kernel/rtmutex-debug.c

   1 /*
   2  * RT-Mutexes: 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) 2006 Timesys Corp., Thomas Gleixner <tglx@timesys.com>
   8  *
   9  * This code is based on the rt.c implementation in the preempt-rt tree.
  10  * Portions of said code are
  11  *
  12  *  Copyright (C) 2004  LynuxWorks, Inc., Igor Manyilov, Bill Huey
  13  *  Copyright (C) 2006  Esben Nielsen
  14  *  Copyright (C) 2006  Kihon Technologies Inc.,
  15  *                      Steven Rostedt <rostedt@goodmis.org>
  16  *
  17  * See rt.c in preempt-rt for proper credits and further information
  18  */
  19 #include <linux/config.h>
  20 #include <linux/sched.h>
  21 #include <linux/delay.h>
  22 #include <linux/module.h>
  23 #include <linux/spinlock.h>
  24 #include <linux/kallsyms.h>
  25 #include <linux/syscalls.h>
  26 #include <linux/interrupt.h>
  27 #include <linux/plist.h>
  28 #include <linux/fs.h>
  29
  30 #include "rtmutex_common.h"
  31
  32 #ifdef CONFIG_DEBUG_RT_MUTEXES
  33 # include "rtmutex-debug.h"
  34 #else
  35 # include "rtmutex.h"
  36 #endif
  37
  38 # define TRACE_WARN_ON(x)                       WARN_ON(x)
  39 # define TRACE_BUG_ON(x)                        BUG_ON(x)
  40
  41 # define TRACE_OFF()                                            \
  42 do {                                                            \
  43         if (rt_trace_on) {                                      \
  44                 rt_trace_on = 0;                                \
  45                 console_verbose();                              \
  46                 if (spin_is_locked(&current->pi_lock))          \
  47                         spin_unlock(&current->pi_lock);         \
  48                 if (spin_is_locked(&current->held_list_lock))   \
  49                         spin_unlock(&current->held_list_lock);  \
  50         }                                                       \
  51 } while (0)
  52
  53 # define TRACE_OFF_NOLOCK()                                     \
  54 do {                                                            \
  55         if (rt_trace_on) {                                      \
  56                 rt_trace_on = 0;                                \
  57                 console_verbose();                              \
  58         }                                                       \
  59 } while (0)
  60
  61 # define TRACE_BUG_LOCKED()                     \
  62 do {                                            \
  63         TRACE_OFF();                            \
  64         BUG();                                  \
  65 } while (0)
  66
  67 # define TRACE_WARN_ON_LOCKED(c)                \
  68 do {                                            \
  69         if (unlikely(c)) {                      \
  70                 TRACE_OFF();                    \
  71                 WARN_ON(1);                     \
  72         }                                       \
  73 } while (0)
  74
  75 # define TRACE_BUG_ON_LOCKED(c)                 \
  76 do {                                            \
  77         if (unlikely(c))                        \
  78                 TRACE_BUG_LOCKED();             \
  79 } while (0)
  80
  81 #ifdef CONFIG_SMP
  82 # define SMP_TRACE_BUG_ON_LOCKED(c)     TRACE_BUG_ON_LOCKED(c)
  83 #else
  84 # define SMP_TRACE_BUG_ON_LOCKED(c)     do { } while (0)
  85 #endif
  86
  87 /*
  88  * deadlock detection flag. We turn it off when we detect
  89  * the first problem because we dont want to recurse back
  90  * into the tracing code when doing error printk or
  91  * executing a BUG():
  92  */
  93 int rt_trace_on = 1;
  94
  95 void deadlock_trace_off(void)
  96 {
  97         rt_trace_on = 0;
  98 }
  99
 100 static void printk_task(task_t *p)
 101 {
 102         if (p)
 103                 printk("%16s:%5d [%p, %3d]", p->comm, p->pid, p, p->prio);
 104         else
 105                 printk("<none>");
 106 }
 107
 108 static void printk_task_short(task_t *p)
 109 {
 110         if (p)
 111                 printk("%s/%d [%p, %3d]", p->comm, p->pid, p, p->prio);
 112         else
 113                 printk("<none>");
 114 }
 115
 116 static void printk_lock(struct rt_mutex *lock, int print_owner)
 117 {
 118         if (lock->name)
 119                 printk(" [%p] {%s}\n",
 120                         lock, lock->name);
 121         else
 122                 printk(" [%p] {%s:%d}\n",
