linux/kernel/rtmutex-debug.c
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   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/sched.h>
  20#include <linux/delay.h>
  21#include <linux/module.h>
  22#include <linux/spinlock.h>
  23#include <linux/kallsyms.h>
  24#include <linux/syscalls.h>
  25#include <linux/interrupt.h>
  26#include <linux/plist.h>
  27#include <linux/fs.h>
  28#include <linux/debug_locks.h>
  29
  30#include "rtmutex_common.h"
  31
  32# define TRACE_WARN_ON(x)                       WARN_ON(x)
  33# define TRACE_BUG_ON(x)                        BUG_ON(x)
  34
  35# define TRACE_OFF()                                            \
  36do {                                                            \
  37        if (rt_trace_on) {                                      \
  38                rt_trace_on = 0;                                \
  39                console_verbose();                              \
  40                if (raw_spin_is_locked(&current->pi_lock))      \
  41                        raw_spin_unlock(&current->pi_lock);     \
  42        }                                                       \
  43} while (0)
  44
  45# define TRACE_OFF_NOLOCK()                                     \
  46do {                                                            \
  47        if (rt_trace_on) {                                      \
  48                rt_trace_on = 0;                                \
  49                console_verbose();                              \
  50        }                                                       \
  51} while (0)
  52
  53# define TRACE_BUG_LOCKED()                     \
  54do {                                            \
  55        TRACE_OFF();                            \
  56        BUG();                                  \
  57} while (0)
  58
  59# define TRACE_WARN_ON_LOCKED(c)                \
  60do {                                            \
  61        if (unlikely(c)) {                      \
  62                TRACE_OFF();                    \
  63                WARN_ON(1);                     \
  64        }                                       \
  65} while (0)
  66
  67# define TRACE_BUG_ON_LOCKED(c)                 \
  68do {                                            \
  69        if (unlikely(c))                        \
  70                TRACE_BUG_LOCKED();             \
  71} while (0)
  72
  73#ifdef CONFIG_SMP
  74# define SMP_TRACE_BUG_ON_LOCKED(c)     TRACE_BUG_ON_LOCKED(c)
  75#else
  76# define SMP_TRACE_BUG_ON_LOCKED(c)     do { } while (0)
  77#endif
  78
  79/*
  80 * deadlock detection flag. We turn it off when we detect
  81 * the first problem because we dont want to recurse back
  82 * into the tracing code when doing error printk or
  83 * executing a BUG():
  84 */
  85static int rt_trace_on = 1;
  86
  87static void printk_task(struct task_struct *p)
  88{
  89        if (p)
  90                printk("%16s:%5d [%p, %3d]", p->comm, task_pid_nr(p), p, p->prio);
  91        else
  92                printk("<none>");
  93}
  94
  95static void printk_lock(struct rt_mutex *lock, int print_owner)
  96{
  97        if (lock->name)
  98                printk(" [%p] {%s}\n",
  99                        lock, lock->name);
 100        else
 101                printk(" [%p] {%s:%d}\n",
 102                        lock, lock->file, lock->line);
 103
 104        if (print_owner && rt_mutex_owner(lock)) {
 105                printk(".. ->owner: %p\n", lock->owner);
 106                printk(".. held by:  ");
 107                printk_task(rt_mutex_owner(lock));
 108                printk("\n");
 109        }
 110}
 111
 112void rt_mutex_debug_task_free(struct task_struct *task)
 113{
 114        WARN_ON(!plist_head_empty(&task->pi_waiters));
 115        WARN_ON(task->pi_blocked_on);
 116}
 117
 118/*
 119 * We fill out the fields in the waiter to store the information about
 120 * the deadlock. We print when we return. act_waiter can be NULL in
 121 * case of a remove waiter operation.
