On 09/25/2018 12:15 PM, Christophe LEROY wrote:

Le 25/09/2018 à 14:11, Mark Rutland a écrit :

quoted

On Tue, Sep 25, 2018 at 07:34:15AM +0200, Christophe LEROY wrote:

quoted

Le 24/09/2018 à 17:52, Christophe Leroy a écrit :

quoted

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 <redacted>
---
   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")

Thanks, I'll have a look

quoted

IIUC, you could do that by placing it in paca_struct.

By the way, it is already in PACA struct for PPC64.
The issue is with PPC32, up to now it was in current_thread_info:

#ifdef CONFIG_PPC64
#define raw_smp_processor_id()    (local_paca->paca_index)
#define hard_smp_processor_id() (get_paca()->hw_cpu_id)
#else
/* 32-bit */
extern int smp_hw_index[];

#define raw_smp_processor_id()    (current_thread_info()->cpu)
#define hard_smp_processor_id()     (smp_hw_index[smp_processor_id()])

[..]

#endif

It seems not that easy. Adding the following leads to the below failure. 
I'm having a hard time identifying and fixing the issue. Looks again 
like a circular thing, because linux/percpu-defs.h is where 
raw_cpu_ptr() is defined.

--- a/arch/powerpc/include/asm/smp.h
+++ b/arch/powerpc/include/asm/smp.h

@@ -83,7 +83,14 @@ int is_cpu_dead(unsigned int cpu);
  /* 32-bit */
  extern int smp_hw_index[];

-#define raw_smp_processor_id() (current_thread_info()->cpu)
+DECLARE_PER_CPU_READ_MOSTLY(unsigned int, cpu_number);
+
+/*
+ * We don't use this_cpu_read(cpu_number) as that has implicit writes to
+ * preempt_count, and associated (compiler) barriers, that we'd like to 

avoid
+ * the expense of. If we're preemptible, the value can be stale at use 
anyway.
+ */
+#define raw_smp_processor_id()         (*this_cpu_ptr(&cpu_number))
  #define hard_smp_processor_id()        (smp_hw_index[smp_processor_id()])

  static inline int get_hard_smp_processor_id(int cpu)


   CC      arch/powerpc/kernel/asm-offsets.s
In file included from ././include/linux/compiler_types.h:64:0,
                  from <command-line>:0:
./include/linux/percpu-rwsem.h: In function 
'percpu_down_read_preempt_disable':
./include/linux/percpu-defs.h:254:27: error: implicit declaration of 
function 'raw_cpu_ptr' [-Werror=implicit-function-declaration]
  #define this_cpu_ptr(ptr) raw_cpu_ptr(ptr)
                            ^
./include/linux/compiler-gcc.h:58:26: note: in definition of macro 
'RELOC_HIDE'
   (typeof(ptr)) (__ptr + (off));     \
                           ^
./include/asm-generic/percpu.h:44:31: note: in expansion of macro 
'SHIFT_PERCPU_PTR'
  #define arch_raw_cpu_ptr(ptr) SHIFT_PERCPU_PTR(ptr, __my_cpu_offset)
                                ^
./include/asm-generic/percpu.h:31:25: note: in expansion of macro 
'per_cpu_offset'
  #define __my_cpu_offset per_cpu_offset(raw_smp_processor_id())
                          ^
./arch/powerpc/include/asm/smp.h:93:35: note: in expansion of macro 
'this_cpu_ptr'
  #define raw_smp_processor_id()  (*this_cpu_ptr(&cpu_number))
                                    ^
./include/asm-generic/percpu.h:31:40: note: in expansion of macro 
'raw_smp_processor_id'
  #define __my_cpu_offset per_cpu_offset(raw_smp_processor_id())
                                         ^
./include/asm-generic/percpu.h:44:53: note: in expansion of macro 
'__my_cpu_offset'
  #define arch_raw_cpu_ptr(ptr) SHIFT_PERCPU_PTR(ptr, __my_cpu_offset)
                                                      ^
./include/linux/percpu-defs.h:244:2: note: in expansion of macro 
'arch_raw_cpu_ptr'
   arch_raw_cpu_ptr(ptr);      \
   ^
./include/asm-generic/percpu.h:76:3: note: in expansion of macro 
'raw_cpu_ptr'
   *raw_cpu_ptr(&(pcp)) op val;     \
    ^
./include/asm-generic/percpu.h:225:34: note: in expansion of macro 
'raw_cpu_generic_to_op'
  #define raw_cpu_add_1(pcp, val)  raw_cpu_generic_to_op(pcp, val, +=)
                                   ^
./include/linux/percpu-defs.h:379:11: note: in expansion of macro 
'raw_cpu_add_1'
    case 1: stem##1(variable, __VA_ARGS__);break;  \
            ^
./include/linux/percpu-defs.h:424:32: note: in expansion of macro 
'__pcpu_size_call'
  #define raw_cpu_add(pcp, val)  __pcpu_size_call(raw_cpu_add_, pcp, val)
                                 ^
./include/linux/percpu-defs.h:460:2: note: in expansion of macro 
'raw_cpu_add'
   raw_cpu_add(pcp, val);      \
   ^
./include/linux/percpu-defs.h:499:30: note: in expansion of macro 
'__this_cpu_add'
  #define __this_cpu_inc(pcp)  __this_cpu_add(pcp, 1)
                               ^
./include/linux/percpu-rwsem.h:47:2: note: in expansion of macro 
'__this_cpu_inc'
   __this_cpu_inc(*sem->read_count);
   ^
./arch/powerpc/include/asm/smp.h:93:34: error: invalid type argument of 
unary '*' (have 'int')
  #define raw_smp_processor_id()  (*this_cpu_ptr(&cpu_number))
                                   ^


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