 123                         lock, lock->file, lock->line);
 124
 125         if (print_owner && rt_mutex_owner(lock)) {
 126                 printk(".. ->owner: %p\n", lock->owner);
 127                 printk(".. held by:  ");
 128                 printk_task(rt_mutex_owner(lock));
 129                 printk("\n");
 130         }
 131         if (rt_mutex_owner(lock)) {
 132                 printk("... acquired at:               ");
 133                 print_symbol("%s\n", lock->acquire_ip);
 134         }
 135 }
 136
 137 static void printk_waiter(struct rt_mutex_waiter *w)
 138 {
 139         printk("-------------------------\n");
 140         printk("| waiter struct %p:\n", w);
 141         printk("| w->list_entry: [DP:%p/%p|SP:%p/%p|PRI:%d]\n",
 142                w->list_entry.plist.prio_list.prev, w->list_entry.plist.prio_list.next,
 143                w->list_entry.plist.node_list.prev, w->list_entry.plist.node_list.next,
 144                w->list_entry.prio);
 145         printk("| w->pi_list_entry: [DP:%p/%p|SP:%p/%p|PRI:%d]\n",
 146                w->pi_list_entry.plist.prio_list.prev, w->pi_list_entry.plist.prio_list.next,
 147                w->pi_list_entry.plist.node_list.prev, w->pi_list_entry.plist.node_list.next,
 148                w->pi_list_entry.prio);
 149         printk("\n| lock:\n");
 150         printk_lock(w->lock, 1);
 151         printk("| w->ti->task:\n");
 152         printk_task(w->task);
 153         printk("| blocked at:  ");
 154         print_symbol("%s\n", w->ip);
 155         printk("-------------------------\n");
 156 }
 157
 158 static void show_task_locks(task_t *p)
 159 {
 160         switch (p->state) {
 161         case TASK_RUNNING:              printk("R"); break;
 162         case TASK_INTERRUPTIBLE:        printk("S"); break;
 163         case TASK_UNINTERRUPTIBLE:      printk("D"); break;
 164         case TASK_STOPPED:              printk("T"); break;
 165         case EXIT_ZOMBIE:               printk("Z"); break;
 166         case EXIT_DEAD:                 printk("X"); break;
 167         default:                        printk("?"); break;
 168         }
 169         printk_task(p);
 170         if (p->pi_blocked_on) {
 171                 struct rt_mutex *lock = p->pi_blocked_on->lock;
 172
 173                 printk(" blocked on:");
 174                 printk_lock(lock, 1);
 175         } else
 176                 printk(" (not blocked)\n");
 177 }
 178
 179 void rt_mutex_show_held_locks(task_t *task, int verbose)
 180 {
 181         struct list_head *curr, *cursor = NULL;
 182         struct rt_mutex *lock;
 183         task_t *t;
 184         unsigned long flags;
 185         int count = 0;
 186
 187         if (!rt_trace_on)
 188                 return;
 189
 190         if (verbose) {
 191                 printk("------------------------------\n");
 192                 printk("| showing all locks held by: |  (");
 193                 printk_task_short(task);
 194                 printk("):\n");
 195                 printk("------------------------------\n");
 196         }
 197
 198 next:
 199         spin_lock_irqsave(&task->held_list_lock, flags);
 200         list_for_each(curr, &task->held_list_head) {
 201                 if (cursor && curr != cursor)
 202                         continue;
 203                 lock = list_entry(curr, struct rt_mutex, held_list_entry);
 204                 t = rt_mutex_owner(lock);
 205                 WARN_ON(t != task);
 206                 count++;
 207                 cursor = curr->next;
 208                 spin_unlock_irqrestore(&task->held_list_lock, flags);
 209
 210                 printk("\n#%03d:            ", count);
 211                 printk_lock(lock, 0);
 212                 goto next;
 213         }
 214         spin_unlock_irqrestore(&task->held_list_lock, flags);
 215
 216         printk("\n");
 217 }
 218
 219 void rt_mutex_show_all_locks(void)
 220 {
 221         task_t *g, *p;
 222         int count = 10;
 223         int unlock = 1;
 224
 225         printk("\n");
 226         printk("----------------------\n");
 227         printk("| showing all tasks: |\n");
 228         printk("----------------------\n");
 229
 230         /*
 231          * Here we try to get the tasklist_lock as hard as possible,
 232          * if not successful after 2 seconds we ignore it (but keep
 233          * trying). This is to enable a debug printout even if a
 234          * tasklist_lock-holding task deadlocks or crashes.
