Ignore bogus ACPI info for offline CPUs

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.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: <stable@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 12 insertions, 5 deletions

diff --git a/kernel/time/tick-broadcast.c b/kernel/time/tick-broadcast.c
index eadfce2fff74..8001d37071f5 100644
--- a/kernel/time/tick-broadcast.c
+++ b/kernel/time/tick-broadcast.c
@@ -243,11 +243,18 @@ void tick_broadcast_on_off(unsigned long reason, int *oncpu)
 {
         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();
 }