On Mon, May 02, 2016 at 10:30:00AM +0800, Boqun Feng wrote: > 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 <[email protected]> > --- > > 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.
I find it a little bit unfortunate that this kicks off a thread just to immediately exit that thread, rather than never starting it in the first place. However, it also seems like the most convenient solution here, and I don't see much point in going out of the way to optimize this test for uniprocessor systems. Reviewed-by: Josh Triplett <[email protected]> > 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 >