 235          */
 236 retry:
 237         if (!read_trylock(&tasklist_lock)) {
 238                 if (count == 10)
 239                         printk("hm, tasklist_lock locked, retrying... ");
 240                 if (count) {
 241                         count--;
 242                         printk(" #%d", 10-count);
 243                         mdelay(200);
 244                         goto retry;
 245                 }
 246                 printk(" ignoring it.\n");
 247                 unlock = 0;
 248         }
 249         if (count != 10)
 250                 printk(" locked it.\n");
 251
 252         do_each_thread(g, p) {
 253                 show_task_locks(p);
 254                 if (!unlock)
 255                         if (read_trylock(&tasklist_lock))
 256                                 unlock = 1;
 257         } while_each_thread(g, p);
 258
 259         printk("\n");
 260
 261         printk("-----------------------------------------\n");
 262         printk("| showing all locks held in the system: |\n");
 263         printk("-----------------------------------------\n");
 264
 265         do_each_thread(g, p) {
 266                 rt_mutex_show_held_locks(p, 0);
 267                 if (!unlock)
 268                         if (read_trylock(&tasklist_lock))
 269                                 unlock = 1;
 270         } while_each_thread(g, p);
 271
 272
 273         printk("=============================================\n\n");
 274
 275         if (unlock)
 276                 read_unlock(&tasklist_lock);
 277 }
 278
 279 void rt_mutex_debug_check_no_locks_held(task_t *task)
 280 {
 281         struct rt_mutex_waiter *w;
 282         struct list_head *curr;
 283         struct rt_mutex *lock;
 284
 285         if (!rt_trace_on)
 286                 return;
 287         if (!rt_prio(task->normal_prio) && rt_prio(task->prio)) {
 288                 printk("BUG: PI priority boost leaked!\n");
 289                 printk_task(task);
 290                 printk("\n");
 291         }
 292         if (list_empty(&task->held_list_head))
 293                 return;
 294
 295         spin_lock(&task->pi_lock);
 296         plist_for_each_entry(w, &task->pi_waiters, pi_list_entry) {
 297                 TRACE_OFF();
 298
 299                 printk("hm, PI interest held at exit time? Task:\n");
 300                 printk_task(task);
 301                 printk_waiter(w);
 302                 return;
 303         }
 304         spin_unlock(&task->pi_lock);
 305
 306         list_for_each(curr, &task->held_list_head) {
 307                 lock = list_entry(curr, struct rt_mutex, held_list_entry);
 308
 309                 printk("BUG: %s/%d, lock held at task exit time!\n",
 310                        task->comm, task->pid);
 311                 printk_lock(lock, 1);
 312                 if (rt_mutex_owner(lock) != task)
 313                         printk("exiting task is not even the owner??\n");
 314         }
 315 }
 316
 317 int rt_mutex_debug_check_no_locks_freed(const void *from, unsigned long len)
 318 {
 319         const void *to = from + len;
 320         struct list_head *curr;
 321         struct rt_mutex *lock;
 322         unsigned long flags;
 323         void *lock_addr;
 324
 325         if (!rt_trace_on)
 326                 return 0;
 327
 328         spin_lock_irqsave(&current->held_list_lock, flags);
