[RFC rcu/next] torture: Stop onoff task if there is only one cpu

Boqun Feng
2016-05-02T02:27:11Z

If the whole system has only one cpu, that cpu won't be able to be
offlined, so there is no need onoff task is stil running.

Signed-off-by: Boqun Feng <boqun.feng@gmail.com>
---

I hit something like the following while I was running rcutorture
in a guest with only one vCPU:

[ 31.197457] rcu-torture:torture_onoff task: offlining 0
[ 31.197508] rcu-torture:torture_onoff task: offline 0 failed: errno -16

I know this is an expected behavior, but think we could just stop
the onoff task if there is only one cpu.

kernel/torture.c | 8 ++++++++
1 file changed, 8 insertions(+)

diff --git a/kernel/torture.c b/kernel/torture.c
index fb39a06bbef5..a85b7d61d9dd 100644
--- a/kernel/torture.c
+++ b/kernel/torture.c
@@ -194,6 +194,12 @@ torture_onoff(void *arg)
for_each_online_cpu(cpu)
maxcpu = cpu;
WARN_ON(maxcpu < 0);
+
+ if (maxcpu == 0) {
+ VERBOSE_TOROUT_STRING("only one cpu is found, onoff is impossible");
+ goto stop;
+ }
+
if (onoff_holdoff > 0) {
VERBOSE_TOROUT_STRING("torture_onoff begin holdoff");
schedule_timeout_interruptible(onoff_holdoff);
@@ -209,6 +215,8 @@ torture_onoff(void *arg)
&sum_online, &min_online, &max_online);
schedule_timeout_interruptible(onoff_interval);
}
+
+stop:
torture_kthread_stopping("torture_onoff");
return 0;
}
--
2.8.0