On Tue, 17 May 2011 03:03:29 +0200, Jean-Christophe PLAGNIOL-VILLARD said: > On 15:38 Mon 16 May , Arnaud Lacombe wrote: > > On Mon, May 16, 2011 at 3:03 PM, <Valdis.Kletnieks@xxxxxx> wrote: > > > #if defined(CONFIG_NO_HZ) && defined(CONFIG_SMP) > > > if (!pinned && get_sysctl_timer_migration() && idle_cpu(cpu)) > > > cpu = get_nohz_timer_target(); > > > #endif > > > new_base = per_cpu(tvec_bases, cpu); > > I already exposed this case, but let's prove it: > > > > % grep CONFIG_SMP .config > > # CONFIG_SMP is not set > > > > % git diff > > diff --git a/kernel/timer.c b/kernel/timer.c > > index fd61986..ea4a5ba 100644 > > --- a/kernel/timer.c > > +++ b/kernel/timer.c > > @@ -681,10 +681,8 @@ __mod_timer(struct timer_list *timer, unsigned > > long expires, > > > > cpu = smp_processor_id(); > > > > -#if defined(CONFIG_NO_HZ) && defined(CONFIG_SMP) > > - if (!pinned && get_sysctl_timer_migration() && idle_cpu(cpu)) > > + if (0 && 0 && !pinned && get_sysctl_timer_migration() && idle_cpu(cpu)) > > cpu = get_nohz_timer_target(); > > -#endif > > new_base = per_cpu(tvec_bases, cpu); > > > > % gmake kernel/timer.o > > CHK include/linux/version.h > > CHK include/generated/utsrelease.h > > CALL scripts/checksyscalls.sh > > CC kernel/timer.o > > kernel/timer.c: In function '__mod_timer': > > kernel/timer.c:685:3: error: implicit declaration of function > > 'get_nohz_timer_target' > > gmake[1]: *** [kernel/timer.o] Error 1 > > gmake: *** [kernel/timer.o] Error 2 > because we do not define the inline function if the CONFIG_ is not define > as we are supposed to do if we want to compile without ifdef everywhere Right - the point is that since many/most cases of #ifdef CONFIG_FOO in open code won't compile cleanly if converted to config_is_foo(), it limits the usefulness of the feature. Which raises another question - does this create a maintenance headache, where people who used to just 'grep -r CONFIG_FOO' to find code they needed to fix up now have to remember to do a *second* grep to find all callsites?
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