1 files changed, 13 insertions, 0 deletions

diff --git a/arch/x86/kernel/smpboot.c b/arch/x86/kernel/smpboot.c
index 33a0c11797de..9fd3137230d4 100644
--- a/arch/x86/kernel/smpboot.c
+++ b/arch/x86/kernel/smpboot.c
@@ -285,6 +285,19 @@ notrace static void __cpuinit start_secondary(void *unused)
         per_cpu(cpu_state, smp_processor_id()) = CPU_ONLINE;
         x86_platform.nmi_init();
 
+        /*
+         * Wait until the cpu which brought this one up marked it
+         * online before enabling interrupts. If we don't do that then
+         * we can end up waking up the softirq thread before this cpu
+         * reached the active state, which makes the scheduler unhappy
+         * and schedule the softirq thread on the wrong cpu. This is
+         * only observable with forced threaded interrupts, but in
+         * theory it could also happen w/o them. It's just way harder
+         * to achieve.
+         */
+        while (!cpumask_test_cpu(smp_processor_id(), cpu_active_mask))
+                cpu_relax();
+
         /* enable local interrupts */
         local_irq_enable();