Ingo Molnar | 408894e | 2006-01-09 15:59:20 -0800 | [diff] [blame] | 1 | /* |
| 2 | * kernel/mutex-debug.c |
| 3 | * |
| 4 | * Debugging code for mutexes |
| 5 | * |
| 6 | * Started by Ingo Molnar: |
| 7 | * |
| 8 | * Copyright (C) 2004, 2005, 2006 Red Hat, Inc., Ingo Molnar <mingo@redhat.com> |
| 9 | * |
| 10 | * lock debugging, locking tree, deadlock detection started by: |
| 11 | * |
| 12 | * Copyright (C) 2004, LynuxWorks, Inc., Igor Manyilov, Bill Huey |
| 13 | * Released under the General Public License (GPL). |
| 14 | */ |
| 15 | #include <linux/mutex.h> |
| 16 | #include <linux/sched.h> |
| 17 | #include <linux/delay.h> |
| 18 | #include <linux/module.h> |
| 19 | #include <linux/spinlock.h> |
| 20 | #include <linux/kallsyms.h> |
| 21 | #include <linux/interrupt.h> |
| 22 | |
Ingo Molnar | 408894e | 2006-01-09 15:59:20 -0800 | [diff] [blame] | 23 | #include "mutex-debug.h" |
| 24 | |
| 25 | /* |
| 26 | * We need a global lock when we walk through the multi-process |
| 27 | * lock tree. Only used in the deadlock-debugging case. |
| 28 | */ |
| 29 | DEFINE_SPINLOCK(debug_mutex_lock); |
| 30 | |
| 31 | /* |
| 32 | * All locks held by all tasks, in a single global list: |
| 33 | */ |
| 34 | LIST_HEAD(debug_mutex_held_locks); |
| 35 | |
| 36 | /* |
| 37 | * In the debug case we carry the caller's instruction pointer into |
| 38 | * other functions, but we dont want the function argument overhead |
| 39 | * in the nondebug case - hence these macros: |
| 40 | */ |
| 41 | #define __IP_DECL__ , unsigned long ip |
| 42 | #define __IP__ , ip |
| 43 | #define __RET_IP__ , (unsigned long)__builtin_return_address(0) |
| 44 | |
| 45 | /* |
| 46 | * "mutex debugging enabled" flag. We turn it off when we detect |
| 47 | * the first problem because we dont want to recurse back |
| 48 | * into the tracing code when doing error printk or |
| 49 | * executing a BUG(): |
| 50 | */ |
| 51 | int debug_mutex_on = 1; |
| 52 | |
| 53 | static void printk_task(struct task_struct *p) |
| 54 | { |
| 55 | if (p) |
| 56 | printk("%16s:%5d [%p, %3d]", p->comm, p->pid, p, p->prio); |
| 57 | else |
| 58 | printk("<none>"); |
| 59 | } |
| 60 | |
| 61 | static void printk_ti(struct thread_info *ti) |
| 62 | { |
| 63 | if (ti) |
| 64 | printk_task(ti->task); |
| 65 | else |
| 66 | printk("<none>"); |
| 67 | } |
| 68 | |
| 69 | static void printk_task_short(struct task_struct *p) |
| 70 | { |
| 71 | if (p) |
| 72 | printk("%s/%d [%p, %3d]", p->comm, p->pid, p, p->prio); |
| 73 | else |
| 74 | printk("<none>"); |
| 75 | } |
| 76 | |
| 77 | static void printk_lock(struct mutex *lock, int print_owner) |
| 78 | { |
| 79 | printk(" [%p] {%s}\n", lock, lock->name); |
| 80 | |
| 81 | if (print_owner && lock->owner) { |
| 82 | printk(".. held by: "); |
| 83 | printk_ti(lock->owner); |
| 84 | printk("\n"); |
| 85 | } |
| 86 | if (lock->owner) { |
| 87 | printk("... acquired at: "); |
| 88 | print_symbol("%s\n", lock->acquire_ip); |
| 89 | } |
| 90 | } |
| 91 | |
| 92 | /* |
| 93 | * printk locks held by a task: |
| 94 | */ |
| 95 | static void show_task_locks(struct task_struct *p) |
| 96 | { |
| 97 | switch (p->state) { |
| 98 | case TASK_RUNNING: printk("R"); break; |
| 99 | case TASK_INTERRUPTIBLE: printk("S"); break; |