 122 */
 123void debug_rt_mutex_deadlock(int detect, struct rt_mutex_waiter *act_waiter,
 124                             struct rt_mutex *lock)
 125{
 126        struct task_struct *task;
 127
 128        if (!rt_trace_on || detect || !act_waiter)
 129                return;
 130
 131        task = rt_mutex_owner(act_waiter->lock);
 132        if (task && task != current) {
 133                act_waiter->deadlock_task_pid = get_pid(task_pid(task));
 134                act_waiter->deadlock_lock = lock;
 135        }
 136}
 137
 138void debug_rt_mutex_print_deadlock(struct rt_mutex_waiter *waiter)
 139{
 140        struct task_struct *task;
 141
 142        if (!waiter->deadlock_lock || !rt_trace_on)
 143                return;
 144
 145        rcu_read_lock();
 146        task = pid_task(waiter->deadlock_task_pid, PIDTYPE_PID);
 147        if (!task) {
 148                rcu_read_unlock();
 149                return;
 150        }
 151
 152        TRACE_OFF_NOLOCK();
 153
 154        printk("\n============================================\n");
 155        printk(  "[ BUG: circular locking deadlock detected! ]\n");
 156        printk(  "--------------------------------------------\n");
 157        printk("%s/%d is deadlocking current task %s/%d\n\n",
 158               task->comm, task_pid_nr(task),
 159               current->comm, task_pid_nr(current));
 160
 161        printk("\n1) %s/%d is trying to acquire this lock:\n",
 162               current->comm, task_pid_nr(current));
 163        printk_lock(waiter->lock, 1);
 164
 165        printk("\n2) %s/%d is blocked on this lock:\n",
 166                task->comm, task_pid_nr(task));
 167        printk_lock(waiter->deadlock_lock, 1);
 168
 169        debug_show_held_locks(current);
 170        debug_show_held_locks(task);
 171
 172        printk("\n%s/%d's [blocked] stackdump:\n\n",
 173                task->comm, task_pid_nr(task));
 174        show_stack(task, NULL);
 175        printk("\n%s/%d's [current] stackdump:\n\n",
 176                current->comm, task_pid_nr(current));
 177        dump_stack();
 178        debug_show_all_locks();
 179        rcu_read_unlock();
 180
 181        printk("[ turning off deadlock detection."
 182               "Please report this trace. ]\n\n");
 183        local_irq_disable();
 184}
 185
 186void debug_rt_mutex_lock(struct rt_mutex *lock)
 187{
 188}
 189
 190void debug_rt_mutex_unlock(struct rt_mutex *lock)
 191{
 192        TRACE_WARN_ON_LOCKED(rt_mutex_owner(lock) != current);
 193}
 194
 195void
 196debug_rt_mutex_proxy_lock(struct rt_mutex *lock, struct task_struct *powner)
 197{
 198}
 199
 200void debug_rt_mutex_proxy_unlock(struct rt_mutex *lock)
 201{
 202        TRACE_WARN_ON_LOCKED(!rt_mutex_owner(lock));
 203}
 204
 205void debug_rt_mutex_init_waiter(struct rt_mutex_waiter *waiter)
 206{
 207        memset(waiter, 0x11, sizeof(*waiter));
 208        plist_node_init(&waiter->list_entry, MAX_PRIO);
 209        plist_node_init(&waiter->pi_list_entry, MAX_PRIO);
 210        waiter->deadlock_task_pid = NULL;
 211}
 212
 213void debug_rt_mutex_free_waiter(struct rt_mutex_waiter *waiter)
 214{
 215        put_pid(waiter->deadlock_task_pid);
 216        TRACE_WARN_ON(!plist_node_empty(&waiter->list_entry));
 217        TRACE_WARN_ON(!plist_node_empty(&waiter->pi_list_entry));
 218        memset(waiter, 0x22, sizeof(*waiter));
 219}
 220
 221void debug_rt_mutex_init(struct rt_mutex *lock, const char *name)
 222{
 223        /*
 224         * Make sure we are not reinitializing a held lock:
 225         */
 226        debug_check_no_locks_freed((void *)lock, sizeof(*lock));
 227        lock->name = name;
 228}
 229
 230void
 231rt_mutex_deadlock_account_lock(struct rt_mutex *lock, struct task_struct *task)
 232{
 233}
 234
 235void rt_mutex_deadlock_account_unlock(struct task_struct *task)
 236{
 237}
 238
 239
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