s390/smp: wait until secondaries are active & online

This is the s390 version of 875ebe940d77 ("powerpc/smp: Wait until secondaries
are active & online").
The race described in length within the commit message is also possible on s390
and every other architecture. So fix this race on s390 as well.

Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>

1 files changed, 2 insertions, 1 deletions

diff --git a/arch/s390/kernel/smp.c b/arch/s390/kernel/smp.c
index d140160c9aec..efd2c1968000 100644
--- a/arch/s390/kernel/smp.c
+++ b/arch/s390/kernel/smp.c
@@ -818,7 +818,8 @@ int __cpu_up(unsigned int cpu, struct task_struct *tidle)
         pcpu_prepare_secondary(pcpu, cpu);
         pcpu_attach_task(pcpu, tidle);
         pcpu_start_fn(pcpu, smp_start_secondary, NULL);
-        while (!cpu_online(cpu))
+        /* Wait until cpu puts itself in the online & active maps */
+        while (!cpu_online(cpu) || !cpu_active(cpu))
                 cpu_relax();
         return 0;
 }