| 100 | case TASK_UNINTERRUPTIBLE: printk("D"); break; |
| 101 | case TASK_STOPPED: printk("T"); break; |
| 102 | case EXIT_ZOMBIE: printk("Z"); break; |
| 103 | case EXIT_DEAD: printk("X"); break; |
| 104 | default: printk("?"); break; |
| 105 | } |
| 106 | printk_task(p); |
| 107 | if (p->blocked_on) { |
| 108 | struct mutex *lock = p->blocked_on->lock; |
| 109 | |
| 110 | printk(" blocked on mutex:"); |
| 111 | printk_lock(lock, 1); |
| 112 | } else |
| 113 | printk(" (not blocked on mutex)\n"); |
| 114 | } |
| 115 | |
| 116 | /* |
| 117 | * printk all locks held in the system (if filter == NULL), |
| 118 | * or all locks belonging to a single task (if filter != NULL): |
| 119 | */ |
| 120 | void show_held_locks(struct task_struct *filter) |
| 121 | { |
| 122 | struct list_head *curr, *cursor = NULL; |
| 123 | struct mutex *lock; |
| 124 | struct thread_info *t; |
| 125 | unsigned long flags; |
| 126 | int count = 0; |
| 127 | |
| 128 | if (filter) { |
| 129 | printk("------------------------------\n"); |
| 130 | printk("| showing all locks held by: | ("); |
| 131 | printk_task_short(filter); |
| 132 | printk("):\n"); |
| 133 | printk("------------------------------\n"); |
| 134 | } else { |
| 135 | printk("---------------------------\n"); |
| 136 | printk("| showing all locks held: |\n"); |
| 137 | printk("---------------------------\n"); |
| 138 | } |
| 139 | |
| 140 | /* |
| 141 | * Play safe and acquire the global trace lock. We |
| 142 | * cannot printk with that lock held so we iterate |
| 143 | * very carefully: |
| 144 | */ |
| 145 | next: |
| 146 | debug_spin_lock_save(&debug_mutex_lock, flags); |
| 147 | list_for_each(curr, &debug_mutex_held_locks) { |
| 148 | if (cursor && curr != cursor) |
| 149 | continue; |
| 150 | lock = list_entry(curr, struct mutex, held_list); |
| 151 | t = lock->owner; |
| 152 | if (filter && (t != filter->thread_info)) |
| 153 | continue; |
| 154 | count++; |
| 155 | cursor = curr->next; |
| 156 | debug_spin_lock_restore(&debug_mutex_lock, flags); |
| 157 | |
| 158 | printk("\n#%03d: ", count); |
| 159 | printk_lock(lock, filter ? 0 : 1); |
| 160 | goto next; |
| 161 | } |
| 162 | debug_spin_lock_restore(&debug_mutex_lock, flags); |
| 163 | printk("\n"); |
| 164 | } |
| 165 | |
| 166 | void mutex_debug_show_all_locks(void) |
| 167 | { |
| 168 | struct task_struct *g, *p; |
| 169 | int count = 10; |
| 170 | int unlock = 1; |
| 171 | |
| 172 | printk("\nShowing all blocking locks in the system:\n"); |
| 173 | |
| 174 | /* |
| 175 | * Here we try to get the tasklist_lock as hard as possible, |
| 176 | * if not successful after 2 seconds we ignore it (but keep |
| 177 | * trying). This is to enable a debug printout even if a |
| 178 | * tasklist_lock-holding task deadlocks or crashes. |
| 179 | */ |
| 180 | retry: |
| 181 | if (!read_trylock(&tasklist_lock)) { |
| 182 | if (count == 10) |
| 183 | printk("hm, tasklist_lock locked, retrying... "); |
| 184 | if (count) { |
| 185 | count--; |
| 186 | printk(" #%d", 10-count); |
| 187 | mdelay(200); |
| 188 | goto retry; |
| 189 | } |
| 190 | printk(" ignoring it.\n"); |
| 191 | unlock = 0; |
| 192 | } |
| 193 | if (count != 10) |
| 194 | printk(" locked it.\n"); |
| 195 | |
| 196 | do_each_thread(g, p) { |
| 197 | show_task_locks(p); |
| 198 | if (!unlock) |
