[PATCH -next] arm64: add missing header dependencies

[PATCH -next] arm64: add missing header dependencies

[Gaosheng Cui]

We get one error when building module with processor.h:

./arch/arm64/include/asm/processor.h:263:36: error: implicit declaration of function ‘task_stack_page’;
  ((struct pt_regs *)(THREAD_SIZE + task_stack_page(p)) - 1)
./arch/arm64/include/asm/processor.h:266:42: note: in expansion of macro ‘task_pt_regs’
 #define KSTK_ESP(tsk) user_stack_pointer(task_pt_regs(tsk))

task_stack_page is declared in linux/sched/task_stack.h, so this patch
add the missing header dependencies.

Signed-off-by: Gaosheng Cui <cuigaosheng1@huawei.com>
---
 arch/arm64/include/asm/processor.h | 1 +
 1 file changed, 1 insertion(+)

diff --git a/arch/arm64/include/asm/processor.h b/arch/arm64/include/asm/processor.h
index 73e38d9a540c..1c239841c4d6 100644
--- a/arch/arm64/include/asm/processor.h
+++ b/arch/arm64/include/asm/processor.h
@@ -28,6 +28,7 @@
 #include <linux/build_bug.h>
 #include <linux/cache.h>
 #include <linux/init.h>
+#include <linux/sched/task_stack.h>
 #include <linux/stddef.h>
 #include <linux/string.h>
 #include <linux/thread_info.h>
-- 
2.25.1

Re: [PATCH -next] arm64: add missing header dependencies

[Will Deacon]

On Mon, May 09, 2022 at 02:17:51PM +0800, Gaosheng Cui wrote:
> We get one error when building module with processor.h:
> 
> ./arch/arm64/include/asm/processor.h:263:36: error: implicit declaration of function ‘task_stack_page’;
>   ((struct pt_regs *)(THREAD_SIZE + task_stack_page(p)) - 1)
> ./arch/arm64/include/asm/processor.h:266:42: note: in expansion of macro ‘task_pt_regs’
>  #define KSTK_ESP(tsk) user_stack_pointer(task_pt_regs(tsk))
> 
> task_stack_page is declared in linux/sched/task_stack.h, so this patch
> add the missing header dependencies.
> 
> Signed-off-by: Gaosheng Cui <cuigaosheng1@huawei.com>
> ---
>  arch/arm64/include/asm/processor.h | 1 +
>  1 file changed, 1 insertion(+)

Do you know which commit is causing this error? I haven't seen any other
reports, but it's hard to know which tree should take your patch as it
stands.

Thanks,

Will

> diff --git a/arch/arm64/include/asm/processor.h b/arch/arm64/include/asm/processor.h
> index 73e38d9a540c..1c239841c4d6 100644
> --- a/arch/arm64/include/asm/processor.h
> +++ b/arch/arm64/include/asm/processor.h
> @@ -28,6 +28,7 @@
>  #include <linux/build_bug.h>
>  #include <linux/cache.h>
>  #include <linux/init.h>
> +#include <linux/sched/task_stack.h>
>  #include <linux/stddef.h>
>  #include <linux/string.h>
>  #include <linux/thread_info.h>
> -- 
> 2.25.1
> 

Re: [PATCH -next] arm64: add missing header dependencies

[Mark Rutland]

On Wed, May 11, 2022 at 09:39:55AM +0800, cuigaosheng wrote:
>     Do you know which commit is causing this error?
> 
> 9cce7a435f89 arm64: CPU support I got the error when building a module with
> processor.h on arm64 and the module calls the KSTK_ESP macro,

I assume that's an out-of-tree module?

Looking at v5.18-rc5, the only users of KSTK_ESP() on arm64 are built in:

