On Tue, Feb 26, 2019 at 03:16:44PM +0000, Christopher Lameter wrote: > On Mon, 25 Feb 2019, Dennis Zhou wrote: > > > > @@ -27,7 +27,7 @@ > > > * chunk size is not aligned. percpu-km code will whine about it. > > > */ > > > > > > -#if defined(CONFIG_SMP) && defined(CONFIG_NEED_PER_CPU_PAGE_FIRST_CHUNK) > > > +#if defined(CONFIG_NEED_PER_CPU_PAGE_FIRST_CHUNK) > > > #error "contiguous percpu allocation is incompatible with paged first chunk" > > > #endif > > > > > > -- > > > 2.16.4 > > > > > > > Hi, > > > > I think keeping CONFIG_SMP makes this easier to remember dependencies > > rather than having to dig into the config. So this is a NACK from me. > > But it simplifies the code and makes it easier to read. > > I think the check isn't quite right after looking at it a little longer. Looking at x86, I believe you can compile it with !SMP and CONFIG_NEED_PER_CPU_PAGE_FIRST_CHUNK will still be set. This should still work because x86 has an MMU. I think more correctly it would be something like below, but I don't have the time to fully verify it right now. Thanks, Dennis --- diff --git a/mm/percpu-km.c b/mm/percpu-km.c index 0f643dc2dc65..69ccad7d9807 100644 --- a/mm/percpu-km.c +++ b/mm/percpu-km.c @@ -27,7 +27,7 @@ * chunk size is not aligned. percpu-km code will whine about it. */ -#if defined(CONFIG_SMP) && defined(CONFIG_NEED_PER_CPU_PAGE_FIRST_CHUNK) +#if !defined(CONFIG_MMU) && defined(CONFIG_NEED_PER_CPU_PAGE_FIRST_CHUNK) #error "contiguous percpu allocation is incompatible with paged first chunk" #endif
