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
 32static 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
 40static 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
 57void 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 */
 68void 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
 83void 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
134void debug_rt_mutex_lock(struct rt_mutex *lock)
135{
136}
137
138void debug_rt_mutex_unlock(struct rt_mutex *lock)
139{
140	DEBUG_LOCKS_WARN_ON(rt_mutex_owner(lock) != current);
141}
142
143void
144debug_rt_mutex_proxy_lock(struct rt_mutex *lock, struct task_struct *powner)
145{
146}
147
148void debug_rt_mutex_proxy_unlock(struct rt_mutex *lock)
149{
150	DEBUG_LOCKS_WARN_ON(!rt_mutex_owner(lock));
151}
152
153void 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
161void 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
169void 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
178void
179rt_mutex_deadlock_account_lock(struct rt_mutex *lock, struct task_struct *task)
180{
181}
182
183void rt_mutex_deadlock_account_unlock(struct task_struct *task)
184{
185}
186