| [mark@lakrids:~/src/linux]% git grep KSTK_ESP
| arch/alpha/include/asm/processor.h:#define KSTK_ESP(tsk) \
| arch/arc/include/asm/processor.h:#define KSTK_ESP(tsk)   (task_pt_regs(tsk)->sp)
| arch/arm/include/asm/processor.h:#define KSTK_ESP(tsk)  task_pt_regs(tsk)->ARM_sp
| arch/arm64/include/asm/processor.h:#define KSTK_ESP(tsk)        user_stack_pointer(task_pt_regs(tsk))
| arch/csky/include/asm/processor.h:#define KSTK_ESP(tsk)         (task_pt_regs(tsk)->usp)
| arch/h8300/include/asm/processor.h:#define      KSTK_ESP(tsk)   ((tsk) == current ? rdusp() : (tsk)->thread.usp)
| arch/hexagon/include/asm/processor.h:#define KSTK_ESP(tsk) (pt_psp(task_pt_regs(tsk)))
| arch/ia64/include/asm/processor.h:#define KSTK_ESP(tsk)  ((tsk)->thread.ksp)
| arch/m68k/include/asm/processor.h:#define       KSTK_ESP(tsk)   ((tsk) == current ? rdusp() : (tsk)->thread.usp)
| arch/microblaze/include/asm/processor.h:#  define KSTK_ESP(task)        (task_sp(task))
| arch/mips/include/asm/processor.h:#define KSTK_ESP(tsk) (task_pt_regs(tsk)->regs[29])
| arch/nios2/include/asm/processor.h:#define KSTK_ESP(tsk)        ((tsk)->thread.kregs->sp)
| arch/openrisc/include/asm/processor.h:#define KSTK_ESP(tsk)   (task_pt_regs(tsk)->sp)
| arch/parisc/include/asm/processor.h:#define KSTK_ESP(tsk)       ((tsk)->thread.regs.gr[30])
| arch/powerpc/include/asm/processor.h:#define KSTK_ESP(tsk)  ((tsk)->thread.regs? (tsk)->thread.regs->gpr[1]: 0)
| arch/riscv/include/asm/processor.h:#define KSTK_ESP(tsk)                (task_pt_regs(tsk)->sp)
| arch/s390/include/asm/processor.h:#define KSTK_ESP(tsk) (task_pt_regs(tsk)->gprs[15])
| arch/sh/include/asm/processor_32.h:#define KSTK_ESP(tsk)  (task_pt_regs(tsk)->regs[15])
| arch/sparc/include/asm/processor_32.h:#define KSTK_ESP(tsk)  ((tsk)->thread.kregs->u_regs[UREG_FP])
| arch/sparc/include/asm/processor_64.h:#define KSTK_ESP(tsk)  (task_pt_regs(tsk)->u_regs[UREG_FP])
| arch/um/include/asm/stacktrace.h:       return (unsigned long *)KSTK_ESP(task);
| arch/x86/include/asm/processor.h:#define KSTK_ESP(task)         (task_pt_regs(task)->sp)
| arch/x86/include/asm/processor.h:extern unsigned long KSTK_ESP(struct task_struct *task);
| arch/x86/kernel/process_64.c:unsigned long KSTK_ESP(struct task_struct *task)
| arch/x86/um/asm/processor.h:#define KSTK_ESP(tsk) KSTK_REG(tsk, HOST_SP)
| arch/xtensa/include/asm/processor.h:#define KSTK_ESP(tsk)               (task_pt_regs(tsk)->areg[1])
| fs/proc/array.c:                                esp = KSTK_ESP(task);
| mm/util.c:      return (vma->vm_start <= KSTK_ESP(t) && vma->vm_end >= KSTK_ESP(t));

... or is that module being added in another tree at the moment?

Thanks,
Mark.

> we can also add
> additional header file dependencies(linux/sched/task_stack.h) in the module to
> avoid this error. Maybe perfecting header file dependencies of processor.h is a
> better option? Thanks,
> 
> 在 2022/5/10 18:40, Will Deacon 写道:
> 
>     On Mon, May 09, 2022 at 02:17:51PM +0800, Gaosheng Cui wrote:
> 
>         We get one error when building module with processor.h:
> 
>         ./arch/arm64/include/asm/processor.h:263:36: error: implicit declaration of function ‘task_stack_page’;
>           ((struct pt_regs *)(THREAD_SIZE + task_stack_page(p)) - 1)
>         ./arch/arm64/include/asm/processor.h:266:42: note: in expansion of macro ‘task_pt_regs’
>          #define KSTK_ESP(tsk) user_stack_pointer(task_pt_regs(tsk))
> 
>         task_stack_page is declared in linux/sched/task_stack.h, so this patch
>         add the missing header dependencies.
> 
>         Signed-off-by: Gaosheng Cui <cuigaosheng1@huawei.com>
>         ---
>          arch/arm64/include/asm/processor.h | 1 +
>          1 file changed, 1 insertion(+)
> 
>     Do you know which commit is causing this error? I haven't seen any other
>     reports, but it's hard to know which tree should take your patch as it
>     stands.
> 
>     Thanks,
> 
>     Will
> 
> 
>         diff --git a/arch/arm64/include/asm/processor.h b/arch/arm64/include/asm/processor.h
>         index 73e38d9a540c..1c239841c4d6 100644
>         --- a/arch/arm64/include/asm/processor.h
>         +++ b/arch/arm64/include/asm/processor.h
>         @@ -28,6 +28,7 @@
>          #include <linux/build_bug.h>
>          #include <linux/cache.h>
>          #include <linux/init.h>
>         +#include <linux/sched/task_stack.h>
>          #include <linux/stddef.h>
>          #include <linux/string.h>
>          #include <linux/thread_info.h>
>         --
>         2.25.1
> 
> 
>     .
> 

