This commit was manufactured by cvs2svn to create branch 'vserver'.

[linux-2.6.git] / kernel / softlockup.c

diff --git a/kernel/softlockup.c b/kernel/softlockup.c
new file mode 100644 (file)
index 0000000..14c7faf
--- /dev/null
+++ b/kernel/softlockup.c
@@ -0,0 +1,156 @@
+/*
+ * Detect Soft Lockups
+ *
+ * started by Ingo Molnar, Copyright (C) 2005, 2006 Red Hat, Inc.
+ *
+ * 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, touch_timestamp);
+static DEFINE_PER_CPU(unsigned long, print_timestamp);
+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(touch_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(void)
+{
+       int this_cpu = smp_processor_id();
+       unsigned long touch_timestamp = per_cpu(touch_timestamp, this_cpu);
+
+       /* prevent double reports: */
+       if (per_cpu(print_timestamp, this_cpu) == touch_timestamp ||
+               did_panic ||
+                       !per_cpu(watchdog_task, this_cpu))
+               return;
+
+       /* do not print during early bootup: */
+       if (unlikely(system_state != SYSTEM_RUNNING)) {
+               touch_softlockup_watchdog();
+               return;
+       }
+
+       /* Wake up the high-prio watchdog task every second: */
+       if (time_after(jiffies, touch_timestamp + HZ))
+               wake_up_process(per_cpu(watchdog_task, this_cpu));
+
+       /* Warn about unreasonable 10+ seconds delays: */
+       if (time_after(jiffies, touch_timestamp + 10*HZ)) {
+               per_cpu(print_timestamp, this_cpu) = touch_timestamp;
+
+               spin_lock(&print_lock);
+               printk(KERN_ERR "BUG: soft lockup detected on CPU#%d!\n",
+                       this_cpu);
+               dump_stack();
+               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 };
+
+       sched_setscheduler(current, SCHED_FIFO, &param);
+       current->flags |= PF_NOFREEZE;
+
+       /*
+        * Run briefly once per second to reset the softlockup timestamp.
+        * If this gets delayed for more than 10 seconds then the
+        * debug-printout triggers in softlockup_tick().
+        */
+       while (!kthread_should_stop()) {
+               set_current_state(TASK_INTERRUPTIBLE);
+               touch_softlockup_watchdog();
+               schedule();
+       }
+
+       return 0;
+}
+
+/*
+ * Create/destroy watchdog threads as CPUs come and go:
+ */
+static int
+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(touch_timestamp, hotcpu) = jiffies;
+               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),
+                            any_online_cpu(cpu_online_map));
+       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 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);
+
+       atomic_notifier_chain_register(&panic_notifier_list, &panic_block);
+}