Re: [PATCH V3 -next] powerpc: kernel/time.c - cleanup warnings

[Christophe Leroy]

Le 24/03/2021 à 10:29, Alexandre Belloni a écrit :
> On 24/03/2021 05:09:39-0400, He Ying wrote:
> > We found these warnings in arch/powerpc/kernel/time.c as follows:
> > warning: symbol 'decrementer_max' was not declared. Should it be static?
> > warning: symbol 'rtc_lock' was not declared. Should it be static?
> > warning: symbol 'dtl_consumer' was not declared. Should it be static?
> >
> > Declare 'decrementer_max' in powerpc asm/time.h.
> > Include linux/mc146818rtc.h in powerpc kernel/time.c where 'rtc_lock'
> > is declared. And remove duplicated declaration of 'rtc_lock' in powerpc
> > platforms/chrp/time.c because it has included linux/mc146818rtc.h.
> > Move 'dtl_consumer' definition behind "include <asm/dtl.h>" because it
> > is declared there.
> >
> > Reported-by: Hulk Robot <hulkci@xxxxxxxxxx>
> > Signed-off-by: He Ying <heying24@xxxxxxxxxx>
> > ---
> > V2:
> > - Instead of including linux/mc146818rtc.h in powerpc kernel/time.c, declare
> >    rtc_lock in powerpc asm/time.h.
> > V3:
> > - Recover to V1, that is including linux/mc146818rtc.h in powerpc
> >    kernel/time.c. And remove duplicated declaration of 'rtc_lock' in powerpc
> >    platforms/chrp/time.c because it has included linux/mc146818rtc.h.
> >
> >   arch/powerpc/include/asm/time.h    | 1 +
> >   arch/powerpc/kernel/time.c         | 9 ++++-----
> >   arch/powerpc/platforms/chrp/time.c | 2 --
> >   3 files changed, 5 insertions(+), 7 deletions(-)
> >
> > diff --git a/arch/powerpc/include/asm/time.h b/arch/powerpc/include/asm/time.h
> > index 8dd3cdb25338..2cd2b50bedda 100644
> > --- a/arch/powerpc/include/asm/time.h
> > +++ b/arch/powerpc/include/asm/time.h
> > @@ -22,6 +22,7 @@ extern unsigned long tb_ticks_per_jiffy;
> >   extern unsigned long tb_ticks_per_usec;
> >   extern unsigned long tb_ticks_per_sec;
> >   extern struct clock_event_device decrementer_clockevent;
> > +extern u64 decrementer_max;
> >   
> >   
> >   extern void generic_calibrate_decr(void);
> > diff --git a/arch/powerpc/kernel/time.c b/arch/powerpc/kernel/time.c
> > index b67d93a609a2..ac81f043bf49 100644
> > --- a/arch/powerpc/kernel/time.c
> > +++ b/arch/powerpc/kernel/time.c
> > @@ -55,8 +55,9 @@
> >   #include <linux/sched/cputime.h>
> >   #include <linux/sched/clock.h>
> >   #include <linux/processor.h>
> > -#include <asm/trace.h>
> > +#include <linux/mc146818rtc.h>
>
> I'm fine with that but I really think my suggestion to make the rtc_lock
> local to the platforms was better because it is only used to synchronize
> between concurrent invocations of chrp_set_rtc_time or
> maple_set_rtc_time. The rtc core will never do that and the only case
> would be concurrent calls to rtc_ops.set_time and
> update_persistent_clock64 (which should also be removed at some point).

I agree but I think it must be done carefully. If the lock is local to the driver really and without 
a link with the RTC core, then the lock var should probably be static. But then we'll have name 
conflict with the global rtc_lock which is declared in <linux/mc146818rtc.h>

All this is not easy, and I like your idea in the other mail to really clean up the rtc core and 
remove this global rtc_lock completely.

For the time being I guess the fix provided by this patch is just semantic and is just fine as is, 
as there is no real bug behind the messages from sparse.

Christophe