ARM: smp: implement arch_trigger_all_cpus_backtrace using IPI

Based on a rough patch by frank.rowand@am.sony.com

Since ARM doesn't have an NMI (fiq's are not always available),
send an IPI to all other CPUs (current cpu prints the stack directly)
to capture a backtrace.

Change-Id: I8b163c8cec05d521b433ae133795865e8a33d4e2
Signed-off-by: Dima Zavin <dima@android.com>
diff --git a/arch/arm/kernel/process.c b/arch/arm/kernel/process.c
index 34fca2e..6810cc1 100644
--- a/arch/arm/kernel/process.c
+++ b/arch/arm/kernel/process.c
@@ -62,6 +62,18 @@
 
 #include <mach/system.h>
 
+#ifdef CONFIG_SMP
+void arch_trigger_all_cpu_backtrace(void)
+{
+	smp_send_all_cpu_backtrace();
+}
+#else
+void arch_trigger_all_cpu_backtrace(void)
+{
+	dump_stack();
+}
+#endif
+
 void disable_hlt(void)
 {
 	hlt_counter++;