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/rt_lock.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 #include <linux/debug_locks.h>
  30
  31 #include "rtmutex_common.h"
  32
  33 static void printk_task(struct task_struct *p)
  34 {
  35         if (p)
  36                 printk("%16s:%5d [%p, %3d]", p->comm, task_pid_nr(p), p, p->prio);
  37         else
  38                 printk("<none>");
  39 }
  40
  41 static void printk_lock(struct rt_mutex *lock, int print_owner)
  42 {
  43         if (lock->name)
  44                 printk(" [%p] {%s}\n",
  45                         lock, lock->name);
  46         else
  47                 printk(" [%p] {%s:%d}\n",
  48                         lock, lock->file, lock->line);
  49
  50         if (print_owner && rt_mutex_owner(lock)) {
  51                 printk(".. ->owner: %p\n", lock->owner);
  52                 printk(".. held by:  ");
  53                 printk_task(rt_mutex_owner(lock));
  54                 printk("\n");
  55         }
  56 }
  57
  58 void rt_mutex_debug_task_free(struct task_struct *task)
  59 {
  60         DEBUG_LOCKS_WARN_ON(!plist_head_empty(&task->pi_waiters));
  61         DEBUG_LOCKS_WARN_ON(task->pi_blocked_on);
  62 }
  63
  64 /*
  65  * We fill out the fields in the waiter to store the information about
  66  * the deadlock. We print when we return. act_waiter can be NULL in
  67  * case of a remove waiter operation.
  68  */
  69 void debug_rt_mutex_deadlock(int detect, struct rt_mutex_waiter *act_waiter,
  70                              struct rt_mutex *lock)
  71 {
  72         struct task_struct *task;
  73
  74         if (!debug_locks || detect || !act_waiter)
  75                 return;
  76
  77         task = rt_mutex_owner(act_waiter->lock);
  78         if (task && task != current) {
  79                 act_waiter->deadlock_task_pid = get_pid(task_pid(task));
  80                 act_waiter->deadlock_lock = lock;
  81         }
  82 }
  83
  84 void debug_rt_mutex_print_deadlock(struct rt_mutex_waiter *waiter)
  85 {
  86         struct task_struct *task;
  87
  88         if (!waiter->deadlock_lock || !debug_locks)
  89                 return;
  90
  91         rcu_read_lock();
  92         task = pid_task(waiter->deadlock_task_pid, PIDTYPE_PID);
  93         if (!task) {
  94                 rcu_read_unlock();
  95                 return;
  96         }
  97
  98         if (!debug_locks_off())
  99                 return;
 100
 101         printk("\n============================================\n");
 102         printk(  "[ BUG: circular locking deadlock detected! ]\n");
 103         printk(  "--------------------------------------------\n");
 104         printk("%s/%d is deadlocking current task %s/%d\n\n",
 105                task->comm, task_pid_nr(task),
 106                current->comm, task_pid_nr(current));
 107
 108         printk("\n1) %s/%d is trying to acquire this lock:\n",
 109                current->comm, task_pid_nr(current));
 110         printk_lock(waiter->lock, 1);
 111
 112         printk("\n2) %s/%d is blocked on this lock:\n",
 113                 task->comm, task_pid_nr(task));
 114         printk_lock(waiter->deadlock_lock, 1);
 115
 116         debug_show_held_locks(current);
 117         debug_show_held_locks(task);
 118
 119         printk("\n%s/%d's [blocked] stackdump:\n\n",
 120                 task->comm, task_pid_nr(task));
 121         show_stack(task, NULL);
 122         printk("\n%s/%d's [current] stackdump:\n\n",
 123                 current->comm, task_pid_nr(current));
 124         dump_stack();
 125         debug_show_all_locks();
 126         rcu_read_unlock();
 127
 128         printk("[ turning off deadlock detection."
 129                "Please report this trace. ]\n\n");
 130 }
 131
 132 void debug_rt_mutex_lock(struct rt_mutex *lock)
 133 {
 134 }
 135
 136 void debug_rt_mutex_unlock(struct rt_mutex *lock)
 137 {
 138         if (debug_locks)
 139                 DEBUG_LOCKS_WARN_ON(rt_mutex_owner(lock) != current);
 140 }
 141
 142 void
 143 debug_rt_mutex_proxy_lock(struct rt_mutex *lock, struct task_struct *powner)
 144 {
 145 }
 146
 147 void debug_rt_mutex_proxy_unlock(struct rt_mutex *lock)
 148 {
 149         DEBUG_LOCKS_WARN_ON(!rt_mutex_owner(lock));
 150 }
 151
 152 void debug_rt_mutex_init_waiter(struct rt_mutex_waiter *waiter)
 153 {
 154         memset(waiter, 0x11, sizeof(*waiter));
 155         plist_node_init(&waiter->list_entry, MAX_PRIO);
 156         plist_node_init(&waiter->pi_list_entry, MAX_PRIO);
 157         waiter->deadlock_task_pid = NULL;
 158 }
 159
 160 void debug_rt_mutex_free_waiter(struct rt_mutex_waiter *waiter)
 161 {
 162         put_pid(waiter->deadlock_task_pid);
 163         DEBUG_LOCKS_WARN_ON(!plist_node_empty(&waiter->list_entry));
 164         DEBUG_LOCKS_WARN_ON(!plist_node_empty(&waiter->pi_list_entry));
 165         DEBUG_LOCKS_WARN_ON(waiter->task);
 166         memset(waiter, 0x22, sizeof(*waiter));
 167 }
 168
 169 void debug_rt_mutex_init(struct rt_mutex *lock, const char *name)
 170 {
 171         /*
 172          * Make sure we are not reinitializing a held lock:
 173          */
 174         debug_check_no_locks_freed((void *)lock, sizeof(*lock));
 175         lock->name = name;
 176 }
 177
 178 void
 179 rt_mutex_deadlock_account_lock(struct rt_mutex *lock, struct task_struct *task)
 180 {
 181 #ifdef CONFIG_DEBUG_PREEMPT
 182         if (atomic_read(&task->lock_count) >= MAX_LOCK_STACK) {
 183                 if (!debug_locks_off())
 184                         return;
 185                 printk("BUG: %s/%d: lock count overflow!\n",
 186                         task->comm, task->pid);
 187                 dump_stack();
 188                 return;
 189         }
 190 #ifdef CONFIG_PREEMPT_RT
 191         task->owned_lock[atomic_read(&task->lock_count)] = lock;
 192 #endif
 193         atomic_inc(&task->lock_count);
 194 #endif
 195 }
 196
 197 void rt_mutex_deadlock_account_unlock(struct task_struct *task)
 198 {
 199 #ifdef CONFIG_DEBUG_PREEMPT
 200         if (!atomic_read(&task->lock_count)) {
 201                 if (!debug_locks_off())
 202                         return;
 203                 printk("BUG: %s/%d: lock count underflow!\n",
 204                         task->comm, task->pid);
 205                 dump_stack();
 206                 return;
 207         }
 208         atomic_dec(&task->lock_count);
 209 #ifdef CONFIG_PREEMPT_RT
 210         task->owned_lock[atomic_read(&task->lock_count)] = NULL;
 211 #endif
 212 #endif
 213 }