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/sched/debug.h>
22 #include <linux/delay.h>
23 #include <linux/export.h>
24 #include <linux/spinlock.h>
25 #include <linux/kallsyms.h>
26 #include <linux/syscalls.h>
27 #include <linux/interrupt.h>
28 #include <linux/rbtree.h>
29 #include <linux/fs.h>
30 #include <linux/debug_locks.h>
31
32 #include "rtmutex_common.h"
33
34 static void printk_task(struct task_struct *p)
35 {
36 if (p)
37 printk("%16s:%5d [%p, %3d]", p->comm, task_pid_nr(p), p, p->prio);
38 else
39 printk("<none>");
40 }
41
42 static void printk_lock(struct rt_mutex *lock, int print_owner)
43 {
44 if (lock->name)
45 printk(" [%p] {%s}\n",
46 lock, lock->name);
47 else
48 printk(" [%p] {%s:%d}\n",
49 lock, lock->file, lock->line);
50
51 if (print_owner && rt_mutex_owner(lock)) {
52 printk(".. ->owner: %p\n", lock->owner);
53 printk(".. held by: ");
54 printk_task(rt_mutex_owner(lock));
55 printk("\n");
56 }
57 }
58
59 void rt_mutex_debug_task_free(struct task_struct *task)
60 {
61 DEBUG_LOCKS_WARN_ON(!RB_EMPTY_ROOT(&task->pi_waiters));
62 DEBUG_LOCKS_WARN_ON(task->pi_blocked_on);
63 }
64
65 /*
66 * We fill out the fields in the waiter to store the information about
67 * the deadlock. We print when we return. act_waiter can be NULL in
68 * case of a remove waiter operation.
69 */
70 void debug_rt_mutex_deadlock(enum rtmutex_chainwalk chwalk,
71 struct rt_mutex_waiter *act_waiter,
72 struct rt_mutex *lock)
73 {
74 struct task_struct *task;
75
76 if (!debug_locks || chwalk == RT_MUTEX_FULL_CHAINWALK || !act_waiter)
77 return;
78
79 task = rt_mutex_owner(act_waiter->lock);
80 if (task && task != current) {
81 act_waiter->deadlock_task_pid = get_pid(task_pid(task));
82 act_waiter->deadlock_lock = lock;
83 }
84 }
85
86 void debug_rt_mutex_print_deadlock(struct rt_mutex_waiter *waiter)
87 {
88 struct task_struct *task;
89
90 if (!waiter->deadlock_lock || !debug_locks)
91 return;
92
93 rcu_read_lock();
94 task = pid_task(waiter->deadlock_task_pid, PIDTYPE_PID);
95 if (!task) {
96 rcu_read_unlock();
97 return;
98 }
99
100 if (!debug_locks_off()) {
101 rcu_read_unlock();
102 return;
103 }
104
105 pr_warn("\n");
106 pr_warn("============================================\n");
107 pr_warn("WARNING: circular locking deadlock detected!\n");
108 pr_warn("%s\n", print_tainted());
109 pr_warn("--------------------------------------------\n");
110 printk("%s/%d is deadlocking current task %s/%d\n\n",
111 task->comm, task_pid_nr(task),
112 current->comm, task_pid_nr(current));
113
114 printk("\n1) %s/%d is trying to acquire this lock:\n",
115 current->comm, task_pid_nr(current));
116 printk_lock(waiter->lock, 1);
117
118 printk("\n2) %s/%d is blocked on this lock:\n",
119 task->comm, task_pid_nr(task));
120 printk_lock(waiter->deadlock_lock, 1);
121
122 debug_show_held_locks(current);
123 debug_show_held_locks(task);
124
125 printk("\n%s/%d's [blocked] stackdump:\n\n",
126 task->comm, task_pid_nr(task));
127 show_stack(task, NULL);
128 printk("\n%s/%d's [current] stackdump:\n\n",
129 current->comm, task_pid_nr(current));
130 dump_stack();
131 debug_show_all_locks();
132 rcu_read_unlock();
133
134 printk("[ turning off deadlock detection."
135 "Please report this trace. ]\n\n");
136 }
137
138 void debug_rt_mutex_lock(struct rt_mutex *lock)
139 {
140 }
141
142 void debug_rt_mutex_unlock(struct rt_mutex *lock)
143 {
144 DEBUG_LOCKS_WARN_ON(rt_mutex_owner(lock) != current);
145 }
146
147 void
148 debug_rt_mutex_proxy_lock(struct rt_mutex *lock, struct task_struct *powner)
149 {
150 }
151
152 void debug_rt_mutex_proxy_unlock(struct rt_mutex *lock)
153 {
154 DEBUG_LOCKS_WARN_ON(!rt_mutex_owner(lock));
155 }
156
157 void debug_rt_mutex_init_waiter(struct rt_mutex_waiter *waiter)
158 {
159 memset(waiter, 0x11, sizeof(*waiter));
160 waiter->deadlock_task_pid = NULL;
161 }
162
163 void debug_rt_mutex_free_waiter(struct rt_mutex_waiter *waiter)
164 {
165 put_pid(waiter->deadlock_task_pid);
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
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