Update cpu shutdown code to ack the local APIC EOI register before

invoking sti/hlt. This is needed to get hot-plugged CPUs to re-online
in Pisces/Linux on some architectures

arch/x86_64/kernel/cpu.c

@@ -9,6 +9,7 @@
 #include <lwk/aspace.h>
 #include <lwk/xcall.h>
 #include <lwk/cpuinfo.h>
+#include <lwk/interrupt.h>
 
 #include <arch/processor.h>
 #include <arch/desc.h>
@@ -453,6 +454,17 @@ phys_cpu_remove(unsigned int phys_cpu_id,
 void
 arch_shutdown_cpu(void)
 {
-    local_irq_disable();
-    halt();
+	/* The LAPIC can end up in a weird state if we go into sti/hlt without
+	 * acking the EOI first. Of course, this is only the case if we are in
+	 * interrupt
+	 */
+	if (in_interrupt())
+		lapic_ack_interrupt();
+
+	local_irq_disable();
+
+	while (1) {
+	    halt();
+	    cpu_relax();
+	}
 }

kernel/cpu.c

@@ -1,13 +1,14 @@
 #include <lwk/kernel.h>
 #include <lwk/xcall.h>
+#include <lwk/smp.h>
 
 
 extern void arch_shutdown_cpu(void);
 
 static void
 shutdown_cpu(void * info)
 {
-    arch_shutdown_cpu();
+	arch_shutdown_cpu();
 }
 
 /*
@@ -16,5 +17,6 @@ shutdown_cpu(void * info)
 void
 shutdown_cpus(void)
 {
-    xcall_function(cpu_online_map, shutdown_cpu, NULL, 0);
+	printk("CPU #%u: shutting down all CPUs\n", this_cpu);
+	on_each_cpu(shutdown_cpu, NULL, 0);
 }