owner bit0 |
| 29 | * NULL 0 lock is free (fast acquire possible) |
| 30 | * NULL 1 lock is free and has waiters and the top waiter |
| 31 | * is going to take the lock* |
| 32 | * taskpointer 0 lock is held (fast release possible) |
| 33 | * taskpointer 1 lock is held and has waiters** |
| 34 | * |
| 35 | * The fast atomic compare exchange based acquire and release is only |
| 36 | * possible when bit 0 of lock->owner is 0. |
| 37 | * |
| 38 | * (*) It also can be a transitional state when grabbing the lock |
| 39 | * with ->wait_lock is held. To prevent any fast path cmpxchg to the lock, |
| 40 | * we need to set the bit0 before looking at the lock, and the owner may be |
| 41 | * NULL in this small time, hence this can be a transitional state. |
| 42 | * |
| 43 | * (**) There is a small time when bit 0 is set but there are no |
| 44 | * waiters. This can happen when grabbing the lock in the slow path. |
| 45 | * To prevent a cmpxchg of the owner releasing the lock, we need to |
| 46 | * set this bit before looking at the lock. |
| 47 | */ |
| 48 | |
| 49 | static void |
| 50 | rt_mutex_set_owner(struct rt_mutex *lock, struct task_struct *owner) |
| 51 | { |
| 52 | unsigned long val = (unsigned long)owner; |
| 53 | |
| 54 | if (rt_mutex_has_waiters(lock)) |
| 55 | val |= RT_MUTEX_HAS_WAITERS; |
| 56 | |
| 57 | lock->owner = (struct task_struct *)val; |
| 58 | } |
| 59 | |
| 60 | static inline void clear_rt_mutex_waiters(struct rt_mutex *lock) |
| 61 | { |
| 62 | lock->owner = (struct task_struct *) |
| 63 | ((unsigned long)lock->owner & ~RT_MUTEX_HAS_WAITERS); |
| 64 | } |
| 65 | |
| 66 | static void fixup_rt_mutex_waiters(struct rt_mutex *lock) |
| 67 | { |
| 68 | if (!rt_mutex_has_waiters(lock)) |
| 69 | clear_rt_mutex_waiters(lock); |
| 70 | } |
| 71 | |
| 72 | /* |
| 73 | * We can speed up the acquire/release, if the architecture |
| 74 | * supports cmpxchg and if there's no debugging state to be set up |
| 75 | */ |
| 76 | #if defined(__HAVE_ARCH_CMPXCHG) && !defined(CONFIG_DEBUG_RT_MUTEXES) |
| 77 | # define rt_mutex_cmpxchg(l,c,n) (cmpxchg(&l->owner, c, n) == c) |
| 78 | static inline void mark_rt_mutex_waiters(struct rt_mutex *lock) |
| 79 | { |
| 80 | unsigned long owner, *p = (unsigned long *) &lock->owner; |
| 81 | |
| 82 | do { |
| 83 | owner = *p; |
| 84 | } while (cmpxchg(p, owner, owner | RT_MUTEX_HAS_WAITERS) != owner); |
| 85 | } |
| 86 | |
| 87 | /* |
| 88 | * Safe fastpath aware unlock: |
| 89 | * 1) Clear the waiters bit |
| 90 | * 2) Drop lock->wait_lock |
| 91 | * 3) Try to unlock the lock with cmpxchg |
| 92 | */ |
| 93 | static inline bool unlock_rt_mutex_safe(struct rt_mutex *lock) |
| 94 | __releases(lock->wait_lock) |
| 95 | { |
| 96 | struct task_struct *owner = rt_mutex_owner(lock); |
| 97 | |
| 98 | clear_rt_mutex_waiters(lock); |
| 99 | raw_spin_unlock(&lock->wait_lock); |
| 100 | /* |
| 101 | * If a new waiter comes in between the unlock and the cmpxchg |
| 102 | * we have two situations: |
| 103 | * |
| 104 | * unlock(wait_lock); |
| 105 | * lock(wait_lock); |
| 106 | * cmpxchg(p, owner, 0) == owner |
| 107 | * mark_rt_mutex_waiters(lock); |
| 108 | * acquire(lock); |
| 109 | * or: |
| 110 | * |
| 111 | * unlock(wait_lock); |
| 112 | * lock(wait_lock); |
| 113 | * mark_rt_mutex_waiters(lock); |
| 114 | * |
| 115 | * cmpxchg(p, owner, 0) != owner |
| 116 | * enqueue_waiter(); |
| 117 | * unlock(wait_lock); |
| 118 | * lock(wait_lock); |
| 119 | * wake waiter(); |
| 120 | * unlock(wait_lock); |
| 121 | * lock(wait_lock); |
| 122 | * acquire(lock); |
| 123 | */ |
| 124 | return rt_mutex_cmpxchg(lock, owner, NULL); |
| 125 | } |
| 126 | |
| 127 | #else |
| 128 | # define rt_mutex_cmpxchg(l,c,n) (0) |
| 129 | static inline void mark_rt_mutex_waiters(struct rt_mutex *lock) |
| 130 | { |
| 131 | lock->owner = (struct task_struct *) |
| 132 | ((unsigned long)lock->owner | RT_MUTEX_HAS_WAITERS); |
| 133 | } |
| 134 | |
| 135 | /* |
| 136 | * Simple slow path only version: lock->owner is protected by lock->wait_lock. |
| 137 | */ |
| 138 | static inline bool unlock_rt_mutex_safe(struct rt_mutex *lock) |
| 139 | __releases(lock->wait_lock) |
| 140 | { |
| 141 | lock->owner = NULL; |
| 142 | raw_spin_unlock(&lock->wait_lock); |
| 143 | return true; |
| 144 | } |
| 145 | #endif |
| 146 | |
| 147 | static inline int |
| 148 | rt_mutex_waiter_less(struct rt_mutex_waiter *left, |
| 149 | struct rt_mutex_waiter *right) |
| 150 | { |
| 151 | if (left->prio < right->prio) |
| 152 | return 1; |
| 153 | |
| 154 | /* |
| 155 | * If both waiters have dl_prio(), we check the deadlines of the |
| 156 | * associated tasks. |
| 157 | * If left waiter has a dl_prio(), and we didn't return 1 above, |
| 158 | * then right waiter has a dl_prio() too. |
| 159 | */ |
| 160 | if (dl_prio(left->prio)) |
| 161 | return (left->task->dl.deadline < right->task->dl.deadline); |
| 162 | |
| 163 | return 0; |
| 164 | } |
| 165 | |
| 166 | static void |
| 167 | rt_mutex_enqueue(struct rt_mutex *lock, struct rt_mutex_waiter *waiter) |
| 168 | { |
| 169 | struct rb_node **link = &lock->waiters.rb_node; |
| 170 | struct rb_node *parent = NULL; |
| 171 | struct rt_mutex_waiter *entry; |
| 172 | int leftmost = 1; |
| 173 | |
| 174 | while (*link) { |
| 175 | parent = *link; |
| 176 | entry = rb_entry(parent, struct rt_mutex_waiter, tree_entry); |
| 177 | if (rt_mutex_waiter_less(waiter, entry)) { |
| 178 | link = &parent->rb_left; |
| 179 | } else { |
| 180 | link = &parent->rb_right; |
| 181 | leftmost = 0; |
| 182 | } |
| 183 | } |
| 184 | |
| 185 | if (leftmost) |
| 186 | lock->waiters_leftmost = &waiter->tree_entry; |
| 187 | |
| 188 | rb_link_node(&waiter->tree_entry, parent, link); |
| 189 | rb_insert_color(&waiter->tree_entry, &lock->waiters); |
| 190 | } |
| 191 | |
| 192 | static void |
| 193 | rt_mutex_dequeue(struct rt_mutex *lock, struct rt_mutex_waiter *waiter) |
| 194 | { |
| 195 | if (RB_EMPTY_NODE(&waiter->tree_entry)) |
| 196 | return; |
| 197 | |
| 198 | if (lock->waiters_leftmost == &waiter->tree_entry) |
| 199 | lock->waiters_leftmost = rb_next(&waiter->tree_entry); |
| 200 | |
| 201 | rb_erase(&waiter->tree_entry, &lock->waiters); |
| 202 | RB_CLEAR_NODE(&waiter->tree_entry); |
| 203 | } |
| 204 | |
| 205 | static void |
| 206 | rt_mutex_enqueue_pi(struct task_struct *task, struct rt_mutex_waiter *waiter) |
| 207 | { |
| 208 | struct rb_node **link = &task->pi_waiters.rb_node; |
| 209 | struct rb_node *parent = NULL; |
| 210 | struct rt_mutex_waiter *entry; |
| 211 | int leftmost = 1; |
| 212 | |
| 213 | while (*link) { |
| 214 | parent = *link; |
| 215 | entry = rb_entry(parent, struct rt_mutex_waiter, pi_tree_entry); |
| 216 | if (rt_mutex_waiter_less(waiter, entry)) { |
| 217 | link = &parent->rb_left; |
| 218 | } else { |
| 219 | link = &parent->rb_right; |
| 220 | leftmost = 0; |
| 221 | } |
| 222 | } |
| 223 | |
| 224 | if (leftmost) |
| 225 | task->pi_waiters_leftmost = &waiter->pi_tree_entry; |
| 226 | |
| 227 | rb_link_node(&waiter->pi_tree_entry, parent, link); |
| 228 | rb_insert_color(&waiter->pi_tree_entry, &task->pi_waiters); |
| 229 | } |
| 230 | |
| 231 | static void |
