Messages in this thread | | | From | Dexuan Cui <> | Subject | RE: for_each_cpu() is buggy for UP kernel? | Date | Tue, 15 May 2018 20:10:22 +0000 |
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> From: Linus Torvalds <torvalds@linux-foundation.org> > Sent: Tuesday, May 15, 2018 10:22 > To: Dexuan Cui <decui@microsoft.com> > > On Mon, May 14, 2018 at 8:02 PM Dexuan Cui <decui@microsoft.com> wrote: > > > If you're OK with the below fix (not tested yet), I'll submit a patch for it: > > > --- a/kernel/time/tick-broadcast.c > > +++ b/kernel/time/tick-broadcast.c > > @@ -616,6 +616,10 @@ static void tick_handle_oneshot_broadcast(struct > clock_event_device *dev) > > now = ktime_get(); > > /* Find all expired events */ > > for_each_cpu(cpu, tick_broadcast_oneshot_mask) { > > +#ifndef CONFIG_SMP > > + if (cpumask_empty(tick_broadcast_oneshot_mask)) > > + break; > > +#endif > > I'm certainly ok with this. It's hacky, but maybe being explicitly hacky is > good to "document" this gotcha. > > And I really do agree that this special UP case is nasty nasty and much too > subtle, and I hope that some day we won't care about UP at all, and maybe > kill it, or maybe just make for_each_cpu() generate the extra code to have > the actual same semantics as the SMP case. > > Linus
Thanks! I submitted the patch just now: https://lkml.org/lkml/2018/5/15/866
Thanks, -- Dexuan
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