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
printk_task(struct task_struct * p)32 static 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
printk_lock(struct rt_mutex * lock,int print_owner)40 static 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
rt_mutex_debug_task_free(struct task_struct * task)57 void 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 */
debug_rt_mutex_deadlock(int detect,struct rt_mutex_waiter * act_waiter,struct rt_mutex * lock)68 void 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
debug_rt_mutex_print_deadlock(struct rt_mutex_waiter * waiter)83 void 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
debug_rt_mutex_lock(struct rt_mutex * lock)134 void debug_rt_mutex_lock(struct rt_mutex *lock)
135 {
136 }
137
debug_rt_mutex_unlock(struct rt_mutex * lock)138 void debug_rt_mutex_unlock(struct rt_mutex *lock)
139 {
140 DEBUG_LOCKS_WARN_ON(rt_mutex_owner(lock) != current);
141 }
142
143 void
debug_rt_mutex_proxy_lock(struct rt_mutex * lock,struct task_struct * powner)144 debug_rt_mutex_proxy_lock(struct rt_mutex *lock, struct task_struct *powner)
145 {
146 }
147
debug_rt_mutex_proxy_unlock(struct rt_mutex * lock)148 void debug_rt_mutex_proxy_unlock(struct rt_mutex *lock)
149 {
150 DEBUG_LOCKS_WARN_ON(!rt_mutex_owner(lock));
151 }
152
debug_rt_mutex_init_waiter(struct rt_mutex_waiter * waiter)153 void 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
debug_rt_mutex_free_waiter(struct rt_mutex_waiter * waiter)161 void 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
debug_rt_mutex_init(struct rt_mutex * lock,const char * name)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 void
rt_mutex_deadlock_account_lock(struct rt_mutex * lock,struct task_struct * task)179 rt_mutex_deadlock_account_lock(struct rt_mutex *lock, struct task_struct *task)
180 {
181 }
182
rt_mutex_deadlock_account_unlock(struct task_struct * task)183 void rt_mutex_deadlock_account_unlock(struct task_struct *task)
184 {
185 }
186
187