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/delay.h>
 22#include <linux/export.h>
 23#include <linux/spinlock.h>
 24#include <linux/kallsyms.h>
 25#include <linux/syscalls.h>
 26#include <linux/interrupt.h>
 27#include <linux/rbtree.h>
 28#include <linux/fs.h>
 29#include <linux/debug_locks.h>
 30
 31#include "rtmutex_common.h"
 32
 33static void printk_task(struct task_struct *p)
 34{
 35	if (p)
 36		printk("%16s:%5d [%p, %3d]", p->comm, task_pid_nr(p), p, p->prio);
 37	else
 38		printk("<none>");
 39}
 40
 41static void printk_lock(struct rt_mutex *lock, int print_owner)
 42{
 43	if (lock->name)
 44		printk(" [%p] {%s}\n",
 45			lock, lock->name);
 46	else
 47		printk(" [%p] {%s:%d}\n",
 48			lock, lock->file, lock->line);
 49
 50	if (print_owner && rt_mutex_owner(lock)) {
 51		printk(".. ->owner: %p\n", lock->owner);
 52		printk(".. held by:  ");
 53		printk_task(rt_mutex_owner(lock));
 54		printk("\n");
 55	}
 56}
 57
 58void rt_mutex_debug_task_free(struct task_struct *task)
 59{
 60	DEBUG_LOCKS_WARN_ON(!RB_EMPTY_ROOT(&task->pi_waiters));
 61	DEBUG_LOCKS_WARN_ON(task->pi_blocked_on);
 62}
 63
 64/*
 65 * We fill out the fields in the waiter to store the information about
 66 * the deadlock. We print when we return. act_waiter can be NULL in
 67 * case of a remove waiter operation.
 68 */
 69void debug_rt_mutex_deadlock(enum rtmutex_chainwalk chwalk,
 70			     struct rt_mutex_waiter *act_waiter,
 71			     struct rt_mutex *lock)
 72{
 73	struct task_struct *task;
 74
 75	if (!debug_locks || chwalk == RT_MUTEX_FULL_CHAINWALK || !act_waiter)
 76		return;
 77
 78	task = rt_mutex_owner(act_waiter->lock);
 79	if (task && task != current) {
 80		act_waiter->deadlock_task_pid = get_pid(task_pid(task));
 81		act_waiter->deadlock_lock = lock;
 82	}
 83}
 84
 85void debug_rt_mutex_print_deadlock(struct rt_mutex_waiter *waiter)
 86{
 87	struct task_struct *task;
 88
 89	if (!waiter->deadlock_lock || !debug_locks)
 90		return;
 91
 92	rcu_read_lock();
 93	task = pid_task(waiter->deadlock_task_pid, PIDTYPE_PID);
 94	if (!task) {
 95		rcu_read_unlock();
 96		return;
 97	}
 98
 99	if (!debug_locks_off()) {
100		rcu_read_unlock();
101		return;
102	}
103
104	printk("\n============================================\n");
105	printk(  "[ BUG: circular locking deadlock detected! ]\n");
106	printk("%s\n", print_tainted());
107	printk(  "--------------------------------------------\n");
108	printk("%s/%d is deadlocking current task %s/%d\n\n",
109	       task->comm, task_pid_nr(task),
110	       current->comm, task_pid_nr(current));
111
112	printk("\n1) %s/%d is trying to acquire this lock:\n",
113	       current->comm, task_pid_nr(current));
114	printk_lock(waiter->lock, 1);
115
116	printk("\n2) %s/%d is blocked on this lock:\n",
117		task->comm, task_pid_nr(task));
118	printk_lock(waiter->deadlock_lock, 1);
119
120	debug_show_held_locks(current);
121	debug_show_held_locks(task);
122
123	printk("\n%s/%d's [blocked] stackdump:\n\n",
124		task->comm, task_pid_nr(task));
125	show_stack(task, NULL);
126	printk("\n%s/%d's [current] stackdump:\n\n",
127		current->comm, task_pid_nr(current));
128	dump_stack();
129	debug_show_all_locks();
130	rcu_read_unlock();
131
132	printk("[ turning off deadlock detection."
133	       "Please report this trace. ]\n\n");
134}
135
136void debug_rt_mutex_lock(struct rt_mutex *lock)
137{
138}
139
140void debug_rt_mutex_unlock(struct rt_mutex *lock)
141{
142	DEBUG_LOCKS_WARN_ON(rt_mutex_owner(lock) != current);
143}
144
145void
146debug_rt_mutex_proxy_lock(struct rt_mutex *lock, struct task_struct *powner)
147{
148}
149
150void debug_rt_mutex_proxy_unlock(struct rt_mutex *lock)
151{
152	DEBUG_LOCKS_WARN_ON(!rt_mutex_owner(lock));
153}
154
155void debug_rt_mutex_init_waiter(struct rt_mutex_waiter *waiter)
156{
157	memset(waiter, 0x11, sizeof(*waiter));
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	memset(waiter, 0x22, sizeof(*waiter));
165}
166
167void debug_rt_mutex_init(struct rt_mutex *lock, const char *name)
168{
169	/*
170	 * Make sure we are not reinitializing a held lock:
171	 */
172	debug_check_no_locks_freed((void *)lock, sizeof(*lock));
173	lock->name = name;
174}
175
176void
177rt_mutex_deadlock_account_lock(struct rt_mutex *lock, struct task_struct *task)
178{
179}
180
181void rt_mutex_deadlock_account_unlock(struct task_struct *task)
182{
183}
184