[PATCH] Ignore bogus ACPI info for offline CPUs

Thomas Gleixner
2007-05-19T14:17:17Z

Booting a SMP kernel with maxcpus=1 on a SMP system leads to a hard
hang, because ACPI ignores the maxcpus setting and sends timer broadcast
info for the offline CPUs. This results in a stuck for ever call to
smp_call_function_single() on an offline CPU.

Ignore the bogus information and print a kernel error to remind ACPI
folks to fix it.

Affects 2.6.21 / 2.6.22-rc

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

Index: linux-2.6.22-rc/kernel/time/tick-broadcast.c
===================================================================
--- linux-2.6.22-rc.orig/kernel/time/tick-broadcast.c
+++ linux-2.6.22-rc/kernel/time/tick-broadcast.c
@@ -244,11 +244,18 @@ void tick_broadcast_on_off(unsigned long
{
int cpu = get_cpu();

- if (cpu == *oncpu)
- tick_do_broadcast_on_off(&reason);
- else
- smp_call_function_single(*oncpu, tick_do_broadcast_on_off,
- &reason, 1, 1);
+ if (!cpu_isset(*oncpu, cpu_online_map)) {
+ printk(KERN_ERR "tick-braodcast: ignoring broadcast for "
+ "offline CPU #%d\n", *oncpu);
+ } else {
+
+ if (cpu == *oncpu)
+ tick_do_broadcast_on_off(&reason);
+ else
+ smp_call_function_single(*oncpu,
+ tick_do_broadcast_on_off,
+ &reason, 1, 1);
+ }
put_cpu();
}