diff options
author | Ingo Molnar <mingo@elte.hu> | 2009-04-08 10:35:30 +0200 |
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committer | Ingo Molnar <mingo@elte.hu> | 2009-04-08 10:35:30 +0200 |
commit | 5ea472a77f8e4811ceee3f44a9deda6ad6e8b789 (patch) | |
tree | a9ec5019e2b666a19874fc344ffb0dd5da6bce94 /kernel/hung_task.c | |
parent | 6c009ecef8cca28c7c09eb16d0802e37915a76e1 (diff) | |
parent | 577c9c456f0e1371cbade38eaf91ae8e8a308555 (diff) |
Merge commit 'v2.6.30-rc1' into perfcounters/core
Conflicts:
arch/powerpc/include/asm/systbl.h
arch/powerpc/include/asm/unistd.h
include/linux/init_task.h
Merge reason: the conflicts are non-trivial: PowerPC placement
of sys_perf_counter_open has to be mixed with the
new preadv/pwrite syscalls.
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Diffstat (limited to 'kernel/hung_task.c')
-rw-r--r-- | kernel/hung_task.c | 217 |
1 files changed, 217 insertions, 0 deletions
diff --git a/kernel/hung_task.c b/kernel/hung_task.c new file mode 100644 index 00000000000..022a4927b78 --- /dev/null +++ b/kernel/hung_task.c @@ -0,0 +1,217 @@ +/* + * Detect Hung Task + * + * kernel/hung_task.c - kernel thread for detecting tasks stuck in D state + * + */ + +#include <linux/mm.h> +#include <linux/cpu.h> +#include <linux/nmi.h> +#include <linux/init.h> +#include <linux/delay.h> +#include <linux/freezer.h> +#include <linux/kthread.h> +#include <linux/lockdep.h> +#include <linux/module.h> +#include <linux/sysctl.h> + +/* + * The number of tasks checked: + */ +unsigned long __read_mostly sysctl_hung_task_check_count = PID_MAX_LIMIT; + +/* + * Limit number of tasks checked in a batch. + * + * This value controls the preemptibility of khungtaskd since preemption + * is disabled during the critical section. It also controls the size of + * the RCU grace period. So it needs to be upper-bound. + */ +#define HUNG_TASK_BATCHING 1024 + +/* + * Zero means infinite timeout - no checking done: + */ +unsigned long __read_mostly sysctl_hung_task_timeout_secs = 120; + +unsigned long __read_mostly sysctl_hung_task_warnings = 10; + +static int __read_mostly did_panic; + +static struct task_struct *watchdog_task; + +/* + * Should we panic (and reboot, if panic_timeout= is set) when a + * hung task is detected: + */ +unsigned int __read_mostly sysctl_hung_task_panic = + CONFIG_BOOTPARAM_HUNG_TASK_PANIC_VALUE; + +static int __init hung_task_panic_setup(char *str) +{ + sysctl_hung_task_panic = simple_strtoul(str, NULL, 0); + + return 1; +} +__setup("hung_task_panic=", hung_task_panic_setup); + +static int +hung_task_panic(struct notifier_block *this, unsigned long event, void *ptr) +{ + did_panic = 1; + + return NOTIFY_DONE; +} + +static struct notifier_block panic_block = { + .notifier_call = hung_task_panic, +}; + +static void check_hung_task(struct task_struct *t, unsigned long timeout) +{ + unsigned long switch_count = t->nvcsw + t->nivcsw; + + /* + * Ensure the task is not frozen. + * Also, when a freshly created task is scheduled once, changes + * its state to TASK_UNINTERRUPTIBLE without having ever been + * switched out once, it musn't be checked. + */ + if (unlikely(t->flags & PF_FROZEN || !switch_count)) + return; + + if (switch_count != t->last_switch_count) { + t->last_switch_count = switch_count; + return; + } + if (!sysctl_hung_task_warnings) + return; + sysctl_hung_task_warnings--; + + /* + * Ok, the task did not get scheduled for more than 2 minutes, + * complain: + */ + printk(KERN_ERR "INFO: task %s:%d blocked for more than " + "%ld seconds.\n", t->comm, t->pid, timeout); + printk(KERN_ERR "\"echo 0 > /proc/sys/kernel/hung_task_timeout_secs\"" + " disables this message.\n"); + sched_show_task(t); + __debug_show_held_locks(t); + + touch_nmi_watchdog(); + + if (sysctl_hung_task_panic) + panic("hung_task: blocked tasks"); +} + +/* + * To avoid extending the RCU grace period for an unbounded amount of time, + * periodically exit the critical section and enter a new one. + * + * For preemptible RCU it is sufficient to call rcu_read_unlock in order + * exit the grace period. For classic RCU, a reschedule is required. + */ +static void rcu_lock_break(struct task_struct *g, struct task_struct *t) +{ + get_task_struct(g); + get_task_struct(t); + rcu_read_unlock(); + cond_resched(); + rcu_read_lock(); + put_task_struct(t); + put_task_struct(g); +} + +/* + * Check whether a TASK_UNINTERRUPTIBLE does not get woken up for + * a really long time (120 seconds). If that happens, print out + * a warning. + */ +static void check_hung_uninterruptible_tasks(unsigned long timeout) +{ + int max_count = sysctl_hung_task_check_count; + int batch_count = HUNG_TASK_BATCHING; + struct task_struct *g, *t; + + /* + * If the system crashed already then all bets are off, + * do not report extra hung tasks: + */ + if (test_taint(TAINT_DIE) || did_panic) + return; + + rcu_read_lock(); + do_each_thread(g, t) { + if (!--max_count) + goto unlock; + if (!--batch_count) { + batch_count = HUNG_TASK_BATCHING; + rcu_lock_break(g, t); + /* Exit if t or g was unhashed during refresh. */ + if (t->state == TASK_DEAD || g->state == TASK_DEAD) + goto unlock; + } + /* use "==" to skip the TASK_KILLABLE tasks waiting on NFS */ + if (t->state == TASK_UNINTERRUPTIBLE) + check_hung_task(t, timeout); + } while_each_thread(g, t); + unlock: + rcu_read_unlock(); +} + +static unsigned long timeout_jiffies(unsigned long timeout) +{ + /* timeout of 0 will disable the watchdog */ + return timeout ? timeout * HZ : MAX_SCHEDULE_TIMEOUT; +} + +/* + * Process updating of timeout sysctl + */ +int proc_dohung_task_timeout_secs(struct ctl_table *table, int write, + struct file *filp, void __user *buffer, + size_t *lenp, loff_t *ppos) +{ + int ret; + + ret = proc_doulongvec_minmax(table, write, filp, buffer, lenp, ppos); + + if (ret || !write) + goto out; + + wake_up_process(watchdog_task); + + out: + return ret; +} + +/* + * kthread which checks for tasks stuck in D state + */ +static int watchdog(void *dummy) +{ + set_user_nice(current, 0); + + for ( ; ; ) { + unsigned long timeout = sysctl_hung_task_timeout_secs; + + while (schedule_timeout_interruptible(timeout_jiffies(timeout))) + timeout = sysctl_hung_task_timeout_secs; + + check_hung_uninterruptible_tasks(timeout); + } + + return 0; +} + +static int __init hung_task_init(void) +{ + atomic_notifier_chain_register(&panic_notifier_list, &panic_block); + watchdog_task = kthread_run(watchdog, NULL, "khungtaskd"); + + return 0; +} + +module_init(hung_task_init); |