On Wed, Mar 17, 2021 at 9:45 AM Ingo Molnar <mi...@kernel.org> wrote:
> * Ingo Molnar <mi...@kernel.org> wrote:
> > * Jiapeng Chong <jiapeng.ch...@linux.alibaba.com> wrote:
> >
> > > Fix the following coccicheck warnings:
> > >
> > > ./kernel/sched/core.c:8039:2-5: WARNING: Use BUG_ON instead of if
> > > condition followed by BUG.
> > >
> > > Reported-by: Abaci Robot <ab...@linux.alibaba.com>
> > > Signed-off-by: Jiapeng Chong <jiapeng.ch...@linux.alibaba.com>
> > > ---
> > > kernel/sched/core.c | 3 +--
> > > 1 file changed, 1 insertion(+), 2 deletions(-)
> > >
> > > diff --git a/kernel/sched/core.c b/kernel/sched/core.c
> > > index 9819121..7392bc0 100644
> > > --- a/kernel/sched/core.c
> > > +++ b/kernel/sched/core.c
> > > @@ -8035,8 +8035,7 @@ void __init sched_init_smp(void)
> > > mutex_unlock(&sched_domains_mutex);
> > >
> > > /* Move init over to a non-isolated CPU */
> > > - if (set_cpus_allowed_ptr(current,
> > > housekeeping_cpumask(HK_FLAG_DOMAIN)) < 0)
> > > - BUG();
> > > + BUG(set_cpus_allowed_ptr(current,
> > > housekeeping_cpumask(HK_FLAG_DOMAIN)) < 0);
> >
> > The patch doesn't quite do what the title & changelog claims...
>
> More importantly, we use this pattern when we don't want !CONFIG_BUG
> to remove the 'condition'.
>
> I.e. the "side effect" here is important scheduler logic. It must
> never be optimized out.
This behavior for !CONFIG_BUG has changed a while ago, it is now safe
to rely on the side-effect of the BUG_ON() condition regardless of
CONFIG_BUG. When that option is disabled, running into the condition
just ends up in a "do {} while (1)" loop.
Arnd
