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/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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