| 232 | rt_mutex_dequeue_pi(struct task_struct *task, struct rt_mutex_waiter *waiter) |
| 233 | { |
| 234 | if (RB_EMPTY_NODE(&waiter->pi_tree_entry)) |
| 235 | return; |
| 236 | |
| 237 | if (task->pi_waiters_leftmost == &waiter->pi_tree_entry) |
| 238 | task->pi_waiters_leftmost = rb_next(&waiter->pi_tree_entry); |
| 239 | |
| 240 | rb_erase(&waiter->pi_tree_entry, &task->pi_waiters); |
| 241 | RB_CLEAR_NODE(&waiter->pi_tree_entry); |
| 242 | } |
| 243 | |
| 244 | /* |
| 245 | * Calculate task priority from the waiter tree priority |
| 246 | * |
| 247 | * Return task->normal_prio when the waiter tree is empty or when |
| 248 | * the waiter is not allowed to do priority boosting |
| 249 | */ |
| 250 | int rt_mutex_getprio(struct task_struct *task) |
| 251 | { |
| 252 | if (likely(!task_has_pi_waiters(task))) |
| 253 | return task->normal_prio; |
| 254 | |
| 255 | return min(task_top_pi_waiter(task)->prio, |
| 256 | task->normal_prio); |
| 257 | } |
| 258 | |
| 259 | struct task_struct *rt_mutex_get_top_task(struct task_struct *task) |
| 260 | { |
| 261 | if (likely(!task_has_pi_waiters(task))) |
| 262 | return NULL; |
| 263 | |
| 264 | return task_top_pi_waiter(task)->task; |
| 265 | } |
| 266 | |
| 267 | /* |
| 268 | * Called by sched_setscheduler() to check whether the priority change |
| 269 | * is overruled by a possible priority boosting. |
| 270 | */ |
| 271 | int rt_mutex_check_prio(struct task_struct *task, int newprio) |
| 272 | { |
| 273 | if (!task_has_pi_waiters(task)) |
| 274 | return 0; |
| 275 | |
| 276 | return task_top_pi_waiter(task)->task->prio <= newprio; |
| 277 | } |
| 278 | |
| 279 | /* |
| 280 | * Adjust the priority of a task, after its pi_waiters got modified. |
| 281 | * |
| 282 | * This can be both boosting and unboosting. task->pi_lock must be held. |
| 283 | */ |
| 284 | static void __rt_mutex_adjust_prio(struct task_struct *task) |
| 285 | { |
| 286 | int prio = rt_mutex_getprio(task); |
| 287 | |
| 288 | if (task->prio != prio || dl_prio(prio)) |
| 289 | rt_mutex_setprio(task, prio); |
| 290 | } |
| 291 | |
| 292 | /* |
| 293 | * Adjust task priority (undo boosting). Called from the exit path of |
| 294 | * rt_mutex_slowunlock() and rt_mutex_slowlock(). |
| 295 | * |
| 296 | * (Note: We do this outside of the protection of lock->wait_lock to |
| 297 | * allow the lock to be taken while or before we readjust the priority |
| 298 | * of task. We do not use the spin_xx_mutex() variants here as we are |
| 299 | * outside of the debug path.) |
| 300 | */ |
| 301 | static void rt_mutex_adjust_prio(struct task_struct *task) |
| 302 | { |
| 303 | unsigned long flags; |
| 304 | |
| 305 | raw_spin_lock_irqsave(&task->pi_lock, flags); |
| 306 | __rt_mutex_adjust_prio(task); |
| 307 | raw_spin_unlock_irqrestore(&task->pi_lock, flags); |
| 308 | } |
| 309 | |
| 310 | /* |
| 311 | * Deadlock detection is conditional: |
| 312 | * |
| 313 | * If CONFIG_DEBUG_RT_MUTEXES=n, deadlock detection is only conducted |
| 314 | * if the detect argument is == RT_MUTEX_FULL_CHAINWALK. |
| 315 | * |
| 316 | * If CONFIG_DEBUG_RT_MUTEXES=y, deadlock detection is always |
| 317 | * conducted independent of the detect argument. |
| 318 | * |
| 319 | * If the waiter argument is NULL this indicates the deboost path and |
| 320 | * deadlock detection is disabled independent of the detect argument |
| 321 | * and the config settings. |
| 322 | */ |
| 323 | static bool rt_mutex_cond_detect_deadlock(struct rt_mutex_waiter *waiter, |
| 324 | enum rtmutex_chainwalk chwalk) |
| 325 | { |
| 326 | /* |
| 327 | * This is just a wrapper function for the following call, |
| 328 | * because debug_rt_mutex_detect_deadlock() smells like a magic |
| 329 | * debug feature and I wanted to keep the cond function in the |
| 330 | * main source file along with the comments instead of having |
| 331 | * two of the same in the headers. |
| 332 | */ |
| 333 | return debug_rt_mutex_detect_deadlock(waiter, chwalk); |
| 334 | } |
| 335 | |
| 336 | /* |
| 337 | * Max number of times we'll walk the boosting chain: |
| 338 | */ |
| 339 | int max_lock_depth = 1024; |
| 340 | |
| 341 | static inline struct rt_mutex *task_blocked_on_lock(struct task_struct *p) |
| 342 | { |
| 343 | return p->pi_blocked_on ? p->pi_blocked_on->lock : NULL; |
| 344 | } |
| 345 | |
| 346 | /* |
| 347 | * Adjust the priority chain. Also used for deadlock detection. |
| 348 | * Decreases task's usage by one - may thus free the task. |
| 349 | * |
| 350 | * @task: the task owning the mutex (owner) for which a chain walk is |
| 351 | * probably needed |
| 352 | * @deadlock_detect: do we have to carry out deadlock detection? |
| 353 | * @orig_lock: the mutex (can be NULL if we are walking the chain to recheck |
| 354 | * things for a task that has just got its priority adjusted, and |
| 355 | * is waiting on a mutex) |
| 356 | * @next_lock: the mutex on which the owner of @orig_lock was blocked before |
| 357 | * we dropped its pi_lock. Is never dereferenced, only used for |
| 358 | * comparison to detect lock chain changes. |
| 359 | * @orig_waiter: rt_mutex_waiter struct for the task that has just donated |
| 360 | * its priority to the mutex owner (can be NULL in the case |
| 361 | * depicted above or if the top waiter is gone away and we are |
| 362 | * actually deboosting the owner) |
| 363 | * @top_task: the current top waiter |
| 364 | * |
| 365 | * Returns 0 or -EDEADLK. |
| 366 | * |
| 367 | * Chain walk basics and protection scope |
| 368 | * |
| 369 | * [R] refcount on task |
| 370 | * [P] task->pi_lock held |
| 371 | * [L] rtmutex->wait_lock held |
| 372 | * |
| 373 | * Step Description Protected by |
| 374 | * function arguments: |
| 375 | * @task [R] |
| 376 | * @orig_lock if != NULL @top_task is blocked on it |
| 377 | * @next_lock Unprotected. Cannot be |
| 378 | * dereferenced. Only used for |
| 379 | * comparison. |
| 380 | * @orig_waiter if != NULL @top_task is blocked on it |
| 381 | * @top_task current, or in case of proxy |
| 382 | * locking protected by calling |
| 383 | * code |
| 384 | * again: |
| 385 | * loop_sanity_check(); |
| 386 | * retry: |
| 387 | * [1] lock(task->pi_lock); [R] acquire [P] |
| 388 | * [2] waiter = task->pi_blocked_on; [P] |
| 389 | * [3] check_exit_conditions_1(); [P] |
| 390 | * [4] lock = waiter->lock; [P] |
| 391 | * [5] if (!try_lock(lock->wait_lock)) { [P] try to acquire [L] |
| 392 | * unlock(task->pi_lock); release [P] |
| 393 | * goto retry; |
| 394 | * } |
| 395 | * [6] check_exit_conditions_2(); [P] + [L] |
| 396 | * [7] requeue_lock_waiter(lock, waiter); [P] + [L] |
| 397 | * [8] unlock(task->pi_lock); release [P] |
| 398 | * put_task_struct(task); release [R] |
| 399 | * [9] check_exit_conditions_3(); [L] |
| 400 | * [10] task = owner(lock); [L] |
| 401 | * get_task_struct(task); [L] acquire [R] |
| 402 | * lock(task->pi_lock); [L] acquire [P] |
| 403 | * [11] requeue_pi_waiter(tsk, waiters(lock));[P] + [L] |
| 404 | * [12] check_exit_conditions_4(); [P] + [L] |
| 405 | * [13] unlock(task->pi_lock); release [P] |
| 406 | * unlock(lock->wait_lock); release [L] |
| 407 | * goto again; |
| 408 | */ |
