softlockup: add a /proc tuning parameter

Control the trigger limit for softlockup warnings.  This is useful for
debugging softlockups, by lowering the softlockup_thresh to identify
possible softlockups earlier.

This patch:
1. Adds a sysctl softlockup_thresh with valid values of 1-60s
   (Higher value to disable false positives)
2. Changes the softlockup printk to print the cpu softlockup time

[akpm@linux-foundation.org: Fix various warnings and add definition of "two"]
Signed-off-by: Ravikiran Thirumalai <kiran@scalex86.org>
Signed-off-by: Shai Fultheim <shai@scalex86.org>
Acked-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 5 insertions, 2 deletions

diff --git a/kernel/softlockup.c b/kernel/softlockup.c
index 72c2561ff5f..edeeef3a6a3 100644
--- a/kernel/softlockup.c
+++ b/kernel/softlockup.c
@@ -24,6 +24,7 @@ static DEFINE_PER_CPU(unsigned long, print_timestamp);
 static DEFINE_PER_CPU(struct task_struct *, watchdog_task);
 
 static int did_panic;
+int softlockup_thresh = 10;
 
 static int
 softlock_panic(struct notifier_block *this, unsigned long event, void *ptr)
@@ -104,13 +105,15 @@ void softlockup_tick(void)
                 wake_up_process(per_cpu(watchdog_task, this_cpu));
 
         /* Warn about unreasonable 10+ seconds delays: */
-        if (now <= (touch_timestamp + 10))
+        if (now <= (touch_timestamp + softlockup_thresh))
                 return;
 
         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);
+        printk(KERN_ERR "BUG: soft lockup - CPU#%d stuck for %lus! [%s:%d]\n",
+                        this_cpu, now - touch_timestamp,
+                                current->comm, current->pid);
         if (regs)
                 show_regs(regs);
         else