>
> On Thu, Aug 24, 2023 at 04:42:06PM +0800, Zqiang wrote:
> > Currently, the maxcpu is set by traversing online CPUs, however, if
> > the rcutorture.onoff_holdoff is set zero and onoff_interval is set
> > non-zero, and the some CPUs with larger cpuid has been offline before
> > setting maxcpu, for these CPUs, even if they are online again, also
> > cannot be offload or deoffload.
> >
> > This commit therefore use for_each_possible_cpu() instead of
> > for_each_online_cpu() in rcu_nocb_toggle().
> >
> > Signed-off-by: Zqiang <qiang.zhang1211@xxxxxxxxx>
> > ---
> > kernel/rcu/rcutorture.c | 2 +-
> > 1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/kernel/rcu/rcutorture.c b/kernel/rcu/rcutorture.c
> > index a58372bdf0c1..b75d0fe558ce 100644
> > --- a/kernel/rcu/rcutorture.c
> > +++ b/kernel/rcu/rcutorture.c
> > @@ -2131,7 +2131,7 @@ static int rcu_nocb_toggle(void *arg)
> > VERBOSE_TOROUT_STRING("rcu_nocb_toggle task started");
> > while (!rcu_inkernel_boot_has_ended())
> > schedule_timeout_interruptible(HZ / 10);
> > - for_each_online_cpu(cpu)
> > + for_each_possible_cpu(cpu)
>
> Last I checked, bad things could happen if the code attempted to
> nocb_toggle a CPU that had not yet come online. Has that changed?
For example, there are 8 online CPUs in the system, before we traversing online
CPUs and set maxcpu, CPU7 has been offline, this causes us to miss nocb_toggle
for CPU7(maxcpu=6)
Even though we still use for_each_online_cpu(), the things described
above also happen. before we toggle the CPU, this CPU has been offline.
Thanks
Zqiang
>
> Thanx, Paul
>
> > maxcpu = cpu;
> > WARN_ON(maxcpu < 0);
> > if (toggle_interval > ULONG_MAX)
> > --
> > 2.17.1
> >