| 409 | static int rt_mutex_adjust_prio_chain(struct task_struct *task, |
| 410 | enum rtmutex_chainwalk chwalk, |
| 411 | struct rt_mutex *orig_lock, |
| 412 | struct rt_mutex *next_lock, |
| 413 | struct rt_mutex_waiter *orig_waiter, |
| 414 | struct task_struct *top_task) |
| 415 | { |
| 416 | struct rt_mutex_waiter *waiter, *top_waiter = orig_waiter; |
| 417 | struct rt_mutex_waiter *prerequeue_top_waiter; |
| 418 | int ret = 0, depth = 0; |
| 419 | struct rt_mutex *lock; |
| 420 | bool detect_deadlock; |
| 421 | unsigned long flags; |
| 422 | bool requeue = true; |
| 423 | |
| 424 | detect_deadlock = rt_mutex_cond_detect_deadlock(orig_waiter, chwalk); |
| 425 | |
| 426 | /* |
| 427 | * The (de)boosting is a step by step approach with a lot of |
| 428 | * pitfalls. We want this to be preemptible and we want hold a |
| 429 | * maximum of two locks per step. So we have to check |
| 430 | * carefully whether things change under us. |
| 431 | */ |
| 432 | again: |
| 433 | /* |
| 434 | * We limit the lock chain length for each invocation. |
| 435 | */ |
| 436 | if (++depth > max_lock_depth) { |
| 437 | static int prev_max; |
| 438 | |
| 439 | /* |
| 440 | * Print this only once. If the admin changes the limit, |
| 441 | * print a new message when reaching the limit again. |
| 442 | */ |
| 443 | if (prev_max != max_lock_depth) { |
| 444 | prev_max = max_lock_depth; |
| 445 | printk(KERN_WARNING "Maximum lock depth %d reached " |
| 446 | "task: %s (%d)\n", max_lock_depth, |
| 447 | top_task->comm, task_pid_nr(top_task)); |
| 448 | } |
| 449 | put_task_struct(task); |
| 450 | |
| 451 | return -EDEADLK; |
| 452 | } |
| 453 | |
| 454 | /* |
| 455 | * We are fully preemptible here and only hold the refcount on |
| 456 | * @task. So everything can have changed under us since the |
| 457 | * caller or our own code below (goto retry/again) dropped all |
| 458 | * locks. |
| 459 | */ |
| 460 | retry: |
| 461 | /* |
| 462 | * [1] Task cannot go away as we did a get_task() before ! |
| 463 | */ |
| 464 | raw_spin_lock_irqsave(&task->pi_lock, flags); |
| 465 | |
| 466 | /* |
| 467 | * [2] Get the waiter on which @task is blocked on. |
| 468 | */ |
| 469 | waiter = task->pi_blocked_on; |
| 470 | |
| 471 | /* |
| 472 | * [3] check_exit_conditions_1() protected by task->pi_lock. |
| 473 | */ |
| 474 | |
| 475 | /* |
| 476 | * Check whether the end of the boosting chain has been |
| 477 | * reached or the state of the chain has changed while we |
| 478 | * dropped the locks. |
| 479 | */ |
| 480 | if (!waiter) |
| 481 | goto out_unlock_pi; |
| 482 | |
| 483 | /* |
| 484 | * Check the orig_waiter state. After we dropped the locks, |
| 485 | * the previous owner of the lock might have released the lock. |
| 486 | */ |
| 487 | if (orig_waiter && !rt_mutex_owner(orig_lock)) |
| 488 | goto out_unlock_pi; |
| 489 | |
| 490 | /* |
| 491 | * We dropped all locks after taking a refcount on @task, so |
| 492 | * the task might have moved on in the lock chain or even left |
| 493 | * the chain completely and blocks now on an unrelated lock or |
| 494 | * on @orig_lock. |
| 495 | * |
| 496 | * We stored the lock on which @task was blocked in @next_lock, |
| 497 | * so we can detect the chain change. |
| 498 | */ |
| 499 | if (next_lock != waiter->lock) |
| 500 | goto out_unlock_pi; |
| 501 | |
| 502 | /* |
| 503 | * Drop out, when the task has no waiters. Note, |
| 504 | * top_waiter can be NULL, when we are in the deboosting |
| 505 | * mode! |
| 506 | */ |
| 507 | if (top_waiter) { |
| 508 | if (!task_has_pi_waiters(task)) |
| 509 | goto out_unlock_pi; |
| 510 | /* |
| 511 | * If deadlock detection is off, we stop here if we |
| 512 | * are not the top pi waiter of the task. If deadlock |
| 513 | * detection is enabled we continue, but stop the |
| 514 | * requeueing in the chain walk. |
| 515 | */ |
| 516 | if (top_waiter != task_top_pi_waiter(task)) { |
| 517 | if (!detect_deadlock) |
| 518 | goto out_unlock_pi; |
| 519 | else |
| 520 | requeue = false; |
| 521 | } |
| 522 | } |
| 523 | |
| 524 | /* |
| 525 | * If the waiter priority is the same as the task priority |
| 526 | * then there is no further priority adjustment necessary. If |
| 527 | * deadlock detection is off, we stop the chain walk. If its |
| 528 | * enabled we continue, but stop the requeueing in the chain |
| 529 | * walk. |
| 530 | */ |
| 531 | if (waiter->prio == task->prio) { |
| 532 | if (!detect_deadlock) |
| 533 | goto out_unlock_pi; |
| 534 | else |
| 535 | requeue = false; |
| 536 | } |
| 537 | |
| 538 | /* |
| 539 | * [4] Get the next lock |
| 540 | */ |
| 541 | lock = waiter->lock; |
| 542 | /* |
| 543 | * [5] We need to trylock here as we are holding task->pi_lock, |
| 544 | * which is the reverse lock order versus the other rtmutex |
| 545 | * operations. |
| 546 | */ |
| 547 | if (!raw_spin_trylock(&lock->wait_lock)) { |
| 548 | raw_spin_unlock_irqrestore(&task->pi_lock, flags); |
| 549 | cpu_relax(); |
| 550 | goto retry; |
| 551 | } |
| 552 | |
| 553 | /* |
| 554 | * [6] check_exit_conditions_2() protected by task->pi_lock and |
| 555 | * lock->wait_lock. |
| 556 | * |
| 557 | * Deadlock detection. If the lock is the same as the original |
| 558 | * lock which caused us to walk the lock chain or if the |
| 559 | * current lock is owned by the task which initiated the chain |
| 560 | * walk, we detected a deadlock. |
| 561 | */ |
| 562 | if (lock == orig_lock || rt_mutex_owner(lock) == top_task) { |
| 563 | debug_rt_mutex_deadlock(chwalk, orig_waiter, lock); |
| 564 | raw_spin_unlock(&lock->wait_lock); |
| 565 | ret = -EDEADLK; |
| 566 | goto out_unlock_pi; |
| 567 | } |
| 568 | |
| 569 | /* |
| 570 | * If we just follow the lock chain for deadlock detection, no |
| 571 | * need to do all the requeue operations. To avoid a truckload |
| 572 | * of conditionals around the various places below, just do the |
| 573 | * minimum chain walk checks. |
| 574 | */ |
| 575 | if (!requeue) { |
| 576 | /* |
| 577 | * No requeue[7] here. Just release @task [8] |
| 578 | */ |
| 579 | raw_spin_unlock_irqrestore(&task->pi_lock, flags); |
| 580 | put_task_struct(task); |
| 581 | |
| 582 | /* |
| 583 | * [9] check_exit_conditions_3 protected by lock->wait_lock. |
| 584 | * If there is no owner of the lock, end of chain. |
| 585 | */ |
| 586 | if (!rt_mutex_owner(lock)) { |
| 587 | raw_spin_unlock(&lock->wait_lock); |
| 588 | return 0; |
| 589 | } |
| 590 | |
| 591 | /* [10] Grab the next task, i.e. owner of @lock */ |
| 592 | task = rt_mutex_owner(lock); |
| 593 | get_task_struct(task); |
| 594 | raw_spin_lock_irqsave(&task->pi_lock, flags); |
| 595 | |
| 596 | /* |
| 597 | * No requeue [11] here. We just do deadlock detection. |
| 598 | * |
| 599 | * [12] Store whether owner is blocked |
| 600 | * itself. Decision is made after dropping the locks |
| 601 | */ |
| 602 | next_lock = task_blocked_on_lock(task); |
| 603 | /* |
| 604 | * Get the top waiter for the next iteration |
| 605 | */ |
| 606 | top_waiter = rt_mutex_top_waiter(lock); |
| 607 | |
| 608 | /* [13] Drop locks */ |
| 609 | raw_spin_unlock_irqrestore(&task->pi_lock, flags); |
