全部博文（108）
分类： 系统运维
2013-12-09 10:21:03
| 001 | /** |
| 002 | * Detect Hung Task |
| 003 | * |
| 004 | * kernel/hung_task.c - kernel thread for detecting tasks stuck in D state |
| 005 | * |
| 006 | */ |
| 007 |
| 008 |
#include |
| 009 |
#include |
| 010 |
#include |
| 011 |
#include |
| 012 |
#include |
| 013 |
#include |
| 014 |
#include |
| 015 |
#include |
| 016 |
#include |
| 017 |
#include |
| 018 |
| 019 | /** |
| 020 | * The number of tasks checked: |
| 021 | */ |
| 022 | unsigned long __read_mostly sysctl_hung_task_check_count = PID_MAX_LIMIT; |
| 023 |
| 024 | /** |
| 025 | * Limit number of tasks checked in a batch. |
| 026 | * |
| 027 | * This value controls the preemptibility of khungtaskd since preemption |
| 028 | * is disabled during the critical section. It also controls the size of |
| 029 | * the RCU grace period. So it needs to be upper-bound. |
| 030 | */ |
| 031 | #define HUNG_TASK_BATCHING 1024 |
| 032 |
| 033 | /** |
| 034 | * Zero means infinite timeout - no checking done: |
| 035 | */ |
| 036 | unsigned long __read_mostly sysctl_hung_task_timeout_secs = 120; |
| 037 |
| 038 | unsigned long __read_mostly sysctl_hung_task_warnings = 10; |
| 039 |
| 040 | static int __read_mostly did_panic; |
| 041 |
| 042 | static struct task_struct *watchdog_task; |
| 043 |
| 044 | /** |
| 045 | * Should we panic (and reboot, if panic_timeout= is set) when a |
| 046 | * hung task is detected: |
| 047 | */ |
| 048 | unsigned int __read_mostly sysctl_hung_task_panic = |
| 049 | CONFIG_BOOTPARAM_HUNG_TASK_PANIC_VALUE; |
| 050 |
| 051 | static int __init hung_task_panic_setup(char *str) |
| 052 | { |
| 053 | sysctl_hung_task_panic = simple_strtoul(str, NULL, 0); |
| 054 |
| 055 | return 1; |
| 056 | } |
| 057 | __setup("hung_task_panic=", hung_task_panic_setup); |
| 058 |
| 059 | static int |
| 060 | hung_task_panic(struct notifier_block *this, unsigned long event, void *ptr) |
| 061 | { |
| 062 | did_panic = 1; |
| 063 |
| 064 | return NOTIFY_DONE; |
| 065 | } |
| 066 |
| 067 | static struct notifier_block panic_block = { |
| 068 | .notifier_call = hung_task_panic, |
| 069 | }; |
| 070 |
| 071 | static void check_hung_task(struct task_struct *t, unsigned long timeout) |
| 072 | { |
| 073 | unsigned long switch_count = t->nvcsw + t->nivcsw; |
| 074 |
| 075 | /** |
| 076 | * Ensure the task is not frozen. |
| 077 | * Also, when a freshly created task is scheduled once, changes |
| 078 | * its state to TASK_UNINTERRUPTIBLE without having ever been |
| 079 | * switched out once, it musn't be checked. |
| 080 | */ |
| 081 | if (unlikely(t->flags & PF_FROZEN || !switch_count)) |
| 082 | return; |
| 083 |
| 084 | if (switch_count != t->last_switch_count) { |
| 085 | t->last_switch_count = switch_count; |
| 086 | return; |
| 087 | } |
| 088 | if (!sysctl_hung_task_warnings) |
| 089 | return; |
| 090 | sysctl_hung_task_warnings--; |
| 091 |
| 092 | /** |
| 093 | * Ok, the task did not get scheduled for more than 2 minutes, |
| 094 | * complain: |
| 095 | */ |
| 096 | printk(KERN_ERR "INFO: task %s:%d blocked for more than " |
| 097 | "%ld seconds.\n", t->comm, t->pid, timeout); |