| 199 | if (read_trylock(&tasklist_lock)) |
| 200 | unlock = 1; |
| 201 | } while_each_thread(g, p); |
| 202 | |
| 203 | printk("\n"); |
| 204 | show_held_locks(NULL); |
| 205 | printk("=============================================\n\n"); |
| 206 | |
| 207 | if (unlock) |
| 208 | read_unlock(&tasklist_lock); |
| 209 | } |
| 210 | |
| 211 | static void report_deadlock(struct task_struct *task, struct mutex *lock, |
| 212 | struct mutex *lockblk, unsigned long ip) |
| 213 | { |
| 214 | printk("\n%s/%d is trying to acquire this lock:\n", |
| 215 | current->comm, current->pid); |
| 216 | printk_lock(lock, 1); |
| 217 | printk("... trying at: "); |
| 218 | print_symbol("%s\n", ip); |
| 219 | show_held_locks(current); |
| 220 | |
| 221 | if (lockblk) { |
| 222 | printk("but %s/%d is deadlocking current task %s/%d!\n\n", |
| 223 | task->comm, task->pid, current->comm, current->pid); |
| 224 | printk("\n%s/%d is blocked on this lock:\n", |
| 225 | task->comm, task->pid); |
| 226 | printk_lock(lockblk, 1); |
| 227 | |
| 228 | show_held_locks(task); |
| 229 | |
| 230 | printk("\n%s/%d's [blocked] stackdump:\n\n", |
| 231 | task->comm, task->pid); |
| 232 | show_stack(task, NULL); |
| 233 | } |
| 234 | |
| 235 | printk("\n%s/%d's [current] stackdump:\n\n", |
| 236 | current->comm, current->pid); |
| 237 | dump_stack(); |
| 238 | mutex_debug_show_all_locks(); |
| 239 | printk("[ turning off deadlock detection. Please report this. ]\n\n"); |
| 240 | local_irq_disable(); |
| 241 | } |
| 242 | |
| 243 | /* |
| 244 | * Recursively check for mutex deadlocks: |
| 245 | */ |
| 246 | static int check_deadlock(struct mutex *lock, int depth, |
| 247 | struct thread_info *ti, unsigned long ip) |
| 248 | { |
| 249 | struct mutex *lockblk; |
| 250 | struct task_struct *task; |
| 251 | |
| 252 | if (!debug_mutex_on) |
| 253 | return 0; |
| 254 | |
| 255 | ti = lock->owner; |
| 256 | if (!ti) |
| 257 | return 0; |
| 258 | |
| 259 | task = ti->task; |
| 260 | lockblk = NULL; |
| 261 | if (task->blocked_on) |
| 262 | lockblk = task->blocked_on->lock; |
| 263 | |
| 264 | /* Self-deadlock: */ |
| 265 | if (current == task) { |
| 266 | DEBUG_OFF(); |
| 267 | if (depth) |
| 268 | return 1; |
| 269 | printk("\n==========================================\n"); |
| 270 | printk( "[ BUG: lock recursion deadlock detected! |\n"); |
| 271 | printk( "------------------------------------------\n"); |
| 272 | report_deadlock(task, lock, NULL, ip); |
| 273 | return 0; |
| 274 | } |
| 275 | |
| 276 | /* Ugh, something corrupted the lock data structure? */ |
| 277 | if (depth > 20) { |
| 278 | DEBUG_OFF(); |
| 279 | printk("\n===========================================\n"); |
| 280 | printk( "[ BUG: infinite lock dependency detected!? |\n"); |
| 281 | printk( "-------------------------------------------\n"); |
| 282 | report_deadlock(task, lock, lockblk, ip); |
| 283 | return 0; |
| 284 | } |
| 285 | |
| 286 | /* Recursively check for dependencies: */ |
| 287 | if (lockblk && check_deadlock(lockblk, depth+1, ti, ip)) { |
| 288 | printk("\n============================================\n"); |
| 289 | printk( "[ BUG: circular locking deadlock detected! ]\n"); |
| 290 | printk( "--------------------------------------------\n"); |