| 610 | raw_spin_unlock(&lock->wait_lock); |
| 611 | |
| 612 | /* If owner is not blocked, end of chain. */ |
| 613 | if (!next_lock) |
| 614 | goto out_put_task; |
| 615 | goto again; |
| 616 | } |
| 617 | |
| 618 | /* |
| 619 | * Store the current top waiter before doing the requeue |
| 620 | * operation on @lock. We need it for the boost/deboost |
| 621 | * decision below. |
| 622 | */ |
| 623 | prerequeue_top_waiter = rt_mutex_top_waiter(lock); |
| 624 | |
| 625 | /* [7] Requeue the waiter in the lock waiter list. */ |
| 626 | rt_mutex_dequeue(lock, waiter); |
| 627 | waiter->prio = task->prio; |
| 628 | rt_mutex_enqueue(lock, waiter); |
| 629 | |
| 630 | /* [8] Release the task */ |
| 631 | raw_spin_unlock_irqrestore(&task->pi_lock, flags); |
| 632 | put_task_struct(task); |
| 633 | |
| 634 | /* |
| 635 | * [9] check_exit_conditions_3 protected by lock->wait_lock. |
| 636 | * |
| 637 | * We must abort the chain walk if there is no lock owner even |
| 638 | * in the dead lock detection case, as we have nothing to |
| 639 | * follow here. This is the end of the chain we are walking. |
| 640 | */ |
| 641 | if (!rt_mutex_owner(lock)) { |
| 642 | /* |
| 643 | * If the requeue [7] above changed the top waiter, |
| 644 | * then we need to wake the new top waiter up to try |
| 645 | * to get the lock. |
| 646 | */ |
| 647 | if (prerequeue_top_waiter != rt_mutex_top_waiter(lock)) |
| 648 | wake_up_process(rt_mutex_top_waiter(lock)->task); |
| 649 | raw_spin_unlock(&lock->wait_lock); |
| 650 | return 0; |
| 651 | } |
| 652 | |
| 653 | /* [10] Grab the next task, i.e. the owner of @lock */ |
| 654 | task = rt_mutex_owner(lock); |
| 655 | get_task_struct(task); |
| 656 | raw_spin_lock_irqsave(&task->pi_lock, flags); |
| 657 | |
| 658 | /* [11] requeue the pi waiters if necessary */ |
| 659 | if (waiter == rt_mutex_top_waiter(lock)) { |
| 660 | /* |
| 661 | * The waiter became the new top (highest priority) |
| 662 | * waiter on the lock. Replace the previous top waiter |
| 663 | * in the owner tasks pi waiters list with this waiter |
| 664 | * and adjust the priority of the owner. |
| 665 | */ |
| 666 | rt_mutex_dequeue_pi(task, prerequeue_top_waiter); |
| 667 | rt_mutex_enqueue_pi(task, waiter); |
| 668 | __rt_mutex_adjust_prio(task); |
| 669 | |
| 670 | } else if (prerequeue_top_waiter == waiter) { |
| 671 | /* |
| 672 | * The waiter was the top waiter on the lock, but is |
| 673 | * no longer the top prority waiter. Replace waiter in |
| 674 | * the owner tasks pi waiters list with the new top |
| 675 | * (highest priority) waiter and adjust the priority |
| 676 | * of the owner. |
| 677 | * The new top waiter is stored in @waiter so that |
| 678 | * @waiter == @top_waiter evaluates to true below and |
| 679 | * we continue to deboost the rest of the chain. |
| 680 | */ |
| 681 | rt_mutex_dequeue_pi(task, waiter); |
| 682 | waiter = rt_mutex_top_waiter(lock); |
| 683 | rt_mutex_enqueue_pi(task, waiter); |
| 684 | __rt_mutex_adjust_prio(task); |
| 685 | } else { |
| 686 | /* |
| 687 | * Nothing changed. No need to do any priority |
| 688 | * adjustment. |
| 689 | */ |
| 690 | } |
| 691 | |
| 692 | /* |
| 693 | * [12] check_exit_conditions_4() protected by task->pi_lock |
| 694 | * and lock->wait_lock. The actual decisions are made after we |
| 695 | * dropped the locks. |
| 696 | * |
| 697 | * Check whether the task which owns the current lock is pi |
| 698 | * blocked itself. If yes we store a pointer to the lock for |
| 699 | * the lock chain change detection above. After we dropped |
| 700 | * task->pi_lock next_lock cannot be dereferenced anymore. |
| 701 | */ |
| 702 | next_lock = task_blocked_on_lock(task); |
| 703 | /* |
| 704 | * Store the top waiter of @lock for the end of chain walk |
| 705 | * decision below. |
| 706 | */ |
| 707 | top_waiter = rt_mutex_top_waiter(lock); |
| 708 | |
| 709 | /* [13] Drop the locks */ |
| 710 | raw_spin_unlock_irqrestore(&task->pi_lock, flags); |
| 711 | raw_spin_unlock(&lock->wait_lock); |
| 712 | |
| 713 | /* |
| 714 | * Make the actual exit decisions [12], based on the stored |
| 715 | * values. |
| 716 | * |
| 717 | * We reached the end of the lock chain. Stop right here. No |
| 718 | * point to go back just to figure that out. |
| 719 | */ |
| 720 | if (!next_lock) |
| 721 | goto out_put_task; |
| 722 | |
| 723 | /* |
| 724 | * If the current waiter is not the top waiter on the lock, |
| 725 | * then we can stop the chain walk here if we are not in full |
| 726 | * deadlock detection mode. |
| 727 | */ |
| 728 | if (!detect_deadlock && waiter != top_waiter) |
| 729 | goto out_put_task; |
| 730 | |
| 731 | goto again; |
| 732 | |
| 733 | out_unlock_pi: |
| 734 | raw_spin_unlock_irqrestore(&task->pi_lock, flags); |
| 735 | out_put_task: |
| 736 | put_task_struct(task); |
| 737 | |
| 738 | return ret; |
| 739 | } |
| 740 | |
| 741 | /* |
| 742 | * Try to take an rt-mutex |
| 743 | * |
| 744 | * Must be called with lock->wait_lock held. |
| 745 | * |
| 746 | * @lock: The lock to be acquired. |
| 747 | * @task: The task which wants to acquire the lock |
| 748 | * @waiter: The waiter that is queued to the lock's wait list if the |
| 749 | * callsite called task_blocked_on_lock(), otherwise NULL |
| 750 | */ |
| 751 | static int try_to_take_rt_mutex(struct rt_mutex *lock, struct task_struct *task, |
| 752 | struct rt_mutex_waiter *waiter) |
| 753 | { |
| 754 | unsigned long flags; |
| 755 | |
| 756 | /* |
| 757 | * Before testing whether we can acquire @lock, we set the |
| 758 | * RT_MUTEX_HAS_WAITERS bit in @lock->owner. This forces all |
| 759 | * other tasks which try to modify @lock into the slow path |
| 760 | * and they serialize on @lock->wait_lock. |
| 761 | * |
| 762 | * The RT_MUTEX_HAS_WAITERS bit can have a transitional state |
| 763 | * as explained at the top of this file if and only if: |
| 764 | * |
| 765 | * - There is a lock owner. The caller must fixup the |
| 766 | * transient state if it does a trylock or leaves the lock |
| 767 | * function due to a signal or timeout. |
| 768 | * |
| 769 | * - @task acquires the lock and there are no other |
| 770 | * waiters. This is undone in rt_mutex_set_owner(@task) at |
| 771 | * the end of this function. |
| 772 | */ |
| 773 | mark_rt_mutex_waiters(lock); |
| 774 | |
| 775 | /* |
| 776 | * If @lock has an owner, give up. |
| 777 | */ |
| 778 | if (rt_mutex_owner(lock)) |
| 779 | return 0; |
| 780 | |
| 781 | /* |
| 782 | * If @waiter != NULL, @task has already enqueued the waiter |
| 783 | * into @lock waiter list. If @waiter == NULL then this is a |
| 784 | * trylock attempt. |
| 785 | */ |
| 786 | if (waiter) { |
| 787 | /* |
| 788 | * If waiter is not the highest priority waiter of |
| 789 | * @lock, give up. |
| 790 | */ |
| 791 | if (waiter != rt_mutex_top_waiter(lock)) |
| 792 | return 0; |
| 793 | |
| 794 | /* |
| 795 | * We can acquire the lock. Remove the waiter from the |
| 796 | * lock waiters list. |
| 797 | */ |
| 798 | rt_mutex_dequeue(lock, waiter); |
| 799 | |
| 800 | } else { |
| 801 | /* |
| 802 | * If the lock has waiters already we check whether @task is |
| 803 | * eligible to take over the lock. |