 329         list_for_each(curr, &current->held_list_head) {
 330                 lock = list_entry(curr, struct rt_mutex, held_list_entry);
 331                 lock_addr = lock;
 332                 if (lock_addr < from || lock_addr >= to)
 333                         continue;
 334                 TRACE_OFF();
 335
 336                 printk("BUG: %s/%d, active lock [%p(%p-%p)] freed!\n",
 337                         current->comm, current->pid, lock, from, to);
 338                 dump_stack();
 339                 printk_lock(lock, 1);
 340                 if (rt_mutex_owner(lock) != current)
 341                         printk("freeing task is not even the owner??\n");
 342                 return 1;
 343         }
 344         spin_unlock_irqrestore(&current->held_list_lock, flags);
 345
 346         return 0;
 347 }
 348
 349 void rt_mutex_debug_task_free(struct task_struct *task)
 350 {
 351         WARN_ON(!plist_head_empty(&task->pi_waiters));
 352         WARN_ON(task->pi_blocked_on);
 353 }
 354
 355 /*
 356  * We fill out the fields in the waiter to store the information about
 357  * the deadlock. We print when we return. act_waiter can be NULL in
 358  * case of a remove waiter operation.
 359  */
 360 void debug_rt_mutex_deadlock(int detect, struct rt_mutex_waiter *act_waiter,
 361                              struct rt_mutex *lock)
 362 {
 363         struct task_struct *task;
 364
 365         if (!rt_trace_on || detect || !act_waiter)
 366                 return;
 367
 368         task = rt_mutex_owner(act_waiter->lock);
 369         if (task && task != current) {
 370                 act_waiter->deadlock_task_pid = task->pid;
 371                 act_waiter->deadlock_lock = lock;
 372         }
 373 }
 374
 375 void debug_rt_mutex_print_deadlock(struct rt_mutex_waiter *waiter)
 376 {
 377         struct task_struct *task;
 378
 379         if (!waiter->deadlock_lock || !rt_trace_on)
 380                 return;
 381
 382         task = find_task_by_pid(waiter->deadlock_task_pid);
 383         if (!task)
 384                 return;
 385
 386         TRACE_OFF_NOLOCK();
 387
 388         printk("\n============================================\n");
 389         printk(  "[ BUG: circular locking deadlock detected! ]\n");
 390         printk(  "--------------------------------------------\n");
 391         printk("%s/%d is deadlocking current task %s/%d\n\n",
 392                task->comm, task->pid, current->comm, current->pid);
 393
 394         printk("\n1) %s/%d is trying to acquire this lock:\n",
 395                current->comm, current->pid);
 396         printk_lock(waiter->lock, 1);
 397
 398         printk("... trying at:                 ");
 399         print_symbol("%s\n", waiter->ip);
 400
 401         printk("\n2) %s/%d is blocked on this lock:\n", task->comm, task->pid);
 402         printk_lock(waiter->deadlock_lock, 1);
 403
 404         rt_mutex_show_held_locks(current, 1);
 405         rt_mutex_show_held_locks(task, 1);
 406
 407         printk("\n%s/%d's [blocked] stackdump:\n\n", task->comm, task->pid);
 408         show_stack(task, NULL);
 409         printk("\n%s/%d's [current] stackdump:\n\n",
 410                current->comm, current->pid);
 411         dump_stack();
 412         rt_mutex_show_all_locks();
 413         printk("[ turning off deadlock detection."
