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8446f1d391
This patch adds a new kernel debug feature: CONFIG_DETECT_SOFTLOCKUP. When enabled then per-CPU watchdog threads are started, which try to run once per second. If they get delayed for more than 10 seconds then a callback from the timer interrupt detects this condition and prints out a warning message and a stack dump (once per lockup incident). The feature is otherwise non-intrusive, it doesnt try to unlock the box in any way, it only gets the debug info out, automatically, and on all CPUs affected by the lockup. Signed-off-by: Ingo Molnar <mingo@elte.hu> Signed-off-by: Nishanth Aravamudan <nacc@us.ibm.com> Signed-Off-By: Matthias Urlichs <smurf@smurf.noris.de> Signed-off-by: Richard Purdie <rpurdie@rpsys.net> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
152 lines
3.6 KiB
C
152 lines
3.6 KiB
C
/*
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* Detect Soft Lockups
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*
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* started by Ingo Molnar, (C) 2005, Red Hat
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*
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* this code detects soft lockups: incidents in where on a CPU
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* the kernel does not reschedule for 10 seconds or more.
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*/
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#include <linux/mm.h>
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#include <linux/cpu.h>
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#include <linux/init.h>
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#include <linux/delay.h>
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#include <linux/kthread.h>
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#include <linux/notifier.h>
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#include <linux/module.h>
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static DEFINE_SPINLOCK(print_lock);
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static DEFINE_PER_CPU(unsigned long, timestamp) = 0;
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static DEFINE_PER_CPU(unsigned long, print_timestamp) = 0;
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static DEFINE_PER_CPU(struct task_struct *, watchdog_task);
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static int did_panic = 0;
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static int softlock_panic(struct notifier_block *this, unsigned long event,
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void *ptr)
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{
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did_panic = 1;
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return NOTIFY_DONE;
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}
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static struct notifier_block panic_block = {
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.notifier_call = softlock_panic,
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};
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void touch_softlockup_watchdog(void)
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{
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per_cpu(timestamp, raw_smp_processor_id()) = jiffies;
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}
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EXPORT_SYMBOL(touch_softlockup_watchdog);
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/*
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* This callback runs from the timer interrupt, and checks
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* whether the watchdog thread has hung or not:
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*/
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void softlockup_tick(struct pt_regs *regs)
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{
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int this_cpu = smp_processor_id();
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unsigned long timestamp = per_cpu(timestamp, this_cpu);
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if (per_cpu(print_timestamp, this_cpu) == timestamp)
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return;
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/* Do not cause a second panic when there already was one */
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if (did_panic)
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return;
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if (time_after(jiffies, timestamp + 10*HZ)) {
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per_cpu(print_timestamp, this_cpu) = timestamp;
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spin_lock(&print_lock);
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printk(KERN_ERR "BUG: soft lockup detected on CPU#%d!\n",
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this_cpu);
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show_regs(regs);
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spin_unlock(&print_lock);
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}
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}
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/*
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* The watchdog thread - runs every second and touches the timestamp.
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*/
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static int watchdog(void * __bind_cpu)
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{
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struct sched_param param = { .sched_priority = 99 };
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int this_cpu = (long) __bind_cpu;
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printk("softlockup thread %d started up.\n", this_cpu);
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sched_setscheduler(current, SCHED_FIFO, ¶m);
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current->flags |= PF_NOFREEZE;
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set_current_state(TASK_INTERRUPTIBLE);
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/*
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* Run briefly once per second - if this gets delayed for
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* more than 10 seconds then the debug-printout triggers
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* in softlockup_tick():
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*/
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while (!kthread_should_stop()) {
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msleep_interruptible(1000);
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touch_softlockup_watchdog();
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}
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__set_current_state(TASK_RUNNING);
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return 0;
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}
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/*
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* Create/destroy watchdog threads as CPUs come and go:
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*/
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static int __devinit
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cpu_callback(struct notifier_block *nfb, unsigned long action, void *hcpu)
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{
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int hotcpu = (unsigned long)hcpu;
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struct task_struct *p;
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switch (action) {
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case CPU_UP_PREPARE:
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BUG_ON(per_cpu(watchdog_task, hotcpu));
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p = kthread_create(watchdog, hcpu, "watchdog/%d", hotcpu);
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if (IS_ERR(p)) {
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printk("watchdog for %i failed\n", hotcpu);
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return NOTIFY_BAD;
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}
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per_cpu(watchdog_task, hotcpu) = p;
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kthread_bind(p, hotcpu);
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break;
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case CPU_ONLINE:
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wake_up_process(per_cpu(watchdog_task, hotcpu));
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break;
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#ifdef CONFIG_HOTPLUG_CPU
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case CPU_UP_CANCELED:
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/* Unbind so it can run. Fall thru. */
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kthread_bind(per_cpu(watchdog_task, hotcpu), smp_processor_id());
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case CPU_DEAD:
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p = per_cpu(watchdog_task, hotcpu);
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per_cpu(watchdog_task, hotcpu) = NULL;
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kthread_stop(p);
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break;
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#endif /* CONFIG_HOTPLUG_CPU */
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}
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return NOTIFY_OK;
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}
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static struct notifier_block __devinitdata cpu_nfb = {
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.notifier_call = cpu_callback
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};
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__init void spawn_softlockup_task(void)
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{
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void *cpu = (void *)(long)smp_processor_id();
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cpu_callback(&cpu_nfb, CPU_UP_PREPARE, cpu);
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cpu_callback(&cpu_nfb, CPU_ONLINE, cpu);
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register_cpu_notifier(&cpu_nfb);
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notifier_chain_register(&panic_notifier_list, &panic_block);
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}
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