Hi Dennis, > -----Original Message----- > From: Dennis Zhou [mailto:dennis@xxxxxxxxxx] > Sent: 2019年2月25日 23:14 > To: Peng Fan <peng.fan@xxxxxxx> > Cc: dennis@xxxxxxxxxx; tj@xxxxxxxxxx; cl@xxxxxxxxx; linux-mm@xxxxxxxxx; > linux-kernel@xxxxxxxxxxxxxxx; van.freenix@xxxxxxxxx > Subject: Re: [PATCH 1/2] percpu: km: remove SMP check > > On Sun, Feb 24, 2019 at 01:13:43PM +0000, Peng Fan wrote: > > percpu-km could only be selected by NEED_PER_CPU_KM which depends > on > > !SMP, so CONFIG_SMP will be false when choose percpu-km. > > > > Signed-off-by: Peng Fan <peng.fan@xxxxxxx> > > --- > > mm/percpu-km.c | 2 +- > > 1 file changed, 1 insertion(+), 1 deletion(-) > > > > diff --git a/mm/percpu-km.c b/mm/percpu-km.c index > > 0f643dc2dc65..66e5598be876 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_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. You might be wrong here. In mm/Kconfig, NEED_PER_CPU_KM default y depends on !SMP. So if CONFIG_SMP is not defined, NEED_PER_CPU_KM will be true. If we also define CONFIG_NEED_PER_CPU_PAGE_FIRST_CHUNK, the #error will have no chance to be detected because CONFIG_SMP already be false. That means CONFIG_SMP will always be false if percpu-km is used. So need to drop the CONFIG_SMP check here. Thanks, Peng. > > Thanks, > Dennis