Re: [PATCH -next] arm64: add missing header dependencies

[kernel test robot]

Hi Gaosheng,

Thank you for the patch! Yet something to improve:

[auto build test ERROR on next-20220506]

url:    https://github.com/intel-lab-lkp/linux/commits/Gaosheng-Cui/arm64-add-missing-header-dependencies/20220509-142946
base:    38a288f5941ef03752887ad86f2d85442358c99a
config: arm64-allyesconfig (https://download.01.org/0day-ci/archive/20220513/202205131035.qIYEFTpo-lkp@intel.com/config)
compiler: aarch64-linux-gcc (GCC) 11.3.0
reproduce (this is a W=1 build):
        wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross
        chmod +x ~/bin/make.cross
        # https://github.com/intel-lab-lkp/linux/commit/05d29bfe89ad4e7205d77fcdd8199dd6544ff784
        git remote add linux-review https://github.com/intel-lab-lkp/linux
        git fetch --no-tags linux-review Gaosheng-Cui/arm64-add-missing-header-dependencies/20220509-142946
        git checkout 05d29bfe89ad4e7205d77fcdd8199dd6544ff784
        # save the config file
        mkdir build_dir && cp config build_dir/.config
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=gcc-11.3.0 make.cross W=1 O=build_dir ARCH=arm64 prepare

If you fix the issue, kindly add following tag as appropriate
Reported-by: kernel test robot <lkp@intel.com>

All error/warnings (new ones prefixed by >>):

