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() \
36 do { \
37 if (rt_trace_on) { \
38 rt_trace_on = 0; \
39 console_verbose(); \
40 if (spin_is_locked(¤t->pi_lock)) \
41 spin_unlock(¤t->pi_lock); \
42 } \
43 } while (0)
44
45 # define TRACE_OFF_NOLOCK() \
46 do { \
47 if (rt_trace_on) { \
48 rt_trace_on = 0; \
49 console_verbose(); \
50 } \
51 } while (0)
52
53 # define TRACE_BUG_LOCKED() \
54 do { \
55 TRACE_OFF(); \
56 BUG(); \
57 } while (0)
58
59 # define TRACE_WARN_ON_LOCKED(c) \
60 do { \
61 if (unlikely(c)) { \
62 TRACE_OFF(); \
63 WARN_ON(1); \
64 } \
65 } while (0)
66
67 # define TRACE_BUG_ON_LOCKED(c) \
68 do { \
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 */
85 static int rt_trace_on = 1;
86
87 static 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
95 static 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
112 void 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 */
123 void 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
138 void 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
186 void debug_rt_mutex_lock(struct rt_mutex *lock)
187 {
188 }
189
190 void debug_rt_mutex_unlock(struct rt_mutex *lock)
191 {
192 TRACE_WARN_ON_LOCKED(rt_mutex_owner(lock) != current);
193 }
194
195 void
196 debug_rt_mutex_proxy_lock(struct rt_mutex *lock, struct task_struct *powner)
197 {
198 }
199
200 void debug_rt_mutex_proxy_unlock(struct rt_mutex *lock)
201 {
202 TRACE_WARN_ON_LOCKED(!rt_mutex_owner(lock));
203 }
204
205 void 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
213 void 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 TRACE_WARN_ON(waiter->task);
219 memset(waiter, 0x22, sizeof(*waiter));
220 }
221
222 void debug_rt_mutex_init(struct rt_mutex *lock, const char *name)
223 {
224 /*
225 * Make sure we are not reinitializing a held lock:
226 */
227 debug_check_no_locks_freed((void *)lock, sizeof(*lock));
228 lock->name = name;
229 }
230
231 void
232 rt_mutex_deadlock_account_lock(struct rt_mutex *lock, struct task_struct *task)
233 {
234 }
235
236 void rt_mutex_deadlock_account_unlock(struct task_struct *task)
237 {
238 }
239
240
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