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#ifdef CONFIG_DEBUG_RT_MUTEXES
33# include "rtmutex-debug.h"
34#else
35# include "rtmutex.h"
36#endif
37
38# define TRACE_WARN_ON(x)			WARN_ON(x)
39# define TRACE_BUG_ON(x)			BUG_ON(x)
40
41# define TRACE_OFF()						\
42do {								\
43	if (rt_trace_on) {					\
44		rt_trace_on = 0;				\
45		console_verbose();				\
46		if (spin_is_locked(&current->pi_lock))		\
47			spin_unlock(&current->pi_lock);		\
48	}							\
49} while (0)
50
51# define TRACE_OFF_NOLOCK()					\
52do {								\
53	if (rt_trace_on) {					\
54		rt_trace_on = 0;				\
55		console_verbose();				\
56	}							\
57} while (0)
58
59# define TRACE_BUG_LOCKED()			\
60do {						\
61	TRACE_OFF();				\
62	BUG();					\
63} while (0)
64
65# define TRACE_WARN_ON_LOCKED(c)		\
66do {						\
67	if (unlikely(c)) {			\
68		TRACE_OFF();			\
69		WARN_ON(1);			\
70	}					\
71} while (0)
72
73# define TRACE_BUG_ON_LOCKED(c)			\
74do {						\
75	if (unlikely(c))			\
76		TRACE_BUG_LOCKED();		\
77} while (0)
78
79#ifdef CONFIG_SMP
80# define SMP_TRACE_BUG_ON_LOCKED(c)	TRACE_BUG_ON_LOCKED(c)
81#else
82# define SMP_TRACE_BUG_ON_LOCKED(c)	do { } while (0)
83#endif
84
85/*
86 * deadlock detection flag. We turn it off when we detect
87 * the first problem because we dont want to recurse back
88 * into the tracing code when doing error printk or
89 * executing a BUG():
90 */
91int rt_trace_on = 1;
92
93void deadlock_trace_off(void)
94{
95	rt_trace_on = 0;
96}
97
98static void printk_task(struct task_struct *p)
99{
100	if (p)
101		printk("%16s:%5d [%p, %3d]", p->comm, p->pid, p, p->prio);
102	else
103		printk("<none>");
104}
105
106static void printk_lock(struct rt_mutex *lock, int print_owner)
107{
108	if (lock->name)
109		printk(" [%p] {%s}\n",
110			lock, lock->name);
111	else
112		printk(" [%p] {%s:%d}\n",
113			lock, lock->file, lock->line);
114
115	if (print_owner && rt_mutex_owner(lock)) {
116		printk(".. ->owner: %p\n", lock->owner);
117		printk(".. held by:  ");
118		printk_task(rt_mutex_owner(lock));
119		printk("\n");
120	}
121}
122
123void rt_mutex_debug_task_free(struct task_struct *task)
124{
125	WARN_ON(!plist_head_empty(&task->pi_waiters));
126	WARN_ON(task->pi_blocked_on);
127}
128
129/*
130 * We fill out the fields in the waiter to store the information about
131 * the deadlock. We print when we return. act_waiter can be NULL in
132 * case of a remove waiter operation.
133 */
134void debug_rt_mutex_deadlock(int detect, struct rt_mutex_waiter *act_waiter,
135			     struct rt_mutex *lock)
136{
137	struct task_struct *task;
138
139	if (!rt_trace_on || detect || !act_waiter)
140		return;
141
142	task = rt_mutex_owner(act_waiter->lock);
143	if (task && task != current) {
144		act_waiter->deadlock_task_pid = task->pid;
145		act_waiter->deadlock_lock = lock;
146	}
147}
148
149void debug_rt_mutex_print_deadlock(struct rt_mutex_waiter *waiter)
150{
151	struct task_struct *task;
152
153	if (!waiter->deadlock_lock || !rt_trace_on)
154		return;
155
156	task = find_task_by_pid(waiter->deadlock_task_pid);
157	if (!task)
158		return;
159
160	TRACE_OFF_NOLOCK();
161
162	printk("\n============================================\n");
163	printk(  "[ BUG: circular locking deadlock detected! ]\n");
164	printk(  "--------------------------------------------\n");
165	printk("%s/%d is deadlocking current task %s/%d\n\n",
166	       task->comm, task->pid, current->comm, current->pid);
167
168	printk("\n1) %s/%d is trying to acquire this lock:\n",
169	       current->comm, current->pid);
170	printk_lock(waiter->lock, 1);
171
172	printk("\n2) %s/%d is blocked on this lock:\n", task->comm, task->pid);
173	printk_lock(waiter->deadlock_lock, 1);
174
175	debug_show_held_locks(current);
176	debug_show_held_locks(task);
177
178	printk("\n%s/%d's [blocked] stackdump:\n\n", task->comm, task->pid);
179	show_stack(task, NULL);
180	printk("\n%s/%d's [current] stackdump:\n\n",
181	       current->comm, current->pid);
182	dump_stack();
183	debug_show_all_locks();
184
185	printk("[ turning off deadlock detection."
186	       "Please report this trace. ]\n\n");
187	local_irq_disable();
188}
189
190void debug_rt_mutex_lock(struct rt_mutex *lock)
191{
192}
193
194void debug_rt_mutex_unlock(struct rt_mutex *lock)
195{
196	TRACE_WARN_ON_LOCKED(rt_mutex_owner(lock) != current);
197}
198
199void
200debug_rt_mutex_proxy_lock(struct rt_mutex *lock, struct task_struct *powner)
201{
202}
203
204void debug_rt_mutex_proxy_unlock(struct rt_mutex *lock)
205{
206	TRACE_WARN_ON_LOCKED(!rt_mutex_owner(lock));
207}
208
209void debug_rt_mutex_init_waiter(struct rt_mutex_waiter *waiter)
210{
211	memset(waiter, 0x11, sizeof(*waiter));
212	plist_node_init(&waiter->list_entry, MAX_PRIO);
213	plist_node_init(&waiter->pi_list_entry, MAX_PRIO);
214}
215
216void debug_rt_mutex_free_waiter(struct rt_mutex_waiter *waiter)
217{
218	TRACE_WARN_ON(!plist_node_empty(&waiter->list_entry));
219	TRACE_WARN_ON(!plist_node_empty(&waiter->pi_list_entry));
220	TRACE_WARN_ON(waiter->task);
221	memset(waiter, 0x22, sizeof(*waiter));
222}
223
224void debug_rt_mutex_init(struct rt_mutex *lock, const char *name)
225{
226	/*
227	 * Make sure we are not reinitializing a held lock:
228	 */
229	debug_check_no_locks_freed((void *)lock, sizeof(*lock));
230	lock->name = name;
231}
232
233void
234rt_mutex_deadlock_account_lock(struct rt_mutex *lock, struct task_struct *task)
235{
236}
237
238void rt_mutex_deadlock_account_unlock(struct task_struct *task)
239{
240}
241