| 291 | report_deadlock(task, lock, lockblk, ip); |
| 292 | return 0; |
| 293 | } |
| 294 | return 0; |
| 295 | } |
| 296 | |
| 297 | /* |
| 298 | * Called when a task exits, this function checks whether the |
| 299 | * task is holding any locks, and reports the first one if so: |
| 300 | */ |
| 301 | void mutex_debug_check_no_locks_held(struct task_struct *task) |
| 302 | { |
| 303 | struct list_head *curr, *next; |
| 304 | struct thread_info *t; |
| 305 | unsigned long flags; |
| 306 | struct mutex *lock; |
| 307 | |
| 308 | if (!debug_mutex_on) |
| 309 | return; |
| 310 | |
| 311 | debug_spin_lock_save(&debug_mutex_lock, flags); |
| 312 | list_for_each_safe(curr, next, &debug_mutex_held_locks) { |
| 313 | lock = list_entry(curr, struct mutex, held_list); |
| 314 | t = lock->owner; |
| 315 | if (t != task->thread_info) |
| 316 | continue; |
| 317 | list_del_init(curr); |
| 318 | DEBUG_OFF(); |
| 319 | debug_spin_lock_restore(&debug_mutex_lock, flags); |
| 320 | |
| 321 | printk("BUG: %s/%d, lock held at task exit time!\n", |
| 322 | task->comm, task->pid); |
| 323 | printk_lock(lock, 1); |
| 324 | if (lock->owner != task->thread_info) |
| 325 | printk("exiting task is not even the owner??\n"); |
| 326 | return; |
| 327 | } |
| 328 | debug_spin_lock_restore(&debug_mutex_lock, flags); |
| 329 | } |
| 330 | |
| 331 | /* |
| 332 | * Called when kernel memory is freed (or unmapped), or if a mutex |
| 333 | * is destroyed or reinitialized - this code checks whether there is |
| 334 | * any held lock in the memory range of <from> to <to>: |
| 335 | */ |
David Woodhouse | a4fc7ab | 2006-01-11 14:41:26 +0000 | [diff] [blame] | 336 | void mutex_debug_check_no_locks_freed(const void *from, unsigned long len) |
Ingo Molnar | 408894e | 2006-01-09 15:59:20 -0800 | [diff] [blame] | 337 | { |
| 338 | struct list_head *curr, *next; |
David Woodhouse | a4fc7ab | 2006-01-11 14:41:26 +0000 | [diff] [blame] | 339 | const void *to = from + len; |
Ingo Molnar | 408894e | 2006-01-09 15:59:20 -0800 | [diff] [blame] | 340 | unsigned long flags; |
| 341 | struct mutex *lock; |
| 342 | void *lock_addr; |
| 343 | |
| 344 | if (!debug_mutex_on) |
| 345 | return; |
| 346 | |
| 347 | debug_spin_lock_save(&debug_mutex_lock, flags); |
| 348 | list_for_each_safe(curr, next, &debug_mutex_held_locks) { |
| 349 | lock = list_entry(curr, struct mutex, held_list); |
| 350 | lock_addr = lock; |
| 351 | if (lock_addr < from || lock_addr >= to) |
| 352 | continue; |
| 353 | list_del_init(curr); |
| 354 | DEBUG_OFF(); |
| 355 | debug_spin_lock_restore(&debug_mutex_lock, flags); |
| 356 | |
| 357 | printk("BUG: %s/%d, active lock [%p(%p-%p)] freed!\n", |
| 358 | current->comm, current->pid, lock, from, to); |
| 359 | dump_stack(); |
| 360 | printk_lock(lock, 1); |
| 361 | if (lock->owner != current_thread_info()) |
| 362 | printk("freeing task is not even the owner??\n"); |
| 363 | return; |
| 364 | } |
| 365 | debug_spin_lock_restore(&debug_mutex_lock, flags); |
| 366 | } |
| 367 | |
| 368 | /* |
| 369 | * Must be called with lock->wait_lock held. |
| 370 | */ |
| 371 | void debug_mutex_set_owner(struct mutex *lock, |
| 372 | struct thread_info *new_owner __IP_DECL__) |
| 373 | { |
| 374 | lock->owner = new_owner; |
| 375 | DEBUG_WARN_ON(!list_empty(&lock->held_list)); |
