kernel/cpu.c: create a CPU_STARTING cpu_chain notifier

Right now, there is no notifier that is called on a new cpu, before the new
cpu begins processing interrupts/softirqs.
Various kernel function would need that notification, e.g. kvm works around
by calling smp_call_function_single(), rcu polls cpu_online_map.

The patch adds a CPU_STARTING notification. It also adds a helper function
that sends the message to all cpu_chain handlers.

Tested on x86-64.
All other archs are untested. Especially on sparc, I'm not sure if I got
it right.

Signed-off-by: Manfred Spraul <manfred@colorfullife.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

1 files changed, 3 insertions, 0 deletions

diff --git a/arch/alpha/kernel/smp.c b/arch/alpha/kernel/smp.c
index 83df541650fc..06b6fdab639f 100644
--- a/arch/alpha/kernel/smp.c
+++ b/arch/alpha/kernel/smp.c
@@ -149,6 +149,9 @@ smp_callin(void)
         atomic_inc(&init_mm.mm_count);
         current->active_mm = &init_mm;
 
+        /* inform the notifiers about the new cpu */
+        notify_cpu_starting(cpuid);
+
         /* Must have completely accurate bogos.  */
         local_irq_enable();