| 804 | * |
| 805 | * If there are no other waiters, @task can acquire |
| 806 | * the lock. @task->pi_blocked_on is NULL, so it does |
| 807 | * not need to be dequeued. |
| 808 | */ |
| 809 | if (rt_mutex_has_waiters(lock)) { |
| 810 | /* |
| 811 | * If @task->prio is greater than or equal to |
| 812 | * the top waiter priority (kernel view), |
| 813 | * @task lost. |
| 814 | */ |
| 815 | if (task->prio >= rt_mutex_top_waiter(lock)->prio) |
| 816 | return 0; |
| 817 | |
| 818 | /* |
| 819 | * The current top waiter stays enqueued. We |
| 820 | * don't have to change anything in the lock |
| 821 | * waiters order. |
| 822 | */ |
| 823 | } else { |
| 824 | /* |
| 825 | * No waiters. Take the lock without the |
| 826 | * pi_lock dance.@task->pi_blocked_on is NULL |
| 827 | * and we have no waiters to enqueue in @task |
| 828 | * pi waiters list. |
| 829 | */ |
| 830 | goto takeit; |
| 831 | } |
| 832 | } |
| 833 | |
| 834 | /* |
| 835 | * Clear @task->pi_blocked_on. Requires protection by |
| 836 | * @task->pi_lock. Redundant operation for the @waiter == NULL |
| 837 | * case, but conditionals are more expensive than a redundant |
| 838 | * store. |
| 839 | */ |
| 840 | raw_spin_lock_irqsave(&task->pi_lock, flags); |
| 841 | task->pi_blocked_on = NULL; |
| 842 | /* |
| 843 | * Finish the lock acquisition. @task is the new owner. If |
| 844 | * other waiters exist we have to insert the highest priority |
| 845 | * waiter into @task->pi_waiters list. |
| 846 | */ |
| 847 | if (rt_mutex_has_waiters(lock)) |
| 848 | rt_mutex_enqueue_pi(task, rt_mutex_top_waiter(lock)); |
| 849 | raw_spin_unlock_irqrestore(&task->pi_lock, flags); |
| 850 | |
| 851 | takeit: |
| 852 | /* We got the lock. */ |
| 853 | debug_rt_mutex_lock(lock); |
| 854 | |
| 855 | /* |
| 856 | * This either preserves the RT_MUTEX_HAS_WAITERS bit if there |
| 857 | * are still waiters or clears it. |
| 858 | */ |
| 859 | rt_mutex_set_owner(lock, task); |
| 860 | |
| 861 | rt_mutex_deadlock_account_lock(lock, task); |
| 862 | |
| 863 | return 1; |
| 864 | } |
| 865 | |
| 866 | /* |
| 867 | * Task blocks on lock. |
| 868 | * |
| 869 | * Prepare waiter and propagate pi chain |
| 870 | * |
| 871 | * This must be called with lock->wait_lock held. |
| 872 | */ |
| 873 | static int task_blocks_on_rt_mutex(struct rt_mutex *lock, |
| 874 | struct rt_mutex_waiter *waiter, |
| 875 | struct task_struct *task, |
| 876 | enum rtmutex_chainwalk chwalk) |
| 877 | { |
| 878 | struct task_struct *owner = rt_mutex_owner(lock); |
| 879 | struct rt_mutex_waiter *top_waiter = waiter; |
| 880 | struct rt_mutex *next_lock; |
| 881 | int chain_walk = 0, res; |
| 882 | unsigned long flags; |
| 883 | |
| 884 | /* |
| 885 | * Early deadlock detection. We really don't want the task to |
| 886 | * enqueue on itself just to untangle the mess later. It's not |
| 887 | * only an optimization. We drop the locks, so another waiter |
| 888 | * can come in before the chain walk detects the deadlock. So |
| 889 | * the other will detect the deadlock and return -EDEADLOCK, |
| 890 | * which is wrong, as the other waiter is not in a deadlock |
| 891 | * situation. |
| 892 | */ |
| 893 | if (owner == task) |
| 894 | return -EDEADLK; |
| 895 | |
| 896 | raw_spin_lock_irqsave(&task->pi_lock, flags); |
| 897 | __rt_mutex_adjust_prio(task); |
| 898 | waiter->task = task; |
| 899 | waiter->lock = lock; |
| 900 | waiter->prio = task->prio; |
| 901 | |
| 902 | /* Get the top priority waiter on the lock */ |
| 903 | if (rt_mutex_has_waiters(lock)) |
| 904 | top_waiter = rt_mutex_top_waiter(lock); |
| 905 | rt_mutex_enqueue(lock, waiter); |
| 906 | |
| 907 | task->pi_blocked_on = waiter; |
| 908 | |
| 909 | raw_spin_unlock_irqrestore(&task->pi_lock, flags); |
| 910 | |
| 911 | if (!owner) |
| 912 | return 0; |
| 913 | |
| 914 | raw_spin_lock_irqsave(&owner->pi_lock, flags); |
| 915 | if (waiter == rt_mutex_top_waiter(lock)) { |
| 916 | rt_mutex_dequeue_pi(owner, top_waiter); |
| 917 | rt_mutex_enqueue_pi(owner, waiter); |
| 918 | |
| 919 | __rt_mutex_adjust_prio(owner); |
| 920 | if (owner->pi_blocked_on) |
| 921 | chain_walk = 1; |
| 922 | } else if (rt_mutex_cond_detect_deadlock(waiter, chwalk)) { |
| 923 | chain_walk = 1; |
| 924 | } |
| 925 | |
| 926 | /* Store the lock on which owner is blocked or NULL */ |
| 927 | next_lock = task_blocked_on_lock(owner); |
| 928 | |
| 929 | raw_spin_unlock_irqrestore(&owner->pi_lock, flags); |
| 930 | /* |
| 931 | * Even if full deadlock detection is on, if the owner is not |
| 932 | * blocked itself, we can avoid finding this out in the chain |
| 933 | * walk. |
| 934 | */ |
| 935 | if (!chain_walk || !next_lock) |
| 936 | return 0; |
| 937 | |
| 938 | /* |
| 939 | * The owner can't disappear while holding a lock, |
| 940 | * so the owner struct is protected by wait_lock. |
| 941 | * Gets dropped in rt_mutex_adjust_prio_chain()! |
| 942 | */ |
| 943 | get_task_struct(owner); |
| 944 | |
| 945 | raw_spin_unlock(&lock->wait_lock); |
| 946 | |
| 947 | res = rt_mutex_adjust_prio_chain(owner, chwalk, lock, |
| 948 | next_lock, waiter, task); |
| 949 | |
| 950 | raw_spin_lock(&lock->wait_lock); |
| 951 | |
| 952 | return res; |
| 953 | } |
| 954 | |
| 955 | /* |
| 956 | * Wake up the next waiter on the lock. |
| 957 | * |
| 958 | * Remove the top waiter from the current tasks pi waiter list and |
| 959 | * wake it up. |
| 960 | * |
| 961 | * Called with lock->wait_lock held. |
| 962 | */ |
| 963 | static void wakeup_next_waiter(struct rt_mutex *lock) |
| 964 | { |
| 965 | struct rt_mutex_waiter *waiter; |
| 966 | unsigned long flags; |
| 967 | |
| 968 | raw_spin_lock_irqsave(¤t->pi_lock, flags); |
| 969 | |
| 970 | waiter = rt_mutex_top_waiter(lock); |
| 971 | |
| 972 | /* |
| 973 | * Remove it from current->pi_waiters. We do not adjust a |
| 974 | * possible priority boost right now. We execute wakeup in the |
| 975 | * boosted mode and go back to normal after releasing |
| 976 | * lock->wait_lock. |
| 977 | */ |
| 978 | rt_mutex_dequeue_pi(current, waiter); |
| 979 | |
| 980 | /* |
| 981 | * As we are waking up the top waiter, and the waiter stays |
| 982 | * queued on the lock until it gets the lock, this lock |
| 983 | * obviously has waiters. Just set the bit here and this has |
| 984 | * the added benefit of forcing all new tasks into the |
| 985 | * slow path making sure no task of lower priority than |
| 986 | * the top waiter can steal this lock. |
| 987 | */ |
| 988 | lock->owner = (void *) RT_MUTEX_HAS_WAITERS; |
| 989 | |
| 990 | raw_spin_unlock_irqrestore(¤t->pi_lock, flags); |
| 991 | |
| 992 | /* |
| 993 | * It's safe to dereference waiter as it cannot go away as |
| 994 | * long as we hold lock->wait_lock. The waiter task needs to |
| 995 | * acquire it in order to dequeue the waiter. |
| 996 | */ |
| 997 | wake_up_process(waiter->task); |
| 998 | } |
| 999 | |
| 1000 | /* |
| 1001 | * Remove a waiter from a lock and give up |
| 1002 | * |
| 1003 | * Must be called with lock->wait_lock held and |
| 1004 | * have just failed to try_to_take_rt_mutex(). |
| 1005 | */ |
| 1006 | static void remove_waiter(struct rt_mutex *lock, |
