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-rw-r--r--arch/x86/kernel/smpboot.c13
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();