Merge branch 'core/softlockup-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip

* 'core/softlockup-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip:
  softlockup: fix invalid proc_handler for softlockup_panic
  softlockup: fix watchdog task wakeup frequency
  softlockup: fix watchdog task wakeup frequency
  softlockup: show irqtrace
  softlockup: print a module list on being stuck
  softlockup: fix NMI hangs due to lock race - 2.6.26-rc regression
  softlockup: fix false positives on nohz if CPU is 100% idle for more than 60 seconds
  softlockup: fix softlockup_thresh fix
  softlockup: fix softlockup_thresh unaligned access and disable detection at runtime
  softlockup: allow panic on lockup

6 files changed, 86 insertions, 15 deletions

diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt
index 30d44b78171a..47e7d8794fc6 100644
--- a/Documentation/kernel-parameters.txt
+++ b/Documentation/kernel-parameters.txt
@@ -2034,6 +2034,9 @@ and is between 256 and 4096 characters. It is defined in the file
 
         snd-ymfpci=     [HW,ALSA]
 
+        softlockup_panic=
+                        [KNL] Should the soft-lockup detector generate panics.
+
         sonypi.*=       [HW] Sony Programmable I/O Control Device driver
                         See Documentation/sonypi.txt
 
diff --git a/include/linux/sched.h b/include/linux/sched.h
index 1941d8b5cf11..af443a08431f 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -295,10 +295,11 @@ extern void softlockup_tick(void);
 extern void spawn_softlockup_task(void);
 extern void touch_softlockup_watchdog(void);
 extern void touch_all_softlockup_watchdogs(void);
-extern unsigned long  softlockup_thresh;
+extern unsigned int  softlockup_panic;
 extern unsigned long sysctl_hung_task_check_count;
 extern unsigned long sysctl_hung_task_timeout_secs;
 extern unsigned long sysctl_hung_task_warnings;
+extern int softlockup_thresh;
 #else
 static inline void softlockup_tick(void)
 {
diff --git a/kernel/softlockup.c b/kernel/softlockup.c
index a272d78185eb..7bd8d1aadd5d 100644
--- 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");
 }
 
 /*
diff --git a/kernel/sysctl.c b/kernel/sysctl.c
index b859e6b5a767..2a7b9d88706b 100644
--- a/kernel/sysctl.c
+++ b/kernel/sysctl.c
@@ -88,12 +88,13 @@ extern int rcutorture_runnable;
 #endif /* #ifdef CONFIG_RCU_TORTURE_TEST */
 
 /* Constants used for minimum and  maximum */
-#if defined(CONFIG_DETECT_SOFTLOCKUP) || defined(CONFIG_HIGHMEM)
+#if defined(CONFIG_HIGHMEM) || defined(CONFIG_DETECT_SOFTLOCKUP)
 static int one = 1;
 #endif
 
 #ifdef CONFIG_DETECT_SOFTLOCKUP
 static int sixty = 60;
+static int neg_one = -1;
 #endif
 
 #ifdef CONFIG_MMU
@@ -739,13 +740,24 @@ static struct ctl_table kern_table[] = {
 #ifdef CONFIG_DETECT_SOFTLOCKUP
         {
                 .ctl_name       = CTL_UNNUMBERED,
+                .procname       = "softlockup_panic",
+                .data           = &softlockup_panic,
+                .maxlen         = sizeof(int),
+                .mode           = 0644,
+                .proc_handler   = &proc_dointvec_minmax,
+                .strategy       = &sysctl_intvec,
+                .extra1         = &zero,
+                .extra2         = &one,
+        },
+        {
+                .ctl_name       = CTL_UNNUMBERED,
                 .procname       = "softlockup_thresh",
                 .data           = &softlockup_thresh,
-                .maxlen         = sizeof(unsigned long),
+                .maxlen         = sizeof(int),
                 .mode           = 0644,
-                .proc_handler   = &proc_doulongvec_minmax,
+                .proc_handler   = &proc_dointvec_minmax,
                 .strategy       = &sysctl_intvec,
-                .extra1         = &one,
+                .extra1         = &neg_one,
                 .extra2         = &sixty,
         },
         {
diff --git a/kernel/time/tick-sched.c b/kernel/time/tick-sched.c
index beef7ccdf842..942fc7c85283 100644
--- a/kernel/time/tick-sched.c
+++ b/kernel/time/tick-sched.c
@@ -140,8 +140,6 @@ void tick_nohz_update_jiffies(void)
         if (!ts->tick_stopped)
                 return;
 
-        touch_softlockup_watchdog();
-
         cpu_clear(cpu, nohz_cpu_mask);
         now = ktime_get();
         ts->idle_waketime = now;
@@ -149,6 +147,8 @@ void tick_nohz_update_jiffies(void)
         local_irq_save(flags);
         tick_do_update_jiffies64(now);
         local_irq_restore(flags);
+
+        touch_softlockup_watchdog();
 }
 
 void tick_nohz_stop_idle(int cpu)
diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
index ba106db5a65b..882c51048993 100644
--- a/lib/Kconfig.debug
+++ b/lib/Kconfig.debug
@@ -150,7 +150,7 @@ config DETECT_SOFTLOCKUP
         help
           Say Y here to enable the kernel to detect "soft lockups",
           which are bugs that cause the kernel to loop in kernel
-          mode for more than 10 seconds, without giving other tasks a
+          mode for more than 60 seconds, without giving other tasks a
           chance to run.
 
           When a soft-lockup is detected, the kernel will print the
@@ -162,6 +162,30 @@ config DETECT_SOFTLOCKUP
            can be detected via the NMI-watchdog, on platforms that
            support it.)
 
+config BOOTPARAM_SOFTLOCKUP_PANIC
+        bool "Panic (Reboot) On Soft Lockups"
+        depends on DETECT_SOFTLOCKUP
+        help
+          Say Y here to enable the kernel to panic on "soft lockups",
+          which are bugs that cause the kernel to loop in kernel
+          mode for more than 60 seconds, without giving other tasks a
+          chance to run.
+
+          The panic can be used in combination with panic_timeout,
+          to cause the system to reboot automatically after a
+          lockup has been detected. This feature is useful for
+          high-availability systems that have uptime guarantees and
+          where a lockup must be resolved ASAP.
+
+          Say N if unsure.
+
+config BOOTPARAM_SOFTLOCKUP_PANIC_VALUE
+        int
+        depends on DETECT_SOFTLOCKUP
+        range 0 1
+        default 0 if !BOOTPARAM_SOFTLOCKUP_PANIC
+        default 1 if BOOTPARAM_SOFTLOCKUP_PANIC
+
 config SCHED_DEBUG
         bool "Collect scheduler debugging info"
         depends on DEBUG_KERNEL && PROC_FS