diff options
Diffstat (limited to 'kernel/softlockup.c')
| -rw-r--r-- | kernel/softlockup.c | 151 |
1 files changed, 151 insertions, 0 deletions
diff --git a/kernel/softlockup.c b/kernel/softlockup.c new file mode 100644 index 00000000000..75976209cea --- /dev/null +++ b/kernel/softlockup.c @@ -0,0 +1,151 @@ +/* + * Detect Soft Lockups + * + * started by Ingo Molnar, (C) 2005, Red Hat + * + * this code detects soft lockups: incidents in where on a CPU + * the kernel does not reschedule for 10 seconds or more. + */ + +#include <linux/mm.h> +#include <linux/cpu.h> +#include <linux/init.h> +#include <linux/delay.h> +#include <linux/kthread.h> +#include <linux/notifier.h> +#include <linux/module.h> + +static DEFINE_SPINLOCK(print_lock); + +static DEFINE_PER_CPU(unsigned long, timestamp) = 0; +static DEFINE_PER_CPU(unsigned long, print_timestamp) = 0; +static DEFINE_PER_CPU(struct task_struct *, watchdog_task); + +static int did_panic = 0; +static int softlock_panic(struct notifier_block *this, unsigned long event, + void *ptr) +{ + did_panic = 1; + + return NOTIFY_DONE; +} + +static struct notifier_block panic_block = { + .notifier_call = softlock_panic, +}; + +void touch_softlockup_watchdog(void) +{ + per_cpu(timestamp, raw_smp_processor_id()) = jiffies; +} +EXPORT_SYMBOL(touch_softlockup_watchdog); + +/* + * This callback runs from the timer interrupt, and checks + * whether the watchdog thread has hung or not: + */ +void softlockup_tick(struct pt_regs *regs) +{ + int this_cpu = smp_processor_id(); + unsigned long timestamp = per_cpu(timestamp, this_cpu); + + if (per_cpu(print_timestamp, this_cpu) == timestamp) + return; + + /* Do not cause a second panic when there already was one */ + if (did_panic) + return; + + if (time_after(jiffies, timestamp + 10*HZ)) { + per_cpu(print_timestamp, this_cpu) = timestamp; + + spin_lock(&print_lock); + printk(KERN_ERR "BUG: soft lockup detected on CPU#%d!\n", + this_cpu); + show_regs(regs); + spin_unlock(&print_lock); + } +} + +/* + * The watchdog thread - runs every second and touches the timestamp. + */ +static int watchdog(void * __bind_cpu) +{ + struct sched_param param = { .sched_priority = 99 }; + int this_cpu = (long) __bind_cpu; + + printk("softlockup thread %d started up.\n", this_cpu); + + sched_setscheduler(current, SCHED_FIFO, ¶m); + current->flags |= PF_NOFREEZE; + + set_current_state(TASK_INTERRUPTIBLE); + + /* + * Run briefly once per second - if this gets delayed for + * more than 10 seconds then the debug-printout triggers + * in softlockup_tick(): + */ + while (!kthread_should_stop()) { + msleep_interruptible(1000); + touch_softlockup_watchdog(); + } + __set_current_state(TASK_RUNNING); + + return 0; +} + +/* + * Create/destroy watchdog threads as CPUs come and go: + */ +static int __devinit +cpu_callback(struct notifier_block *nfb, unsigned long action, void *hcpu) +{ + int hotcpu = (unsigned long)hcpu; + struct task_struct *p; + + switch (action) { + case CPU_UP_PREPARE: + BUG_ON(per_cpu(watchdog_task, hotcpu)); + p = kthread_create(watchdog, hcpu, "watchdog/%d", hotcpu); + if (IS_ERR(p)) { + printk("watchdog for %i failed\n", hotcpu); + return NOTIFY_BAD; + } + per_cpu(watchdog_task, hotcpu) = p; + kthread_bind(p, hotcpu); + break; + case CPU_ONLINE: + + wake_up_process(per_cpu(watchdog_task, hotcpu)); + break; +#ifdef CONFIG_HOTPLUG_CPU + case CPU_UP_CANCELED: + /* Unbind so it can run. Fall thru. */ + kthread_bind(per_cpu(watchdog_task, hotcpu), smp_processor_id()); + case CPU_DEAD: + p = per_cpu(watchdog_task, hotcpu); + per_cpu(watchdog_task, hotcpu) = NULL; + kthread_stop(p); + break; +#endif /* CONFIG_HOTPLUG_CPU */ + } + return NOTIFY_OK; +} + +static struct notifier_block __devinitdata cpu_nfb = { + .notifier_call = cpu_callback +}; + +__init void spawn_softlockup_task(void) +{ + void *cpu = (void *)(long)smp_processor_id(); + + cpu_callback(&cpu_nfb, CPU_UP_PREPARE, cpu); + cpu_callback(&cpu_nfb, CPU_ONLINE, cpu); + register_cpu_notifier(&cpu_nfb); + + notifier_chain_register(&panic_notifier_list, &panic_block); +} + |