| 1007 | struct rt_mutex_waiter *waiter) |
| 1008 | { |
| 1009 | bool is_top_waiter = (waiter == rt_mutex_top_waiter(lock)); |
| 1010 | struct task_struct *owner = rt_mutex_owner(lock); |
| 1011 | struct rt_mutex *next_lock; |
| 1012 | unsigned long flags; |
| 1013 | |
| 1014 | raw_spin_lock_irqsave(¤t->pi_lock, flags); |
| 1015 | rt_mutex_dequeue(lock, waiter); |
| 1016 | current->pi_blocked_on = NULL; |
| 1017 | raw_spin_unlock_irqrestore(¤t->pi_lock, flags); |
| 1018 | |
| 1019 | /* |
| 1020 | * Only update priority if the waiter was the highest priority |
| 1021 | * waiter of the lock and there is an owner to update. |
| 1022 | */ |
| 1023 | if (!owner || !is_top_waiter) |
| 1024 | return; |
| 1025 | |
| 1026 | raw_spin_lock_irqsave(&owner->pi_lock, flags); |
| 1027 | |
| 1028 | rt_mutex_dequeue_pi(owner, waiter); |
| 1029 | |
| 1030 | if (rt_mutex_has_waiters(lock)) |
| 1031 | rt_mutex_enqueue_pi(owner, rt_mutex_top_waiter(lock)); |
| 1032 | |
| 1033 | __rt_mutex_adjust_prio(owner); |
| 1034 | |
| 1035 | /* Store the lock on which owner is blocked or NULL */ |
| 1036 | next_lock = task_blocked_on_lock(owner); |
| 1037 | |
| 1038 | raw_spin_unlock_irqrestore(&owner->pi_lock, flags); |
| 1039 | |
| 1040 | /* |
| 1041 | * Don't walk the chain, if the owner task is not blocked |
| 1042 | * itself. |
| 1043 | */ |
| 1044 | if (!next_lock) |
| 1045 | return; |
| 1046 | |
| 1047 | /* gets dropped in rt_mutex_adjust_prio_chain()! */ |
| 1048 | get_task_struct(owner); |
| 1049 | |
| 1050 | raw_spin_unlock(&lock->wait_lock); |
| 1051 | |
| 1052 | rt_mutex_adjust_prio_chain(owner, RT_MUTEX_MIN_CHAINWALK, lock, |
| 1053 | next_lock, NULL, current); |
| 1054 | |
| 1055 | raw_spin_lock(&lock->wait_lock); |
| 1056 | } |
| 1057 | |
| 1058 | /* |
| 1059 | * Recheck the pi chain, in case we got a priority setting |
| 1060 | * |
| 1061 | * Called from sched_setscheduler |
| 1062 | */ |
| 1063 | void rt_mutex_adjust_pi(struct task_struct *task) |
| 1064 | { |
| 1065 | struct rt_mutex_waiter *waiter; |
| 1066 | struct rt_mutex *next_lock; |
| 1067 | unsigned long flags; |
| 1068 | |
| 1069 | raw_spin_lock_irqsave(&task->pi_lock, flags); |
| 1070 | |
| 1071 | waiter = task->pi_blocked_on; |
| 1072 | if (!waiter || (waiter->prio == task->prio && |
| 1073 | !dl_prio(task->prio))) { |
| 1074 | raw_spin_unlock_irqrestore(&task->pi_lock, flags); |
| 1075 | return; |
| 1076 | } |
| 1077 | next_lock = waiter->lock; |
| 1078 | raw_spin_unlock_irqrestore(&task->pi_lock, flags); |
| 1079 | |
| 1080 | /* gets dropped in rt_mutex_adjust_prio_chain()! */ |
| 1081 | get_task_struct(task); |
| 1082 | |
| 1083 | rt_mutex_adjust_prio_chain(task, RT_MUTEX_MIN_CHAINWALK, NULL, |
| 1084 | next_lock, NULL, task); |
| 1085 | } |
| 1086 | |
| 1087 | /** |
| 1088 | * __rt_mutex_slowlock() - Perform the wait-wake-try-to-take loop |
| 1089 | * @lock: the rt_mutex to take |
| 1090 | * @state: the state the task should block in (TASK_INTERRUPTIBLE |
| 1091 | * or TASK_UNINTERRUPTIBLE) |
| 1092 | * @timeout: the pre-initialized and started timer, or NULL for none |
| 1093 | * @waiter: the pre-initialized rt_mutex_waiter |
| 1094 | * |
| 1095 | * lock->wait_lock must be held by the caller. |
| 1096 | */ |
| 1097 | static int __sched |
| 1098 | __rt_mutex_slowlock(struct rt_mutex *lock, int state, |
| 1099 | struct hrtimer_sleeper *timeout, |
| 1100 | struct rt_mutex_waiter *waiter) |
| 1101 | { |
| 1102 | int ret = 0; |
| 1103 | |
| 1104 | for (;;) { |
| 1105 | /* Try to acquire the lock: */ |
| 1106 | if (try_to_take_rt_mutex(lock, current, waiter)) |
| 1107 | break; |
| 1108 | |
| 1109 | /* |
| 1110 | * TASK_INTERRUPTIBLE checks for signals and |
| 1111 | * timeout. Ignored otherwise. |
| 1112 | */ |
| 1113 | if (unlikely(state == TASK_INTERRUPTIBLE)) { |
| 1114 | /* Signal pending? */ |
| 1115 | if (signal_pending(current)) |
| 1116 | ret = -EINTR; |
| 1117 | if (timeout && !timeout->task) |
| 1118 | ret = -ETIMEDOUT; |
| 1119 | if (ret) |
| 1120 | break; |
| 1121 | } |
| 1122 | |
| 1123 | raw_spin_unlock(&lock->wait_lock); |
| 1124 | |
| 1125 | debug_rt_mutex_print_deadlock(waiter); |
| 1126 | |
| 1127 | schedule_rt_mutex(lock); |
| 1128 | |
| 1129 | raw_spin_lock(&lock->wait_lock); |
| 1130 | set_current_state(state); |
| 1131 | } |
| 1132 | |
| 1133 | return ret; |
| 1134 | } |
| 1135 | |
| 1136 | static void rt_mutex_handle_deadlock(int res, int detect_deadlock, |
| 1137 | struct rt_mutex_waiter *w) |
| 1138 | { |
| 1139 | /* |
| 1140 | * If the result is not -EDEADLOCK or the caller requested |
| 1141 | * deadlock detection, nothing to do here. |
| 1142 | */ |
| 1143 | if (res != -EDEADLOCK || detect_deadlock) |
| 1144 | return; |
| 1145 | |
| 1146 | /* |
| 1147 | * Yell lowdly and stop the task right here. |
| 1148 | */ |
| 1149 | rt_mutex_print_deadlock(w); |
| 1150 | while (1) { |
| 1151 | set_current_state(TASK_INTERRUPTIBLE); |
| 1152 | schedule(); |
| 1153 | } |
| 1154 | } |
| 1155 | |
| 1156 | /* |
| 1157 | * Slow path lock function: |
| 1158 | */ |
| 1159 | static int __sched |
| 1160 | rt_mutex_slowlock(struct rt_mutex *lock, int state, |
| 1161 | struct hrtimer_sleeper *timeout, |
| 1162 | enum rtmutex_chainwalk chwalk) |
| 1163 | { |
| 1164 | struct rt_mutex_waiter waiter; |
| 1165 | int ret = 0; |
| 1166 | |
| 1167 | debug_rt_mutex_init_waiter(&waiter); |
| 1168 | RB_CLEAR_NODE(&waiter.pi_tree_entry); |
| 1169 | RB_CLEAR_NODE(&waiter.tree_entry); |
| 1170 | |
| 1171 | raw_spin_lock(&lock->wait_lock); |
| 1172 | |
| 1173 | /* Try to acquire the lock again: */ |
| 1174 | if (try_to_take_rt_mutex(lock, current, NULL)) { |
| 1175 | raw_spin_unlock(&lock->wait_lock); |
| 1176 | return 0; |
| 1177 | } |
| 1178 | |
| 1179 | set_current_state(state); |
| 1180 | |
| 1181 | /* Setup the timer, when timeout != NULL */ |
| 1182 | if (unlikely(timeout)) { |
| 1183 | hrtimer_start_expires(&timeout->timer, HRTIMER_MODE_ABS); |
| 1184 | if (!hrtimer_active(&timeout->timer)) |
| 1185 | timeout->task = NULL; |
| 1186 | } |
| 1187 | |
| 1188 | ret = task_blocks_on_rt_mutex(lock, &waiter, current, chwalk); |
| 1189 | |
| 1190 | if (likely(!ret)) |
| 1191 | ret = __rt_mutex_slowlock(lock, state, timeout, &waiter); |
| 1192 | |
| 1193 | set_current_state(TASK_RUNNING); |
| 1194 | |
| 1195 | if (unlikely(ret)) { |
| 1196 | remove_waiter(lock, &waiter); |
| 1197 | rt_mutex_handle_deadlock(ret, chwalk, &waiter); |
| 1198 | } |
| 1199 | |
| 1200 | /* |
| 1201 | * try_to_take_rt_mutex() sets the waiter bit |
| 1202 | * unconditionally. We might have to fix that up. |
| 1203 | */ |
| 1204 | fixup_rt_mutex_waiters(lock); |
| 1205 | |
| 1206 | raw_spin_unlock(&lock->wait_lock); |
| 1207 | |
| 1208 | /* Remove pending timer: */ |
| 1209 | if (unlikely(timeout)) |
| 1210 | hrtimer_cancel(&timeout->timer); |
| 1211 | |
| 1212 | debug_rt_mutex_free_waiter(&waiter); |
| 1213 | |
| 1214 | return ret; |
| 1215 | } |
| 1216 | |
| 1217 | /* |
| 1218 | * Slow path try-lock function: |
| 1219 | */ |
| 1220 | static inline int rt_mutex_slowtrylock(struct rt_mutex *lock) |
| 1221 | { |
| 1222 | int ret; |
| 1223 | |
| 1224 | /* |
| 1225 | * If the lock already has an owner we fail to get the lock. |