   scripts/genksyms/parse.y: warning: 9 shift/reduce conflicts [-Wconflicts-sr]
   scripts/genksyms/parse.y: warning: 5 reduce/reduce conflicts [-Wconflicts-rr]
   scripts/genksyms/parse.y: note: rerun with option '-Wcounterexamples' to generate conflict counterexamples
   In file included from include/linux/ipc.h:7,
                    from include/uapi/linux/sem.h:5,
                    from include/linux/sem.h:5,
                    from include/linux/sched.h:15,
                    from include/linux/sched/task_stack.h:9,
                    from arch/arm64/include/asm/processor.h:31,
                    from include/linux/mutex.h:19,
                    from include/linux/kernfs.h:11,
                    from include/linux/sysfs.h:16,
                    from include/linux/kobject.h:20,
                    from include/linux/of.h:17,
                    from include/linux/irqdomain.h:35,
                    from include/linux/acpi.h:13,
                    from include/acpi/apei.h:9,
                    from include/acpi/ghes.h:5,
                    from include/linux/arm_sdei.h:8,
                    from arch/arm64/kernel/asm-offsets.c:10:
>> include/linux/rhashtable-types.h:88:41: error: field 'mutex' has incomplete type
      88 |         struct mutex                    mutex;
         |                                         ^~~~~
   In file included from include/linux/hrtimer.h:20,
                    from include/linux/sched.h:19,
                    from include/linux/sched/task_stack.h:9,
                    from arch/arm64/include/asm/processor.h:31,
                    from include/linux/mutex.h:19,
                    from include/linux/kernfs.h:11,
                    from include/linux/sysfs.h:16,
                    from include/linux/kobject.h:20,
                    from include/linux/of.h:17,
                    from include/linux/irqdomain.h:35,
                    from include/linux/acpi.h:13,
                    from include/acpi/apei.h:9,
                    from include/acpi/ghes.h:5,
                    from include/linux/arm_sdei.h:8,
                    from arch/arm64/kernel/asm-offsets.c:10:
   include/linux/seqlock.h: In function '__seqprop_mutex_sequence':
>> include/linux/seqlock.h:277:86: error: implicit declaration of function 'mutex_lock' [-Werror=implicit-function-declaration]
     277 | SEQCOUNT_LOCKNAME(mutex,        struct mutex,    true,     s->lock,        mutex,    mutex_lock(s->lock))
         |                                                                                      ^~~~~~~~~~
   include/linux/seqlock.h:151:33: note: in definition of macro '__SEQ_LOCK'
     151 | #define __SEQ_LOCK(expr)        expr
         |                                 ^~~~
   include/linux/seqlock.h:277:1: note: in expansion of macro 'SEQCOUNT_LOCKNAME'
     277 | SEQCOUNT_LOCKNAME(mutex,        struct mutex,    true,     s->lock,        mutex,    mutex_lock(s->lock))
         | ^~~~~~~~~~~~~~~~~
>> include/linux/seqlock.h:277:76: error: implicit declaration of function 'mutex_unlock'; did you mean 'write_unlock'? [-Werror=implicit-function-declaration]
     277 | SEQCOUNT_LOCKNAME(mutex,        struct mutex,    true,     s->lock,        mutex,    mutex_lock(s->lock))
         |                                                                            ^~~~~
   include/linux/seqlock.h:151:33: note: in definition of macro '__SEQ_LOCK'
     151 | #define __SEQ_LOCK(expr)        expr
         |                                 ^~~~
   include/linux/seqlock.h:277:1: note: in expansion of macro 'SEQCOUNT_LOCKNAME'
     277 | SEQCOUNT_LOCKNAME(mutex,        struct mutex,    true,     s->lock,        mutex,    mutex_lock(s->lock))
         | ^~~~~~~~~~~~~~~~~
   include/linux/seqlock.h: In function '__seqprop_mutex_assert':
>> include/linux/lockdep.h:282:61: error: invalid use of undefined type 'struct mutex'
     282 | #define lockdep_is_held(lock)           lock_is_held(&(lock)->dep_map)
         |                                                             ^~
   include/linux/seqlock.h:151:33: note: in definition of macro '__SEQ_LOCK'
     151 | #define __SEQ_LOCK(expr)        expr
         |                                 ^~~~
   include/linux/lockdep.h:306:14: note: in expansion of macro 'WARN_ON'
     306 |         do { WARN_ON(debug_locks && !(cond)); } while (0)
         |              ^~~~~~~
   include/linux/lockdep.h:312:9: note: in expansion of macro 'lockdep_assert'
     312 |         lockdep_assert(lockdep_is_held(l) != LOCK_STATE_NOT_HELD)
         |         ^~~~~~~~~~~~~~
   include/linux/lockdep.h:312:24: note: in expansion of macro 'lockdep_is_held'
     312 |         lockdep_assert(lockdep_is_held(l) != LOCK_STATE_NOT_HELD)
         |                        ^~~~~~~~~~~~~~~
   include/linux/seqlock.h:245:20: note: in expansion of macro 'lockdep_assert_held'
     245 |         __SEQ_LOCK(lockdep_assert_held(lockmember));                    \
         |                    ^~~~~~~~~~~~~~~~~~~