 414                "Please report this trace. ]\n\n");
 415         local_irq_disable();
 416 }
 417
 418 void debug_rt_mutex_lock(struct rt_mutex *lock __IP_DECL__)
 419 {
 420         unsigned long flags;
 421
 422         if (rt_trace_on) {
 423                 TRACE_WARN_ON_LOCKED(!list_empty(&lock->held_list_entry));
 424
 425                 spin_lock_irqsave(&current->held_list_lock, flags);
 426                 list_add_tail(&lock->held_list_entry, &current->held_list_head);
 427                 spin_unlock_irqrestore(&current->held_list_lock, flags);
 428
 429                 lock->acquire_ip = ip;
 430         }
 431 }
 432
 433 void debug_rt_mutex_unlock(struct rt_mutex *lock)
 434 {
 435         unsigned long flags;
 436
 437         if (rt_trace_on) {
 438                 TRACE_WARN_ON_LOCKED(rt_mutex_owner(lock) != current);
 439                 TRACE_WARN_ON_LOCKED(list_empty(&lock->held_list_entry));
 440
 441                 spin_lock_irqsave(&current->held_list_lock, flags);
 442                 list_del_init(&lock->held_list_entry);
 443                 spin_unlock_irqrestore(&current->held_list_lock, flags);
 444         }
 445 }
 446
 447 void debug_rt_mutex_proxy_lock(struct rt_mutex *lock,
 448                                struct task_struct *powner __IP_DECL__)
 449 {
 450         unsigned long flags;
 451
 452         if (rt_trace_on) {
 453                 TRACE_WARN_ON_LOCKED(!list_empty(&lock->held_list_entry));
 454
 455                 spin_lock_irqsave(&powner->held_list_lock, flags);
 456                 list_add_tail(&lock->held_list_entry, &powner->held_list_head);
 457                 spin_unlock_irqrestore(&powner->held_list_lock, flags);
 458
 459                 lock->acquire_ip = ip;
 460         }
 461 }
 462
 463 void debug_rt_mutex_proxy_unlock(struct rt_mutex *lock)
 464 {
 465         unsigned long flags;
 466
 467         if (rt_trace_on) {
 468                 struct task_struct *owner = rt_mutex_owner(lock);
 469
 470                 TRACE_WARN_ON_LOCKED(!owner);
 471                 TRACE_WARN_ON_LOCKED(list_empty(&lock->held_list_entry));
 472
 473                 spin_lock_irqsave(&owner->held_list_lock, flags);
 474                 list_del_init(&lock->held_list_entry);
 475                 spin_unlock_irqrestore(&owner->held_list_lock, flags);
 476         }
 477 }
 478
 479 void debug_rt_mutex_init_waiter(struct rt_mutex_waiter *waiter)
 480 {
 481         memset(waiter, 0x11, sizeof(*waiter));
 482         plist_node_init(&waiter->list_entry, MAX_PRIO);
 483         plist_node_init(&waiter->pi_list_entry, MAX_PRIO);
 484 }
 485
 486 void debug_rt_mutex_free_waiter(struct rt_mutex_waiter *waiter)
 487 {
 488         TRACE_WARN_ON(!plist_node_empty(&waiter->list_entry));
 489         TRACE_WARN_ON(!plist_node_empty(&waiter->pi_list_entry));
 490         TRACE_WARN_ON(waiter->task);
 491         memset(waiter, 0x22, sizeof(*waiter));
 492 }
 493
 494 void debug_rt_mutex_init(struct rt_mutex *lock, const char *name)
 495 {
 496         void *addr = lock;
 497
 498         if (rt_trace_on) {
 499                 rt_mutex_debug_check_no_locks_freed(addr,
 500                                                     sizeof(struct rt_mutex));
 501                 INIT_LIST_HEAD(&lock->held_list_entry);
 502                 lock->name = name;
 503         }
 504 }
 505
 506 void rt_mutex_deadlock_account_lock(struct rt_mutex *lock, task_t *task)
 507 {
 508 }
 509
 510 void rt_mutex_deadlock_account_unlock(struct task_struct *task)
 511 {
 512 }
 513