On Tue, Sep 25, 2018 at 07:34:15AM +0200, Christophe LEROY wrote:
>
>
> Le 24/09/2018 à 17:52, Christophe Leroy a écrit :
> > When switching powerpc to CONFIG_THREAD_INFO_IN_TASK, include/sched.h
> > has to be included in asm/smp.h for the following change, in order
> > to avoid uncomplete definition of task_struct:
> >
> > -#define raw_smp_processor_id() (current_thread_info()->cpu)
> > +#define raw_smp_processor_id() (current->cpu)
> >
> > But this generates the following compilation error, due to circular
> > header dependency.
> >
> > CC kernel/time/alarmtimer.o
> > In file included from ./arch/powerpc/include/asm/smp.h:31,
> > from ./include/linux/smp.h:64,
> > from ./include/linux/percpu.h:7,
> > from ./include/linux/hrtimer.h:22,
> > from kernel/time/alarmtimer.c:19:
> > ./include/linux/sched.h:558:19: error: field 'dl_timer' has incomplete type
> > struct hrtimer dl_timer;
> > ^~~~~~~~
> > ./include/linux/sched.h:567:17: error: field 'inactive_timer' has incomplete type
> > struct hrtimer inactive_timer;
> > ^~~~~~~~~~~~~~
> > make[1]: *** [kernel/time/alarmtimer.o] Error 1
> > make: *** [kernel/time/alarmtimer.o] Error 2
> >
> > CC fs/timerfd.o
> > In file included from ./arch/powerpc/include/asm/smp.h:31,
> > from ./include/linux/smp.h:64,
> > from ./include/linux/percpu.h:7,
> > from ./include/linux/hrtimer.h:22,
> > from ./include/linux/alarmtimer.h:6,
> > from fs/timerfd.c:12:
> > ./include/linux/sched.h:558:19: error: field 'dl_timer' has incomplete type
> > struct hrtimer dl_timer;
> > ^~~~~~~~
> > ./include/linux/sched.h:567:17: error: field 'inactive_timer' has incomplete type
> > struct hrtimer inactive_timer;
> > ^~~~~~~~~~~~~~
> > make[1]: *** [fs/timerfd.o] Error 1
> > make: *** [fs/timerfd.o] Error 2
> >
> > This patch fixes it by including linux/hrtimer.h after linux/sched.h
> >
> > Signed-off-by: Christophe Leroy <christophe.leroy@xxxxxx>
> > ---
> > Should it be fixed in powerpc instead ? In that case, how ? Any idea ?
>
>
> Looks like there are several other places where the problem occurs, so it
> has to be fixed in the powerpc headers instead.
>
> Seems like RISC arch faced the same issue, and fixed it the following way:
>
> /*
> * This is particularly ugly: it appears we can't actually get the
> definition
> * of task_struct here, but we need access to the CPU this task is running
> on.
> * Instead of using C we're using asm-offsets.h to get the current processor
> * ID.
> */
> #define raw_smp_processor_id() (*((int*)((char*)get_current() +
> TASK_TI_CPU)))
>
>
> Unless someone has a better idea, I'll fixed it that way.
To solve this on arm64 we made the cpu number a percpu variable; see
commit:
57c82954e77fa12c ("arm64: make cpu number a percpu variable")
IIUC, you could do that by placing it in paca_struct.
Thanks,
Mark.
