sched: wakeup preempt when small overlap

[pandora-kernel.git] / kernel / softlockup.c

diff --git a/kernel/softlockup.c b/kernel/softlockup.c
index a272d78..cb838ee 100644 (file)
--- a/kernel/softlockup.c
+++ b/kernel/softlockup.c
@@ -13,6 +13,7 @@
 #include <linux/delay.h>
 #include <linux/freezer.h>
 #include <linux/kthread.h>
+#include <linux/lockdep.h>
 #include <linux/notifier.h>
 #include <linux/module.h>
 
@@ -25,7 +26,22 @@ static DEFINE_PER_CPU(unsigned long, print_timestamp);
 static DEFINE_PER_CPU(struct task_struct *, watchdog_task);
 
 static int __read_mostly did_panic;
-unsigned long __read_mostly softlockup_thresh = 60;
+int __read_mostly softlockup_thresh = 60;
+
+/*
+ * Should we panic (and reboot, if panic_timeout= is set) when a
+ * soft-lockup occurs:
+ */
+unsigned int __read_mostly softlockup_panic =
+                               CONFIG_BOOTPARAM_SOFTLOCKUP_PANIC_VALUE;
+
+static int __init softlockup_panic_setup(char *str)
+{
+       softlockup_panic = simple_strtoul(str, NULL, 0);
+
+       return 1;
+}
+__setup("softlockup_panic=", softlockup_panic_setup);
 
 static int
 softlock_panic(struct notifier_block *this, unsigned long event, void *ptr)
@@ -84,6 +100,14 @@ void softlockup_tick(void)
        struct pt_regs *regs = get_irq_regs();
        unsigned long now;
 
+       /* Is detection switched off? */
+       if (!per_cpu(watchdog_task, this_cpu) || softlockup_thresh <= 0) {
+               /* Be sure we don't false trigger if switched back on */
+               if (touch_timestamp)
+                       per_cpu(touch_timestamp, this_cpu) = 0;
+               return;
+       }
+
        if (touch_timestamp == 0) {
                __touch_softlockup_watchdog();
                return;
@@ -92,11 +116,8 @@ void softlockup_tick(void)
        print_timestamp = per_cpu(print_timestamp, this_cpu);
 
        /* report at most once a second */
-       if ((print_timestamp >= touch_timestamp &&
-                       print_timestamp < (touch_timestamp + 1)) ||
-                       did_panic || !per_cpu(watchdog_task, this_cpu)) {
+       if (print_timestamp == touch_timestamp || did_panic)
                return;
-       }
 
        /* do not print during early bootup: */
        if (unlikely(system_state != SYSTEM_RUNNING)) {
@@ -106,8 +127,11 @@ void softlockup_tick(void)
 
        now = get_timestamp(this_cpu);
 
-       /* Wake up the high-prio watchdog task every second: */
-       if (now > (touch_timestamp + 1))
+       /*
+        * Wake up the high-prio watchdog task twice per
+        * threshold timespan.
+        */
+       if (now > touch_timestamp + softlockup_thresh/2)
                wake_up_process(per_cpu(watchdog_task, this_cpu));
 
        /* Warn about unreasonable delays: */
@@ -121,11 +145,15 @@ void softlockup_tick(void)
                        this_cpu, now - touch_timestamp,
                        current->comm, task_pid_nr(current));
        print_modules();
+       print_irqtrace_events(current);
        if (regs)
                show_regs(regs);
        else
                dump_stack();
        spin_unlock(&print_lock);
+
+       if (softlockup_panic)
+               panic("softlockup: hung tasks");
 }
 
 /*
@@ -178,6 +206,9 @@ static void check_hung_task(struct task_struct *t, unsigned long now)
 
        t->last_switch_timestamp = now;
        touch_nmi_watchdog();
+
+       if (softlockup_panic)
+               panic("softlockup: blocked tasks");
 }
 
 /*
@@ -202,7 +233,8 @@ static void check_hung_uninterruptible_tasks(int this_cpu)
        do_each_thread(g, t) {
                if (!--max_count)
                        goto unlock;
-               if (t->state & TASK_UNINTERRUPTIBLE)
+               /* use "==" to skip the TASK_KILLABLE tasks waiting on NFS */
+               if (t->state == TASK_UNINTERRUPTIBLE)
                        check_hung_task(t, now);
        } while_each_thread(g, t);
  unlock:
@@ -307,14 +339,33 @@ static struct notifier_block __cpuinitdata cpu_nfb = {
        .notifier_call = cpu_callback
 };
 
-__init void spawn_softlockup_task(void)
+static int __initdata nosoftlockup;
+
+static int __init nosoftlockup_setup(char *str)
+{
+       nosoftlockup = 1;
+       return 1;
+}
+__setup("nosoftlockup", nosoftlockup_setup);
+
+static int __init spawn_softlockup_task(void)
 {
        void *cpu = (void *)(long)smp_processor_id();
-       int err = cpu_callback(&cpu_nfb, CPU_UP_PREPARE, cpu);
+       int err;
+
+       if (nosoftlockup)
+               return 0;
 
-       BUG_ON(err == NOTIFY_BAD);
+       err = cpu_callback(&cpu_nfb, CPU_UP_PREPARE, cpu);
+       if (err == NOTIFY_BAD) {
+               BUG();
+               return 1;
+       }
        cpu_callback(&cpu_nfb, CPU_ONLINE, cpu);
        register_cpu_notifier(&cpu_nfb);
 
        atomic_notifier_chain_register(&panic_notifier_list, &panic_block);
+
+       return 0;
 }
+early_initcall(spawn_softlockup_task);