   include/linux/seqlock.h:277:1: note: in expansion of macro 'SEQCOUNT_LOCKNAME'
     277 | SEQCOUNT_LOCKNAME(mutex,        struct mutex,    true,     s->lock,        mutex,    mutex_lock(s->lock))
         | ^~~~~~~~~~~~~~~~~
   include/linux/seqlock.h: In function 'read_seqbegin':
>> include/linux/seqlock.h:330:17: error: implicit declaration of function 'cpu_relax' [-Werror=implicit-function-declaration]
     330 |                 cpu_relax();                                            \
         |                 ^~~~~~~~~
   include/linux/seqlock.h:344:25: note: in expansion of macro '__read_seqcount_begin'
     344 |         unsigned _seq = __read_seqcount_begin(s);                       \
         |                         ^~~~~~~~~~~~~~~~~~~~~
   include/linux/seqlock.h:359:9: note: in expansion of macro 'raw_read_seqcount_begin'
     359 |         raw_read_seqcount_begin(s);                                     \
         |         ^~~~~~~~~~~~~~~~~~~~~~~
   include/linux/seqlock.h:836:24: note: in expansion of macro 'read_seqcount_begin'
     836 |         unsigned ret = read_seqcount_begin(&sl->seqcount);
         |                        ^~~~~~~~~~~~~~~~~~~
   In file included from include/linux/sched/task_stack.h:9,
                    from arch/arm64/include/asm/processor.h:31,
                    from include/linux/mutex.h:19,
                    from include/linux/kernfs.h:11,
                    from include/linux/sysfs.h:16,
                    from include/linux/kobject.h:20,
                    from include/linux/of.h:17,
                    from include/linux/irqdomain.h:35,
                    from include/linux/acpi.h:13,
                    from include/acpi/apei.h:9,
                    from include/acpi/ghes.h:5,
                    from include/linux/arm_sdei.h:8,
                    from arch/arm64/kernel/asm-offsets.c:10:
   include/linux/sched.h: At top level:
>> include/linux/sched.h:1227:41: error: field 'futex_exit_mutex' has incomplete type
    1227 |         struct mutex                    futex_exit_mutex;
         |                                         ^~~~~~~~~~~~~~~~
>> include/linux/sched.h:1232:41: error: field 'perf_event_mutex' has incomplete type
    1232 |         struct mutex                    perf_event_mutex;
         |                                         ^~~~~~~~~~~~~~~~
>> include/linux/sched.h:1512:41: error: field 'thread' has incomplete type
    1512 |         struct thread_struct            thread;
         |                                         ^~~~~~
   In file included from include/vdso/processor.h:10,
                    from arch/arm64/include/asm/processor.h:36,
                    from include/linux/mutex.h:19,
                    from include/linux/kernfs.h:11,
                    from include/linux/sysfs.h:16,
                    from include/linux/kobject.h:20,
                    from include/linux/of.h:17,
                    from include/linux/irqdomain.h:35,
                    from include/linux/acpi.h:13,
                    from include/acpi/apei.h:9,
                    from include/acpi/ghes.h:5,
                    from include/linux/arm_sdei.h:8,
                    from arch/arm64/kernel/asm-offsets.c:10:
>> arch/arm64/include/asm/vdso/processor.h:10:20: warning: conflicting types for 'cpu_relax'; have 'void(void)'
      10 | static inline void cpu_relax(void)
         |                    ^~~~~~~~~
>> arch/arm64/include/asm/vdso/processor.h:10:20: error: static declaration of 'cpu_relax' follows non-static declaration
   In file included from include/linux/hrtimer.h:20,
                    from include/linux/sched.h:19,
                    from include/linux/sched/task_stack.h:9,
                    from arch/arm64/include/asm/processor.h:31,
                    from include/linux/mutex.h:19,
                    from include/linux/kernfs.h:11,
                    from include/linux/sysfs.h:16,
                    from include/linux/kobject.h:20,
                    from include/linux/of.h:17,
                    from include/linux/irqdomain.h:35,
                    from include/linux/acpi.h:13,
                    from include/acpi/apei.h:9,
                    from include/acpi/ghes.h:5,
                    from include/linux/arm_sdei.h:8,
                    from arch/arm64/kernel/asm-offsets.c:10:
   include/linux/seqlock.h:330:17: note: previous implicit declaration of 'cpu_relax' with type 'void(void)'
     330 |                 cpu_relax();                                            \
         |                 ^~~~~~~~~
   include/linux/seqlock.h:344:25: note: in expansion of macro '__read_seqcount_begin'
     344 |         unsigned _seq = __read_seqcount_begin(s);                       \
         |                         ^~~~~~~~~~~~~~~~~~~~~
   include/linux/seqlock.h:359:9: note: in expansion of macro 'raw_read_seqcount_begin'
     359 |         raw_read_seqcount_begin(s);                                     \
