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Subject[PATCH] disable softlockup detection at boottime
This patch allows softlockup detection to be disabled by specifying
a boottime parameter.

Signed-off-by: Dimitri Sivanich <sivanich@sgi.com>

Index: linux/kernel/softlockup.c
===================================================================
--- linux.orig/kernel/softlockup.c 2008-04-23 13:50:06.000000000 -0500
+++ linux/kernel/softlockup.c 2008-04-23 14:39:36.267398531 -0500
@@ -24,6 +24,7 @@ static DEFINE_PER_CPU(unsigned long, tou
static DEFINE_PER_CPU(unsigned long, print_timestamp);
static DEFINE_PER_CPU(struct task_struct *, watchdog_task);

+static int __read_mostly softlockup_off;
static int __read_mostly did_panic;
unsigned long __read_mostly softlockup_thresh = 60;

@@ -53,7 +54,8 @@ void touch_softlockup_watchdog(void)
{
int this_cpu = raw_smp_processor_id();

- __raw_get_cpu_var(touch_timestamp) = get_timestamp(this_cpu);
+ if (!softlockup_off)
+ __raw_get_cpu_var(touch_timestamp) = get_timestamp(this_cpu);
}
EXPORT_SYMBOL(touch_softlockup_watchdog);

@@ -61,6 +63,9 @@ void touch_all_softlockup_watchdogs(void
{
int cpu;

+ if (softlockup_off)
+ return;
+
/* Cause each CPU to re-update its timestamp rather than complain */
for_each_online_cpu(cpu)
per_cpu(touch_timestamp, cpu) = 0;
@@ -79,6 +84,9 @@ void softlockup_tick(void)
struct pt_regs *regs = get_irq_regs();
unsigned long now;

+ if (softlockup_off)
+ return;
+
if (touch_timestamp == 0) {
touch_softlockup_watchdog();
return;
@@ -306,9 +314,19 @@ __init void spawn_softlockup_task(void)
void *cpu = (void *)(long)smp_processor_id();
int err = cpu_callback(&cpu_nfb, CPU_UP_PREPARE, cpu);

+ if (softlockup_off)
+ return;
+
BUG_ON(err == NOTIFY_BAD);
cpu_callback(&cpu_nfb, CPU_ONLINE, cpu);
register_cpu_notifier(&cpu_nfb);

atomic_notifier_chain_register(&panic_notifier_list, &panic_block);
}
+
+static int __init disable_softlockup_detection(char *str)
+{
+ softlockup_off = 1;
+ return 1;
+}
+__setup("nosoftlockup", disable_softlockup_detection);

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