| 098 | printk(KERN_ERR "\"echo 0 > /proc/sys/kernel/hung_task_timeout_secs\"" |
| 099 | " disables this message.\n"); |
| 100 | sched_show_task(t); |
| 101 | __debug_show_held_locks(t); |
| 102 |
| 103 | touch_nmi_watchdog(); |
| 104 |
| 105 | if (sysctl_hung_task_panic) |
| 106 | panic("hung_task: blocked tasks"); |
| 107 | } |
| 108 |
| 109 | /** |
| 110 | * To avoid extending the RCU grace period for an unbounded amount of time, |
| 111 | * periodically exit the critical section and enter a new one. |
| 112 | * |
| 113 | * For preemptible RCU it is sufficient to call rcu_read_unlock in order |
| 114 | * exit the grace period. For classic RCU, a reschedule is required. |
| 115 | */ |
| 116 | static void rcu_lock_break(struct task_struct *g, struct task_struct *t) |
| 117 | { |
| 118 | get_task_struct(g); |
| 119 | get_task_struct(t); |
| 120 | rcu_read_unlock(); |
| 121 | cond_resched(); |
| 122 | rcu_read_lock(); |
| 123 | put_task_struct(t); |
| 124 | put_task_struct(g); |
| 125 | } |
| 126 |
| 127 | /** |
| 128 | * Check whether a TASK_UNINTERRUPTIBLE does not get woken up for |
| 129 | * a really long time (120 seconds). If that happens, print out |
| 130 | * a warning. |
| 131 | */ |
| 132 | static void check_hung_uninterruptible_tasks(unsigned long timeout) |
| 133 | { |
| 134 | int max_count = sysctl_hung_task_check_count; |
| 135 | int batch_count = HUNG_TASK_BATCHING; |
| 136 | struct task_struct *g, *t; |
| 137 |
| 138 | /** |
| 139 | * If the system crashed already then all bets are off, |
| 140 | * do not report extra hung tasks: |
| 141 | */ |
| 142 | if (test_taint(TAINT_DIE) || did_panic) |
| 143 | return; |
| 144 |
| 145 | rcu_read_lock(); |
| 146 | do_each_thread(g, t) { |
| 147 | if (!max_count--) |
| 148 | goto unlock; |
| 149 | if (!--batch_count) { |
| 150 | batch_count = HUNG_TASK_BATCHING; |
| 151 | rcu_lock_break(g, t); |
| 152 | /** Exit if t or g was unhashed during refresh. */ |
| 153 | if (t->state == TASK_DEAD || g->state == TASK_DEAD) |
| 154 | goto unlock; |
| 155 | } |
| 156 | /** use "==" to skip the TASK_KILLABLE tasks waiting on NFS */ |
| 157 | if (t->state == TASK_UNINTERRUPTIBLE) |
| 158 | check_hung_task(t, timeout); |
| 159 | } while_each_thread(g, t); |
| 160 | unlock: |
| 161 | rcu_read_unlock(); |
| 162 | } |
| 163 |
| 164 | static unsigned long timeout_jiffies(unsigned long timeout) |
| 165 | { |
| 166 | /** timeout of 0 will disable the watchdog */ |
| 167 | return timeout ? timeout * HZ : MAX_SCHEDULE_TIMEOUT; |
| 168 | } |
| 169 |
| 170 | /** |
| 171 | * Process updating of timeout sysctl |
| 172 | */ |
| 173 | int proc_dohung_task_timeout_secs(struct ctl_table *table, int write, |
| 174 | void __user *buffer, |
| 175 | size_t *lenp, loff_t *ppos) |
| 176 | { |
| 177 | int ret; |
| 178 |
| 179 | ret = proc_doulongvec_minmax(table, write, buffer, lenp, ppos); |
| 180 |
| 181 | if (ret || !write) |
| 182 | goto out; |
| 183 |
| 184 | wake_up_process(watchdog_task); |
| 185 |
| 186 | out: |
| 187 | return ret; |
| 188 | } |
| 189 |
| 190 | /** |
| 191 | * kthread which checks for tasks stuck in D state |
| 192 | */ |
| 193 | static int watchdog(void *dummy) |