| 1226 | * This can be done without taking the @lock->wait_lock as |
| 1227 | * it is only being read, and this is a trylock anyway. |
| 1228 | */ |
| 1229 | if (rt_mutex_owner(lock)) |
| 1230 | return 0; |
| 1231 | |
| 1232 | /* |
| 1233 | * The mutex has currently no owner. Lock the wait lock and |
| 1234 | * try to acquire the lock. |
| 1235 | */ |
| 1236 | raw_spin_lock(&lock->wait_lock); |
| 1237 | |
| 1238 | ret = try_to_take_rt_mutex(lock, current, NULL); |
| 1239 | |
| 1240 | /* |
| 1241 | * try_to_take_rt_mutex() sets the lock waiters bit |
| 1242 | * unconditionally. Clean this up. |
| 1243 | */ |
| 1244 | fixup_rt_mutex_waiters(lock); |
| 1245 | |
| 1246 | raw_spin_unlock(&lock->wait_lock); |
| 1247 | |
| 1248 | return ret; |
| 1249 | } |
| 1250 | |
| 1251 | /* |
| 1252 | * Slow path to release a rt-mutex: |
| 1253 | */ |
| 1254 | static void __sched |
| 1255 | rt_mutex_slowunlock(struct rt_mutex *lock) |
| 1256 | { |
| 1257 | raw_spin_lock(&lock->wait_lock); |
| 1258 | |
| 1259 | debug_rt_mutex_unlock(lock); |
| 1260 | |
| 1261 | rt_mutex_deadlock_account_unlock(current); |
| 1262 | |
| 1263 | /* |
| 1264 | * We must be careful here if the fast path is enabled. If we |
| 1265 | * have no waiters queued we cannot set owner to NULL here |
| 1266 | * because of: |
| 1267 | * |
| 1268 | * foo->lock->owner = NULL; |
| 1269 | * rtmutex_lock(foo->lock); <- fast path |
| 1270 | * free = atomic_dec_and_test(foo->refcnt); |
| 1271 | * rtmutex_unlock(foo->lock); <- fast path |
| 1272 | * if (free) |
| 1273 | * kfree(foo); |
| 1274 | * raw_spin_unlock(foo->lock->wait_lock); |
| 1275 | * |
| 1276 | * So for the fastpath enabled kernel: |
| 1277 | * |
| 1278 | * Nothing can set the waiters bit as long as we hold |
| 1279 | * lock->wait_lock. So we do the following sequence: |
| 1280 | * |
| 1281 | * owner = rt_mutex_owner(lock); |
| 1282 | * clear_rt_mutex_waiters(lock); |
| 1283 | * raw_spin_unlock(&lock->wait_lock); |
| 1284 | * if (cmpxchg(&lock->owner, owner, 0) == owner) |
| 1285 | * return; |
| 1286 | * goto retry; |
| 1287 | * |
| 1288 | * The fastpath disabled variant is simple as all access to |
| 1289 | * lock->owner is serialized by lock->wait_lock: |
| 1290 | * |
| 1291 | * lock->owner = NULL; |
| 1292 | * raw_spin_unlock(&lock->wait_lock); |
| 1293 | */ |
| 1294 | while (!rt_mutex_has_waiters(lock)) { |
| 1295 | /* Drops lock->wait_lock ! */ |
| 1296 | if (unlock_rt_mutex_safe(lock) == true) |
| 1297 | return; |
| 1298 | /* Relock the rtmutex and try again */ |
| 1299 | raw_spin_lock(&lock->wait_lock); |
| 1300 | } |
| 1301 | |
| 1302 | /* |
| 1303 | * The wakeup next waiter path does not suffer from the above |
| 1304 | * race. See the comments there. |
| 1305 | */ |
| 1306 | wakeup_next_waiter(lock); |
| 1307 | |
| 1308 | raw_spin_unlock(&lock->wait_lock); |
| 1309 | |
| 1310 | /* Undo pi boosting if necessary: */ |
| 1311 | rt_mutex_adjust_prio(current); |
| 1312 | } |
| 1313 | |
| 1314 | /* |
| 1315 | * debug aware fast / slowpath lock,trylock,unlock |
| 1316 | * |
| 1317 | * The atomic acquire/release ops are compiled away, when either the |
| 1318 | * architecture does not support cmpxchg or when debugging is enabled. |
| 1319 | */ |
| 1320 | static inline int |
| 1321 | rt_mutex_fastlock(struct rt_mutex *lock, int state, |
| 1322 | int (*slowfn)(struct rt_mutex *lock, int state, |
| 1323 | struct hrtimer_sleeper *timeout, |
| 1324 | enum rtmutex_chainwalk chwalk)) |
| 1325 | { |
| 1326 | if (likely(rt_mutex_cmpxchg(lock, NULL, current))) { |
| 1327 | rt_mutex_deadlock_account_lock(lock, current); |
| 1328 | return 0; |
| 1329 | } else |
| 1330 | return slowfn(lock, state, NULL, RT_MUTEX_MIN_CHAINWALK); |
| 1331 | } |
| 1332 | |
| 1333 | static inline int |
| 1334 | rt_mutex_timed_fastlock(struct rt_mutex *lock, int state, |
| 1335 | struct hrtimer_sleeper *timeout, |
| 1336 | enum rtmutex_chainwalk chwalk, |
| 1337 | int (*slowfn)(struct rt_mutex *lock, int state, |
| 1338 | struct hrtimer_sleeper *timeout, |
| 1339 | enum rtmutex_chainwalk chwalk)) |
| 1340 | { |
| 1341 | if (chwalk == RT_MUTEX_MIN_CHAINWALK && |
| 1342 | likely(rt_mutex_cmpxchg(lock, NULL, current))) { |
| 1343 | rt_mutex_deadlock_account_lock(lock, current); |
| 1344 | return 0; |
| 1345 | } else |
| 1346 | return slowfn(lock, state, timeout, chwalk); |
| 1347 | } |
| 1348 | |
| 1349 | static inline int |
| 1350 | rt_mutex_fasttrylock(struct rt_mutex *lock, |
| 1351 | int (*slowfn)(struct rt_mutex *lock)) |
| 1352 | { |
| 1353 | if (likely(rt_mutex_cmpxchg(lock, NULL, current))) { |
| 1354 | rt_mutex_deadlock_account_lock(lock, current); |
| 1355 | return 1; |
| 1356 | } |
| 1357 | return slowfn(lock); |
| 1358 | } |
| 1359 | |
| 1360 | static inline void |
| 1361 | rt_mutex_fastunlock(struct rt_mutex *lock, |
| 1362 | void (*slowfn)(struct rt_mutex *lock)) |
| 1363 | { |
| 1364 | if (likely(rt_mutex_cmpxchg(lock, current, NULL))) |
| 1365 | rt_mutex_deadlock_account_unlock(current); |
| 1366 | else |
| 1367 | slowfn(lock); |
| 1368 | } |
| 1369 | |
| 1370 | /** |
| 1371 | * rt_mutex_lock - lock a rt_mutex |
| 1372 | * |
| 1373 | * @lock: the rt_mutex to be locked |
| 1374 | */ |
| 1375 | void __sched rt_mutex_lock(struct rt_mutex *lock) |
| 1376 | { |
| 1377 | might_sleep(); |
| 1378 | |
| 1379 | rt_mutex_fastlock(lock, TASK_UNINTERRUPTIBLE, rt_mutex_slowlock); |
| 1380 | } |
| 1381 | EXPORT_SYMBOL_GPL(rt_mutex_lock); |
| 1382 | |
| 1383 | /** |
| 1384 | * rt_mutex_lock_interruptible - lock a rt_mutex interruptible |
| 1385 | * |
| 1386 | * @lock: the rt_mutex to be locked |
| 1387 | * |
| 1388 | * Returns: |
| 1389 | * 0 on success |
| 1390 | * -EINTR when interrupted by a signal |
| 1391 | */ |
| 1392 | int __sched rt_mutex_lock_interruptible(struct rt_mutex *lock) |
| 1393 | { |
| 1394 | might_sleep(); |
| 1395 | |
| 1396 | return rt_mutex_fastlock(lock, TASK_INTERRUPTIBLE, rt_mutex_slowlock); |
| 1397 | } |
| 1398 | EXPORT_SYMBOL_GPL(rt_mutex_lock_interruptible); |
| 1399 | |
| 1400 | /* |
| 1401 | * Futex variant with full deadlock detection. |
| 1402 | */ |
| 1403 | int rt_mutex_timed_futex_lock(struct rt_mutex *lock, |
| 1404 | struct hrtimer_sleeper *timeout) |
| 1405 | { |
| 1406 | might_sleep(); |
| 1407 | |
| 1408 | return rt_mutex_timed_fastlock(lock, TASK_INTERRUPTIBLE, timeout, |
| 1409 | RT_MUTEX_FULL_CHAINWALK, |
| 1410 | rt_mutex_slowlock); |
| 1411 | } |
| 1412 | |
| 1413 | /** |
| 1414 | * rt_mutex_timed_lock - lock a rt_mutex interruptible |
| 1415 | * the timeout structure is provided |
| 1416 | * by the caller |
| 1417 | * |
| 1418 | * @lock: the rt_mutex to be locked |
| 1419 | * @timeout: timeout structure or NULL (no timeout) |
| 1420 | * |
| 1421 | * Returns: |
| 1422 | * 0 on success |
| 1423 | * -EINTR when interrupted by a signal |
| 1424 | * -ETIMEDOUT when the timeout expired |
| 1425 | */ |
| 1426 | int |
| 1427 | rt_mutex_timed_lock(struct rt_mutex *lock, struct hrtimer_sleeper *timeout) |
| 1428 | { |
| 1429 | might_sleep(); |
| 1430 | |
| 1431 | return rt_mutex_timed_fastlock(lock, TASK_INTERRUPTIBLE, timeout, |
| 1432 | RT_MUTEX_MIN_CHAINWALK, |