         |         ^~~~~~~~~~~~~~~~~~~~~~~
   include/linux/seqlock.h:836:24: note: in expansion of macro 'read_seqcount_begin'
     836 |         unsigned ret = read_seqcount_begin(&sl->seqcount);
         |                        ^~~~~~~~~~~~~~~~~~~
   In file included from include/linux/mutex.h:19,
                    from include/linux/kernfs.h:11,
                    from include/linux/sysfs.h:16,
                    from include/linux/kobject.h:20,
                    from include/linux/of.h:17,
                    from include/linux/irqdomain.h:35,
                    from include/linux/acpi.h:13,
                    from include/acpi/apei.h:9,
                    from include/acpi/ghes.h:5,
                    from include/linux/arm_sdei.h:8,
                    from arch/arm64/kernel/asm-offsets.c:10:
>> arch/arm64/include/asm/processor.h:70: warning: "TASK_SIZE_OF" redefined
      70 | #define TASK_SIZE_OF(tsk)       (test_tsk_thread_flag(tsk, TIF_32BIT) ? \
         | 
   In file included from include/linux/sched/task_stack.h:9,
                    from arch/arm64/include/asm/processor.h:31,
                    from include/linux/mutex.h:19,
                    from include/linux/kernfs.h:11,
                    from include/linux/sysfs.h:16,
                    from include/linux/kobject.h:20,
                    from include/linux/of.h:17,
                    from include/linux/irqdomain.h:35,
                    from include/linux/acpi.h:13,
                    from include/acpi/apei.h:9,
                    from include/acpi/ghes.h:5,
                    from include/linux/arm_sdei.h:8,
                    from arch/arm64/kernel/asm-offsets.c:10:
   include/linux/sched.h:2248: note: this is the location of the previous definition
    2248 | #define TASK_SIZE_OF(tsk)       TASK_SIZE
         | 
   In file included from include/linux/kernfs.h:11,
                    from include/linux/sysfs.h:16,
                    from include/linux/kobject.h:20,
                    from include/linux/of.h:17,
                    from include/linux/irqdomain.h:35,
                    from include/linux/acpi.h:13,
                    from include/acpi/apei.h:9,
                    from include/acpi/ghes.h:5,
                    from include/linux/arm_sdei.h:8,
                    from arch/arm64/kernel/asm-offsets.c:10:
>> include/linux/mutex.h:218:13: warning: conflicting types for 'mutex_unlock'; have 'void(struct mutex *)'
     218 | extern void mutex_unlock(struct mutex *lock);
         |             ^~~~~~~~~~~~
   In file included from include/linux/hrtimer.h:20,
                    from include/linux/sched.h:19,
                    from include/linux/sched/task_stack.h:9,
                    from arch/arm64/include/asm/processor.h:31,
                    from include/linux/mutex.h:19,
                    from include/linux/kernfs.h:11,
                    from include/linux/sysfs.h:16,
                    from include/linux/kobject.h:20,
                    from include/linux/of.h:17,
                    from include/linux/irqdomain.h:35,
                    from include/linux/acpi.h:13,
                    from include/acpi/apei.h:9,
                    from include/acpi/ghes.h:5,
                    from include/linux/arm_sdei.h:8,
                    from arch/arm64/kernel/asm-offsets.c:10:
   include/linux/seqlock.h:277:76: note: previous implicit declaration of 'mutex_unlock' with type 'void(struct mutex *)'
     277 | SEQCOUNT_LOCKNAME(mutex,        struct mutex,    true,     s->lock,        mutex,    mutex_lock(s->lock))
         |                                                                            ^~~~~
   include/linux/seqlock.h:151:33: note: in definition of macro '__SEQ_LOCK'
     151 | #define __SEQ_LOCK(expr)        expr
         |                                 ^~~~
   include/linux/seqlock.h:277:1: note: in expansion of macro 'SEQCOUNT_LOCKNAME'
     277 | SEQCOUNT_LOCKNAME(mutex,        struct mutex,    true,     s->lock,        mutex,    mutex_lock(s->lock))
         | ^~~~~~~~~~~~~~~~~
   cc1: some warnings being treated as errors
   make[2]: *** [scripts/Makefile.build:122: arch/arm64/kernel/asm-offsets.s] Error 1
   make[2]: Target '__build' not remade because of errors.
   make[1]: *** [Makefile:1284: prepare0] Error 2
   make[1]: Target 'prepare' not remade because of errors.
   make: *** [Makefile:226: __sub-make] Error 2
   make: Target 'prepare' not remade because of errors.


vim +/cpu_relax +10 arch/arm64/include/asm/vdso/processor.h

f511e079177a9b Vincenzo Frascino 2020-03-20   9  
f511e079177a9b Vincenzo Frascino 2020-03-20 @10  static inline void cpu_relax(void)
f511e079177a9b Vincenzo Frascino 2020-03-20  11  {
f511e079177a9b Vincenzo Frascino 2020-03-20  12  	asm volatile("yield" ::: "memory");
f511e079177a9b Vincenzo Frascino 2020-03-20  13  }
f511e079177a9b Vincenzo Frascino 2020-03-20  14  

-- 
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