| 376 | if (debug_mutex_on) { |
| 377 | list_add_tail(&lock->held_list, &debug_mutex_held_locks); |
| 378 | lock->acquire_ip = ip; |
| 379 | } |
| 380 | } |
| 381 | |
| 382 | void debug_mutex_init_waiter(struct mutex_waiter *waiter) |
| 383 | { |
| 384 | memset(waiter, 0x11, sizeof(*waiter)); |
| 385 | waiter->magic = waiter; |
| 386 | INIT_LIST_HEAD(&waiter->list); |
| 387 | } |
| 388 | |
| 389 | void debug_mutex_wake_waiter(struct mutex *lock, struct mutex_waiter *waiter) |
| 390 | { |
| 391 | SMP_DEBUG_WARN_ON(!spin_is_locked(&lock->wait_lock)); |
| 392 | DEBUG_WARN_ON(list_empty(&lock->wait_list)); |
| 393 | DEBUG_WARN_ON(waiter->magic != waiter); |
| 394 | DEBUG_WARN_ON(list_empty(&waiter->list)); |
| 395 | } |
| 396 | |
| 397 | void debug_mutex_free_waiter(struct mutex_waiter *waiter) |
| 398 | { |
| 399 | DEBUG_WARN_ON(!list_empty(&waiter->list)); |
| 400 | memset(waiter, 0x22, sizeof(*waiter)); |
| 401 | } |
| 402 | |
| 403 | void debug_mutex_add_waiter(struct mutex *lock, struct mutex_waiter *waiter, |
| 404 | struct thread_info *ti __IP_DECL__) |
| 405 | { |
| 406 | SMP_DEBUG_WARN_ON(!spin_is_locked(&lock->wait_lock)); |
| 407 | check_deadlock(lock, 0, ti, ip); |
| 408 | /* Mark the current thread as blocked on the lock: */ |
| 409 | ti->task->blocked_on = waiter; |
| 410 | waiter->lock = lock; |
| 411 | } |
| 412 | |
| 413 | void mutex_remove_waiter(struct mutex *lock, struct mutex_waiter *waiter, |
| 414 | struct thread_info *ti) |
| 415 | { |
| 416 | DEBUG_WARN_ON(list_empty(&waiter->list)); |
| 417 | DEBUG_WARN_ON(waiter->task != ti->task); |
| 418 | DEBUG_WARN_ON(ti->task->blocked_on != waiter); |
| 419 | ti->task->blocked_on = NULL; |
| 420 | |
| 421 | list_del_init(&waiter->list); |
| 422 | waiter->task = NULL; |
| 423 | } |
| 424 | |
| 425 | void debug_mutex_unlock(struct mutex *lock) |
| 426 | { |
| 427 | DEBUG_WARN_ON(lock->magic != lock); |
| 428 | DEBUG_WARN_ON(!lock->wait_list.prev && !lock->wait_list.next); |
| 429 | DEBUG_WARN_ON(lock->owner != current_thread_info()); |
| 430 | if (debug_mutex_on) { |
| 431 | DEBUG_WARN_ON(list_empty(&lock->held_list)); |
| 432 | list_del_init(&lock->held_list); |
| 433 | } |
| 434 | } |
| 435 | |
| 436 | void debug_mutex_init(struct mutex *lock, const char *name) |
| 437 | { |
| 438 | /* |
| 439 | * Make sure we are not reinitializing a held lock: |
| 440 | */ |
David Woodhouse | a4fc7ab | 2006-01-11 14:41:26 +0000 | [diff] [blame] | 441 | mutex_debug_check_no_locks_freed((void *)lock, sizeof(*lock)); |
Ingo Molnar | 408894e | 2006-01-09 15:59:20 -0800 | [diff] [blame] | 442 | lock->owner = NULL; |
| 443 | INIT_LIST_HEAD(&lock->held_list); |
| 444 | lock->name = name; |
| 445 | lock->magic = lock; |
| 446 | } |
| 447 | |
| 448 | /*** |
| 449 | * mutex_destroy - mark a mutex unusable |
| 450 | * @lock: the mutex to be destroyed |
| 451 | * |
| 452 | * This function marks the mutex uninitialized, and any subsequent |
| 453 | * use of the mutex is forbidden. The mutex must not be locked when |
| 454 | * this function is called. |
| 455 | */ |
| 456 | void fastcall mutex_destroy(struct mutex *lock) |
| 457 | { |
| 458 | DEBUG_WARN_ON(mutex_is_locked(lock)); |
| 459 | lock->magic = NULL; |
| 460 | } |
| 461 | |
| 462 | EXPORT_SYMBOL_GPL(mutex_destroy); |