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/rbtree.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(!RB_EMPTY_ROOT(&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(enum rtmutex_chainwalk chwalk,
70 struct rt_mutex_waiter *act_waiter,
71 struct rt_mutex *lock)
72 {
73 struct task_struct *task;
74
75 if (!debug_locks || chwalk == RT_MUTEX_FULL_CHAINWALK || !act_waiter)
76 return;
77
78 task = rt_mutex_owner(act_waiter->lock);
79 if (task && task != current) {
80 act_waiter->deadlock_task_pid = get_pid(task_pid(task));
81 act_waiter->deadlock_lock = lock;
82 }
83 }
84
85 void debug_rt_mutex_print_deadlock(struct rt_mutex_waiter *waiter)
86 {
87 struct task_struct *task;
88
89 if (!waiter->deadlock_lock || !debug_locks)
90 return;
91
92 rcu_read_lock();
93 task = pid_task(waiter->deadlock_task_pid, PIDTYPE_PID);
94 if (!task) {
95 rcu_read_unlock();
96 return;
97 }
98
99 if (!debug_locks_off()) {
100 rcu_read_unlock();
101 return;
102 }
103
104 printk("\n============================================\n");
105 printk( "[ BUG: circular locking deadlock detected! ]\n");
106 printk("%s\n", print_tainted());
107 printk( "--------------------------------------------\n");
108 printk("%s/%d is deadlocking current task %s/%d\n\n",
109 task->comm, task_pid_nr(task),
110 current->comm, task_pid_nr(current));
111
112 printk("\n1) %s/%d is trying to acquire this lock:\n",
113 current->comm, task_pid_nr(current));
114 printk_lock(waiter->lock, 1);
115
116 printk("\n2) %s/%d is blocked on this lock:\n",
117 task->comm, task_pid_nr(task));
118 printk_lock(waiter->deadlock_lock, 1);
119
120 debug_show_held_locks(current);
121 debug_show_held_locks(task);
122
123 printk("\n%s/%d's [blocked] stackdump:\n\n",
124 task->comm, task_pid_nr(task));
125 show_stack(task, NULL);
126 printk("\n%s/%d's [current] stackdump:\n\n",
127 current->comm, task_pid_nr(current));
128 dump_stack();
129 debug_show_all_locks();
130 rcu_read_unlock();
131
132 printk("[ turning off deadlock detection."
133 "Please report this trace. ]\n\n");
134 }
135
136 void debug_rt_mutex_lock(struct rt_mutex *lock)
137 {
138 }
139
140 void debug_rt_mutex_unlock(struct rt_mutex *lock)
141 {
142 DEBUG_LOCKS_WARN_ON(rt_mutex_owner(lock) != current);
143 }
144
145 void
146 debug_rt_mutex_proxy_lock(struct rt_mutex *lock, struct task_struct *powner)
147 {
148 }
149
150 void debug_rt_mutex_proxy_unlock(struct rt_mutex *lock)
151 {
152 DEBUG_LOCKS_WARN_ON(!rt_mutex_owner(lock));
153 }
154
155 void debug_rt_mutex_init_waiter(struct rt_mutex_waiter *waiter)
156 {
157 memset(waiter, 0x11, sizeof(*waiter));
158 waiter->deadlock_task_pid = NULL;
159 }
160
161 void debug_rt_mutex_free_waiter(struct rt_mutex_waiter *waiter)
162 {
163 put_pid(waiter->deadlock_task_pid);
164 memset(waiter, 0x22, sizeof(*waiter));
165 }
166
167 void debug_rt_mutex_init(struct rt_mutex *lock, const char *name)
168 {
169 /*
170 * Make sure we are not reinitializing a held lock:
171 */
172 debug_check_no_locks_freed((void *)lock, sizeof(*lock));
173 lock->name = name;
174 }
175
176
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