| 1433 | rt_mutex_slowlock); |
| 1434 | } |
| 1435 | EXPORT_SYMBOL_GPL(rt_mutex_timed_lock); |
| 1436 | |
| 1437 | /** |
| 1438 | * rt_mutex_trylock - try to lock a rt_mutex |
| 1439 | * |
| 1440 | * @lock: the rt_mutex to be locked |
| 1441 | * |
| 1442 | * Returns 1 on success and 0 on contention |
| 1443 | */ |
| 1444 | int __sched rt_mutex_trylock(struct rt_mutex *lock) |
| 1445 | { |
| 1446 | return rt_mutex_fasttrylock(lock, rt_mutex_slowtrylock); |
| 1447 | } |
| 1448 | EXPORT_SYMBOL_GPL(rt_mutex_trylock); |
| 1449 | |
| 1450 | /** |
| 1451 | * rt_mutex_unlock - unlock a rt_mutex |
| 1452 | * |
| 1453 | * @lock: the rt_mutex to be unlocked |
| 1454 | */ |
| 1455 | void __sched rt_mutex_unlock(struct rt_mutex *lock) |
| 1456 | { |
| 1457 | rt_mutex_fastunlock(lock, rt_mutex_slowunlock); |
| 1458 | } |
| 1459 | EXPORT_SYMBOL_GPL(rt_mutex_unlock); |
| 1460 | |
| 1461 | /** |
| 1462 | * rt_mutex_destroy - mark a mutex unusable |
| 1463 | * @lock: the mutex to be destroyed |
| 1464 | * |
| 1465 | * This function marks the mutex uninitialized, and any subsequent |
| 1466 | * use of the mutex is forbidden. The mutex must not be locked when |
| 1467 | * this function is called. |
| 1468 | */ |
| 1469 | void rt_mutex_destroy(struct rt_mutex *lock) |
| 1470 | { |
| 1471 | WARN_ON(rt_mutex_is_locked(lock)); |
| 1472 | #ifdef CONFIG_DEBUG_RT_MUTEXES |
| 1473 | lock->magic = NULL; |
| 1474 | #endif |
| 1475 | } |
| 1476 | |
| 1477 | EXPORT_SYMBOL_GPL(rt_mutex_destroy); |
| 1478 | |
| 1479 | /** |
| 1480 | * __rt_mutex_init - initialize the rt lock |
| 1481 | * |
| 1482 | * @lock: the rt lock to be initialized |
| 1483 | * |
| 1484 | * Initialize the rt lock to unlocked state. |
| 1485 | * |
| 1486 | * Initializing of a locked rt lock is not allowed |
| 1487 | */ |
| 1488 | void __rt_mutex_init(struct rt_mutex *lock, const char *name) |
| 1489 | { |
| 1490 | lock->owner = NULL; |
| 1491 | raw_spin_lock_init(&lock->wait_lock); |
| 1492 | lock->waiters = RB_ROOT; |
| 1493 | lock->waiters_leftmost = NULL; |
| 1494 | |
| 1495 | debug_rt_mutex_init(lock, name); |
| 1496 | } |
| 1497 | EXPORT_SYMBOL_GPL(__rt_mutex_init); |
| 1498 | |
| 1499 | /** |
| 1500 | * rt_mutex_init_proxy_locked - initialize and lock a rt_mutex on behalf of a |
| 1501 | * proxy owner |
| 1502 | * |
| 1503 | * @lock: the rt_mutex to be locked |
| 1504 | * @proxy_owner:the task to set as owner |
| 1505 | * |
| 1506 | * No locking. Caller has to do serializing itself |
| 1507 | * Special API call for PI-futex support |
| 1508 | */ |
| 1509 | void rt_mutex_init_proxy_locked(struct rt_mutex *lock, |
| 1510 | struct task_struct *proxy_owner) |
| 1511 | { |
| 1512 | __rt_mutex_init(lock, NULL); |
| 1513 | debug_rt_mutex_proxy_lock(lock, proxy_owner); |
| 1514 | rt_mutex_set_owner(lock, proxy_owner); |
| 1515 | rt_mutex_deadlock_account_lock(lock, proxy_owner); |
| 1516 | } |
| 1517 | |
| 1518 | /** |
| 1519 | * rt_mutex_proxy_unlock - release a lock on behalf of owner |
| 1520 | * |
| 1521 | * @lock: the rt_mutex to be locked |
| 1522 | * |
| 1523 | * No locking. Caller has to do serializing itself |
| 1524 | * Special API call for PI-futex support |
| 1525 | */ |
| 1526 | void rt_mutex_proxy_unlock(struct rt_mutex *lock, |
| 1527 | struct task_struct *proxy_owner) |
| 1528 | { |
| 1529 | debug_rt_mutex_proxy_unlock(lock); |
| 1530 | rt_mutex_set_owner(lock, NULL); |
| 1531 | rt_mutex_deadlock_account_unlock(proxy_owner); |
| 1532 | } |
| 1533 | |
| 1534 | /** |
| 1535 | * rt_mutex_start_proxy_lock() - Start lock acquisition for another task |
| 1536 | * @lock: the rt_mutex to take |
| 1537 | * @waiter: the pre-initialized rt_mutex_waiter |
| 1538 | * @task: the task to prepare |
| 1539 | * |
| 1540 | * Returns: |
| 1541 | * 0 - task blocked on lock |
| 1542 | * 1 - acquired the lock for task, caller should wake it up |
| 1543 | * <0 - error |
| 1544 | * |
| 1545 | * Special API call for FUTEX_REQUEUE_PI support. |
| 1546 | */ |
| 1547 | int rt_mutex_start_proxy_lock(struct rt_mutex *lock, |
| 1548 | struct rt_mutex_waiter *waiter, |
| 1549 | struct task_struct *task) |
| 1550 | { |
| 1551 | int ret; |
| 1552 | |
| 1553 | raw_spin_lock(&lock->wait_lock); |
| 1554 | |
| 1555 | if (try_to_take_rt_mutex(lock, task, NULL)) { |
| 1556 | raw_spin_unlock(&lock->wait_lock); |
| 1557 | return 1; |
| 1558 | } |
| 1559 | |
| 1560 | /* We enforce deadlock detection for futexes */ |
| 1561 | ret = task_blocks_on_rt_mutex(lock, waiter, task, |
| 1562 | RT_MUTEX_FULL_CHAINWALK); |
| 1563 | |
| 1564 | if (ret && !rt_mutex_owner(lock)) { |
| 1565 | /* |
| 1566 | * Reset the return value. We might have |
| 1567 | * returned with -EDEADLK and the owner |
| 1568 | * released the lock while we were walking the |
| 1569 | * pi chain. Let the waiter sort it out. |
| 1570 | */ |
| 1571 | ret = 0; |
| 1572 | } |
| 1573 | |
| 1574 | if (unlikely(ret)) |
| 1575 | remove_waiter(lock, waiter); |
| 1576 | |
| 1577 | raw_spin_unlock(&lock->wait_lock); |
| 1578 | |
| 1579 | debug_rt_mutex_print_deadlock(waiter); |
| 1580 | |
| 1581 | return ret; |
| 1582 | } |
| 1583 | |
| 1584 | /** |
| 1585 | * rt_mutex_next_owner - return the next owner of the lock |
| 1586 | * |
| 1587 | * @lock: the rt lock query |
| 1588 | * |
| 1589 | * Returns the next owner of the lock or NULL |
| 1590 | * |
| 1591 | * Caller has to serialize against other accessors to the lock |
| 1592 | * itself. |
| 1593 | * |
| 1594 | * Special API call for PI-futex support |
| 1595 | */ |
| 1596 | struct task_struct *rt_mutex_next_owner(struct rt_mutex *lock) |
| 1597 | { |
| 1598 | if (!rt_mutex_has_waiters(lock)) |
| 1599 | return NULL; |
| 1600 | |
| 1601 | return rt_mutex_top_waiter(lock)->task; |
| 1602 | } |
| 1603 | |
| 1604 | /** |
| 1605 | * rt_mutex_finish_proxy_lock() - Complete lock acquisition |
| 1606 | * @lock: the rt_mutex we were woken on |
| 1607 | * @to: the timeout, null if none. hrtimer should already have |
| 1608 | * been started. |
| 1609 | * @waiter: the pre-initialized rt_mutex_waiter |
| 1610 | * |
| 1611 | * Complete the lock acquisition started our behalf by another thread. |
| 1612 | * |
| 1613 | * Returns: |
| 1614 | * 0 - success |
| 1615 | * <0 - error, one of -EINTR, -ETIMEDOUT |
| 1616 | * |
| 1617 | * Special API call for PI-futex requeue support |
| 1618 | */ |
| 1619 | int rt_mutex_finish_proxy_lock(struct rt_mutex *lock, |
| 1620 | struct hrtimer_sleeper *to, |
| 1621 | struct rt_mutex_waiter *waiter) |
| 1622 | { |
| 1623 | int ret; |
| 1624 | |
| 1625 | raw_spin_lock(&lock->wait_lock); |
| 1626 | |
| 1627 | set_current_state(TASK_INTERRUPTIBLE); |
| 1628 | |
| 1629 | ret = __rt_mutex_slowlock(lock, TASK_INTERRUPTIBLE, to, waiter); |
| 1630 | |
| 1631 | set_current_state(TASK_RUNNING); |
| 1632 | |
| 1633 | if (unlikely(ret)) |
| 1634 | remove_waiter(lock, waiter); |
| 1635 | |
| 1636 | /* |
| 1637 | * try_to_take_rt_mutex() sets the waiter bit unconditionally. We might |
| 1638 | * have to fix that up. |
| 1639 | */ |
| 1640 | fixup_rt_mutex_waiters(lock); |
| 1641 | |
| 1642 | raw_spin_unlock(&lock->wait_lock); |
| 1643 | |
| 1644 | return ret; |
| 1645 | } |