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/sched/rt.h>
  21#include <linux/delay.h>
  22#include <linux/export.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
  33static 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
  41static 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
  58void 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 */
  69void 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
  84void 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                rcu_read_unlock();
 100                return;
 101        }
 102
 103        printk("\n============================================\n");
 104        printk(  "[ BUG: circular locking deadlock detected! ]\n");
 105        printk("%s\n", print_tainted());
 106        printk(  "--------------------------------------------\n");
 107        printk("%s/%d is deadlocking current task %s/%d\n\n",
 108               task->comm, task_pid_nr(task),
 109               current->comm, task_pid_nr(current));
 110
 111        printk("\n1) %s/%d is trying to acquire this lock:\n",
 112               current->comm, task_pid_nr(current));
 113        printk_lock(waiter->lock, 1);
 114
 115        printk("\n2) %s/%d is blocked on this lock:\n",
 116                task->comm, task_pid_nr(task));
 117        printk_lock(waiter->deadlock_lock, 1);
 118
 119        debug_show_held_locks(current);
 120        debug_show_held_locks(task);
 121
 122        printk("\n%s/%d's [blocked] stackdump:\n\n",
 123                task->comm, task_pid_nr(task));
 124        show_stack(task, NULL);
 125        printk("\n%s/%d's [current] stackdump:\n\n",
 126                current->comm, task_pid_nr(current));
 127        dump_stack();
 128        debug_show_all_locks();
 129        rcu_read_unlock();
 130
 131        printk("[ turning off deadlock detection."
 132               "Please report this trace. ]\n\n");
 133}
 134
 135void debug_rt_mutex_lock(struct rt_mutex *lock)
 136{
 137}
 138
 139void debug_rt_mutex_unlock(struct rt_mutex *lock)
 140{
 141        DEBUG_LOCKS_WARN_ON(rt_mutex_owner(lock) != current);
 142}
 143
 144void
 145debug_rt_mutex_proxy_lock(struct rt_mutex *lock, struct task_struct *powner)
 146{
 147}
 148
 149void debug_rt_mutex_proxy_unlock(struct rt_mutex *lock)
 150{
 151        DEBUG_LOCKS_WARN_ON(!rt_mutex_owner(lock));
 152}
 153
 154void debug_rt_mutex_init_waiter(struct rt_mutex_waiter *waiter)
 155{
 156        memset(waiter, 0x11, sizeof(*waiter));
 157        plist_node_init(&waiter->list_entry, MAX_PRIO);
 158        plist_node_init(&waiter->pi_list_entry, MAX_PRIO);
 159        waiter->deadlock_task_pid = NULL;
 160}
 161
 162void debug_rt_mutex_free_waiter(struct rt_mutex_waiter *waiter)
 163{
 164        put_pid(waiter->deadlock_task_pid);
 165        DEBUG_LOCKS_WARN_ON(!plist_node_empty(&waiter->list_entry));
 166        DEBUG_LOCKS_WARN_ON(!plist_node_empty(&waiter->pi_list_entry));
 167        memset(waiter, 0x22, sizeof(*waiter));
 168}
 169
 170void debug_rt_mutex_init(struct rt_mutex *lock, const char *name)
 171{
 172        /*
 173         * Make sure we are not reinitializing a held lock:
 174         */
 175        debug_check_no_locks_freed((void *)lock, sizeof(*lock));
 176        lock->name = name;
 177}
 178
 179void
 180rt_mutex_deadlock_account_lock(struct rt_mutex *lock, struct task_struct *task)
 181{
 182}
 183
 184void rt_mutex_deadlock_account_unlock(struct task_struct *task)
 185{
 186}
 187
 188
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