kernel/locking/rtmutex-debug.c

   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/sched/debug.h>
  22 #include <linux/delay.h>
  23 #include <linux/export.h>
  24 #include <linux/spinlock.h>
  25 #include <linux/kallsyms.h>
  26 #include <linux/syscalls.h>
  27 #include <linux/interrupt.h>
  28 #include <linux/rbtree.h>
  29 #include <linux/fs.h>
  30 #include <linux/debug_locks.h>
  31
  32 #include "rtmutex_common.h"
  33
  34 static void printk_task(struct task_struct *p)
  35 {
  36         if (p)
  37                 printk("%16s:%5d [%p, %3d]", p->comm, task_pid_nr(p), p, p->prio);
  38         else
  39                 printk("<none>");
  40 }
  41
  42 static void printk_lock(struct rt_mutex *lock, int print_owner)
  43 {
  44         if (lock->name)
  45                 printk(" [%p] {%s}\n",
  46                         lock, lock->name);
  47         else
  48                 printk(" [%p] {%s:%d}\n",
  49                         lock, lock->file, lock->line);
  50
  51         if (print_owner && rt_mutex_owner(lock)) {
  52                 printk(".. ->owner: %p\n", lock->owner);
  53                 printk(".. held by:  ");
  54                 printk_task(rt_mutex_owner(lock));
  55                 printk("\n");
  56         }
  57 }
  58
  59 void rt_mutex_debug_task_free(struct task_struct *task)
  60 {
  61         DEBUG_LOCKS_WARN_ON(!RB_EMPTY_ROOT(&task->pi_waiters));
  62         DEBUG_LOCKS_WARN_ON(task->pi_blocked_on);
  63 }
  64
  65 /*
  66  * We fill out the fields in the waiter to store the information about
  67  * the deadlock. We print when we return. act_waiter can be NULL in
  68  * case of a remove waiter operation.
  69  */
  70 void debug_rt_mutex_deadlock(enum rtmutex_chainwalk chwalk,
  71                              struct rt_mutex_waiter *act_waiter,
  72                              struct rt_mutex *lock)
  73 {
  74         struct task_struct *task;
  75
  76         if (!debug_locks || chwalk == RT_MUTEX_FULL_CHAINWALK || !act_waiter)
  77                 return;
  78
  79         task = rt_mutex_owner(act_waiter->lock);
  80         if (task && task != current) {
  81                 act_waiter->deadlock_task_pid = get_pid(task_pid(task));
  82                 act_waiter->deadlock_lock = lock;
  83         }
  84 }
  85
  86 void debug_rt_mutex_print_deadlock(struct rt_mutex_waiter *waiter)
  87 {
  88         struct task_struct *task;
  89
  90         if (!waiter->deadlock_lock || !debug_locks)
  91                 return;
  92
  93         rcu_read_lock();
  94         task = pid_task(waiter->deadlock_task_pid, PIDTYPE_PID);
  95         if (!task) {
  96                 rcu_read_unlock();
  97                 return;
  98         }
  99
 100         if (!debug_locks_off()) {
 101                 rcu_read_unlock();
 102                 return;
 103         }
 104
 105         printk("\n============================================\n");
 106         printk(  "[ BUG: circular locking deadlock detected! ]\n");
 107         printk("%s\n", print_tainted());
 108         printk(  "--------------------------------------------\n");
 109         printk("%s/%d is deadlocking current task %s/%d\n\n",
 110                task->comm, task_pid_nr(task),
 111                current->comm, task_pid_nr(current));
 112
 113         printk("\n1) %s/%d is trying to acquire this lock:\n",
 114                current->comm, task_pid_nr(current));
 115         printk_lock(waiter->lock, 1);
 116
 117         printk("\n2) %s/%d is blocked on this lock:\n",
 118                 task->comm, task_pid_nr(task));
 119         printk_lock(waiter->deadlock_lock, 1);
 120
 121         debug_show_held_locks(current);
 122         debug_show_held_locks(task);
 123
 124         printk("\n%s/%d's [blocked] stackdump:\n\n",
 125                 task->comm, task_pid_nr(task));
 126         show_stack(task, NULL);
 127         printk("\n%s/%d's [current] stackdump:\n\n",
 128                 current->comm, task_pid_nr(current));
 129         dump_stack();
 130         debug_show_all_locks();
 131         rcu_read_unlock();
 132
 133         printk("[ turning off deadlock detection."
 134                "Please report this trace. ]\n\n");
 135 }
 136
 137 void debug_rt_mutex_lock(struct rt_mutex *lock)
 138 {
 139 }
 140
 141 void debug_rt_mutex_unlock(struct rt_mutex *lock)
 142 {
 143         DEBUG_LOCKS_WARN_ON(rt_mutex_owner(lock) != current);
 144 }
 145
 146 void
 147 debug_rt_mutex_proxy_lock(struct rt_mutex *lock, struct task_struct *powner)
 148 {
 149 }
 150
 151 void debug_rt_mutex_proxy_unlock(struct rt_mutex *lock)
 152 {
 153         DEBUG_LOCKS_WARN_ON(!rt_mutex_owner(lock));
 154 }
 155
 156 void debug_rt_mutex_init_waiter(struct rt_mutex_waiter *waiter)
 157 {
 158         memset(waiter, 0x11, sizeof(*waiter));
 159         waiter->deadlock_task_pid = NULL;
 160 }
 161
 162 void debug_rt_mutex_free_waiter(struct rt_mutex_waiter *waiter)
 163 {
 164         put_pid(waiter->deadlock_task_pid);
 165         memset(waiter, 0x22, sizeof(*waiter));
 166 }
 167
 168 void debug_rt_mutex_init(struct rt_mutex *lock, const char *name)
 169 {
 170         /*
 171          * Make sure we are not reinitializing a held lock:
 172          */
 173         debug_check_no_locks_freed((void *)lock, sizeof(*lock));
 174         lock->name = name;
 175 }
 176