Merge branch 'fixes-gpio-to-irq' into fixes
[platform/adaptation/renesas_rcar/renesas_kernel.git] / kernel / hung_task.c
1 /*
2  * Detect Hung Task
3  *
4  * kernel/hung_task.c - kernel thread for detecting tasks stuck in D state
5  *
6  */
7
8 #include <linux/mm.h>
9 #include <linux/cpu.h>
10 #include <linux/nmi.h>
11 #include <linux/init.h>
12 #include <linux/delay.h>
13 #include <linux/freezer.h>
14 #include <linux/kthread.h>
15 #include <linux/lockdep.h>
16 #include <linux/export.h>
17 #include <linux/sysctl.h>
18
19 /*
20  * The number of tasks checked:
21  */
22 unsigned long __read_mostly sysctl_hung_task_check_count = PID_MAX_LIMIT;
23
24 /*
25  * Limit number of tasks checked in a batch.
26  *
27  * This value controls the preemptibility of khungtaskd since preemption
28  * is disabled during the critical section. It also controls the size of
29  * the RCU grace period. So it needs to be upper-bound.
30  */
31 #define HUNG_TASK_BATCHING 1024
32
33 /*
34  * Zero means infinite timeout - no checking done:
35  */
36 unsigned long __read_mostly sysctl_hung_task_timeout_secs = CONFIG_DEFAULT_HUNG_TASK_TIMEOUT;
37
38 unsigned long __read_mostly sysctl_hung_task_warnings = 10;
39
40 static int __read_mostly did_panic;
41
42 static struct task_struct *watchdog_task;
43
44 /*
45  * Should we panic (and reboot, if panic_timeout= is set) when a
46  * hung task is detected:
47  */
48 unsigned int __read_mostly sysctl_hung_task_panic =
49                                 CONFIG_BOOTPARAM_HUNG_TASK_PANIC_VALUE;
50
51 static int __init hung_task_panic_setup(char *str)
52 {
53         sysctl_hung_task_panic = simple_strtoul(str, NULL, 0);
54
55         return 1;
56 }
57 __setup("hung_task_panic=", hung_task_panic_setup);
58
59 static int
60 hung_task_panic(struct notifier_block *this, unsigned long event, void *ptr)
61 {
62         did_panic = 1;
63
64         return NOTIFY_DONE;
65 }
66
67 static struct notifier_block panic_block = {
68         .notifier_call = hung_task_panic,
69 };
70
71 static void check_hung_task(struct task_struct *t, unsigned long timeout)
72 {
73         unsigned long switch_count = t->nvcsw + t->nivcsw;
74
75         /*
76          * Ensure the task is not frozen.
77          * Also, skip vfork and any other user process that freezer should skip.
78          */
79         if (unlikely(t->flags & (PF_FROZEN | PF_FREEZER_SKIP)))
80             return;
81
82         /*
83          * When a freshly created task is scheduled once, changes its state to
84          * TASK_UNINTERRUPTIBLE without having ever been switched out once, it
85          * musn't be checked.
86          */
87         if (unlikely(!switch_count))
88                 return;
89
90         if (switch_count != t->last_switch_count) {
91                 t->last_switch_count = switch_count;
92                 return;
93         }
94         if (!sysctl_hung_task_warnings)
95                 return;
96         sysctl_hung_task_warnings--;
97
98         /*
99          * Ok, the task did not get scheduled for more than 2 minutes,
100          * complain:
101          */
102         printk(KERN_ERR "INFO: task %s:%d blocked for more than "
103                         "%ld seconds.\n", t->comm, t->pid, timeout);
104         printk(KERN_ERR "\"echo 0 > /proc/sys/kernel/hung_task_timeout_secs\""
105                         " disables this message.\n");
106         sched_show_task(t);
107         debug_show_held_locks(t);
108
109         touch_nmi_watchdog();
110
111         if (sysctl_hung_task_panic)
112                 panic("hung_task: blocked tasks");
113 }
114
115 /*
116  * To avoid extending the RCU grace period for an unbounded amount of time,
117  * periodically exit the critical section and enter a new one.
118  *
119  * For preemptible RCU it is sufficient to call rcu_read_unlock in order
120  * to exit the grace period. For classic RCU, a reschedule is required.
121  */
122 static bool rcu_lock_break(struct task_struct *g, struct task_struct *t)
123 {
124         bool can_cont;
125
126         get_task_struct(g);
127         get_task_struct(t);
128         rcu_read_unlock();
129         cond_resched();
130         rcu_read_lock();
131         can_cont = pid_alive(g) && pid_alive(t);
132         put_task_struct(t);
133         put_task_struct(g);
134
135         return can_cont;
136 }
137
138 /*
139  * Check whether a TASK_UNINTERRUPTIBLE does not get woken up for
140  * a really long time (120 seconds). If that happens, print out
141  * a warning.
142  */
143 static void check_hung_uninterruptible_tasks(unsigned long timeout)
144 {
145         int max_count = sysctl_hung_task_check_count;
146         int batch_count = HUNG_TASK_BATCHING;
147         struct task_struct *g, *t;
148
149         /*
150          * If the system crashed already then all bets are off,
151          * do not report extra hung tasks:
152          */
153         if (test_taint(TAINT_DIE) || did_panic)
154                 return;
155
156         rcu_read_lock();
157         do_each_thread(g, t) {
158                 if (!max_count--)
159                         goto unlock;
160                 if (!--batch_count) {
161                         batch_count = HUNG_TASK_BATCHING;
162                         if (!rcu_lock_break(g, t))
163                                 goto unlock;
164                 }
165                 /* use "==" to skip the TASK_KILLABLE tasks waiting on NFS */
166                 if (t->state == TASK_UNINTERRUPTIBLE)
167                         check_hung_task(t, timeout);
168         } while_each_thread(g, t);
169  unlock:
170         rcu_read_unlock();
171 }
172
173 static unsigned long timeout_jiffies(unsigned long timeout)
174 {
175         /* timeout of 0 will disable the watchdog */
176         return timeout ? timeout * HZ : MAX_SCHEDULE_TIMEOUT;
177 }
178
179 /*
180  * Process updating of timeout sysctl
181  */
182 int proc_dohung_task_timeout_secs(struct ctl_table *table, int write,
183                                   void __user *buffer,
184                                   size_t *lenp, loff_t *ppos)
185 {
186         int ret;
187
188         ret = proc_doulongvec_minmax(table, write, buffer, lenp, ppos);
189
190         if (ret || !write)
191                 goto out;
192
193         wake_up_process(watchdog_task);
194
195  out:
196         return ret;
197 }
198
199 /*
200  * kthread which checks for tasks stuck in D state
201  */
202 static int watchdog(void *dummy)
203 {
204         set_user_nice(current, 0);
205
206         for ( ; ; ) {
207                 unsigned long timeout = sysctl_hung_task_timeout_secs;
208
209                 while (schedule_timeout_interruptible(timeout_jiffies(timeout)))
210                         timeout = sysctl_hung_task_timeout_secs;
211
212                 check_hung_uninterruptible_tasks(timeout);
213         }
214
215         return 0;
216 }
217
218 static int __init hung_task_init(void)
219 {
220         atomic_notifier_chain_register(&panic_notifier_list, &panic_block);
221         watchdog_task = kthread_run(watchdog, NULL, "khungtaskd");
222
223         return 0;
224 }
225
226 module_init(hung_task_init);