Root/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/sched.h>
20#include <linux/delay.h>
21#include <linux/export.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
32static void printk_task(struct task_struct *p)
33{
34    if (p)
35        printk("%16s:%5d [%p, %3d]", p->comm, task_pid_nr(p), p, p->prio);
36    else
37        printk("<none>");
38}
39
40static void printk_lock(struct rt_mutex *lock, int print_owner)
41{
42    if (lock->name)
43        printk(" [%p] {%s}\n",
44            lock, lock->name);
45    else
46        printk(" [%p] {%s:%d}\n",
47            lock, lock->file, lock->line);
48
49    if (print_owner && rt_mutex_owner(lock)) {
50        printk(".. ->owner: %p\n", lock->owner);
51        printk(".. held by: ");
52        printk_task(rt_mutex_owner(lock));
53        printk("\n");
54    }
55}
56
57void rt_mutex_debug_task_free(struct task_struct *task)
58{
59    DEBUG_LOCKS_WARN_ON(!plist_head_empty(&task->pi_waiters));
60    DEBUG_LOCKS_WARN_ON(task->pi_blocked_on);
61}
62
63/*
64 * We fill out the fields in the waiter to store the information about
65 * the deadlock. We print when we return. act_waiter can be NULL in
66 * case of a remove waiter operation.
67 */
68void debug_rt_mutex_deadlock(int detect, struct rt_mutex_waiter *act_waiter,
69                 struct rt_mutex *lock)
70{
71    struct task_struct *task;
72
73    if (!debug_locks || detect || !act_waiter)
74        return;
75
76    task = rt_mutex_owner(act_waiter->lock);
77    if (task && task != current) {
78        act_waiter->deadlock_task_pid = get_pid(task_pid(task));
79        act_waiter->deadlock_lock = lock;
80    }
81}
82
83void debug_rt_mutex_print_deadlock(struct rt_mutex_waiter *waiter)
84{
85    struct task_struct *task;
86
87    if (!waiter->deadlock_lock || !debug_locks)
88        return;
89
90    rcu_read_lock();
91    task = pid_task(waiter->deadlock_task_pid, PIDTYPE_PID);
92    if (!task) {
93        rcu_read_unlock();
94        return;
95    }
96
97    if (!debug_locks_off()) {
98        rcu_read_unlock();
99        return;
100    }
101
102    printk("\n============================================\n");
103    printk( "[ BUG: circular locking deadlock detected! ]\n");
104    printk("%s\n", print_tainted());
105    printk( "--------------------------------------------\n");
106    printk("%s/%d is deadlocking current task %s/%d\n\n",
107           task->comm, task_pid_nr(task),
108           current->comm, task_pid_nr(current));
109
110    printk("\n1) %s/%d is trying to acquire this lock:\n",
111           current->comm, task_pid_nr(current));
112    printk_lock(waiter->lock, 1);
113
114    printk("\n2) %s/%d is blocked on this lock:\n",
115        task->comm, task_pid_nr(task));
116    printk_lock(waiter->deadlock_lock, 1);
117
118    debug_show_held_locks(current);
119    debug_show_held_locks(task);
120
121    printk("\n%s/%d's [blocked] stackdump:\n\n",
122        task->comm, task_pid_nr(task));
123    show_stack(task, NULL);
124    printk("\n%s/%d's [current] stackdump:\n\n",
125        current->comm, task_pid_nr(current));
126    dump_stack();
127    debug_show_all_locks();
128    rcu_read_unlock();
129
130    printk("[ turning off deadlock detection."
131           "Please report this trace. ]\n\n");
132}
133
134void debug_rt_mutex_lock(struct rt_mutex *lock)
135{
136}
137
138void debug_rt_mutex_unlock(struct rt_mutex *lock)
139{
140    DEBUG_LOCKS_WARN_ON(rt_mutex_owner(lock) != current);
141}
142
143void
144debug_rt_mutex_proxy_lock(struct rt_mutex *lock, struct task_struct *powner)
145{
146}
147
148void debug_rt_mutex_proxy_unlock(struct rt_mutex *lock)
149{
150    DEBUG_LOCKS_WARN_ON(!rt_mutex_owner(lock));
151}
152
153void debug_rt_mutex_init_waiter(struct rt_mutex_waiter *waiter)
154{
155    memset(waiter, 0x11, sizeof(*waiter));
156    plist_node_init(&waiter->list_entry, MAX_PRIO);
157    plist_node_init(&waiter->pi_list_entry, MAX_PRIO);
158    waiter->deadlock_task_pid = NULL;
159}
160
161void debug_rt_mutex_free_waiter(struct rt_mutex_waiter *waiter)
162{
163    put_pid(waiter->deadlock_task_pid);
164    DEBUG_LOCKS_WARN_ON(!plist_node_empty(&waiter->list_entry));
165    DEBUG_LOCKS_WARN_ON(!plist_node_empty(&waiter->pi_list_entry));
166    memset(waiter, 0x22, sizeof(*waiter));
167}
168
169void 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
178void
179rt_mutex_deadlock_account_lock(struct rt_mutex *lock, struct task_struct *task)
180{
181}
182
183void rt_mutex_deadlock_account_unlock(struct task_struct *task)
184{
185}
186
187

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