Re: [PATCH 09/10] sched/preempt: fix duplicate extern declarations

Re: [PATCH 09/10] sched/preempt: fix duplicate extern declarations

[Safocl]

but it contains `asmlinkage`, which includes `extern "C"` when
`__cplusplus` is defined...

Re: [PATCH 09/10] sched/preempt: fix duplicate extern declarations

[Arnd Bergmann]

On Fri, Nov 13, 2026, at 13:02, Safocl wrote:
> but it contains `asmlinkage`, which includes `extern "C"` when
> `__cplusplus` is defined...

That dates back to the (failed) 1993 experiment with having C++ in
the kernel, and before the split of the uapi headers.

     Arnd

Re: [PATCH 09/10] sched/preempt: fix duplicate extern declarations

[Safocl]

Perhaps it’s worth making a change now to ensure some consistency? At
your discretion, you could remove such `extern` specifiers for
functions entirely (along with `asmlinkage`), as they are redundant —
or, alternatively, remove just one of them.

[PATCH 00/10] Remove duplicate extern declarations

[Safocl Stollmannovic]

Compiling a kernel module with a C++ compiler results in a duplicate
echo ‘extern’ specifier error.
This occurs because the code contains , and
expands to  when processed by a C++ compiler.
The  specifier must be removed.
https://bugzilla.kernel.org/show_bug.cgi?id=222257

Safocl Stollmannovic (10):
  ARM: fix duplicate extern declarations
  loongarch: fix duplicate extern declarations
  microblaze: fix duplicate extern declarations
  MIPS: fix duplicate extern declarations
  openrisc: fix duplicate extern declarations
  riscv: fix duplicate extern declarations
  x86: fix duplicate extern declarations
  drivers: fix duplicate extern declarations
  sched/preempt: fix duplicate extern declarations
  kernel: fix duplicate extern declarations

 arch/arm/include/asm/bug.h                |  2 +-
 arch/arm/include/asm/opcodes.h            |  2 +-
 arch/loongarch/include/asm/idle.h         |  2 +-
 arch/loongarch/include/asm/smp.h          |  4 +-
 arch/loongarch/include/asm/switch_to.h    |  2 +-
 arch/microblaze/include/asm/entry.h       |  2 +-
 arch/microblaze/kernel/microblaze_ksyms.c |  2 +-
 arch/mips/cavium-octeon/setup.c           |  2 +-
 arch/mips/include/asm/bmips.h             |  2 +-
 arch/mips/include/asm/idle.h              |  2 +-
 arch/mips/include/asm/paccess.h           |  4 +-
 arch/mips/include/asm/ptrace.h            |  4 +-
 arch/mips/include/asm/smp.h               |  2 +-
 arch/mips/include/asm/switch_to.h         |  2 +-
 arch/mips/kernel/r4k-bugs64.c             |  2 +-
 arch/mips/kernel/signal-common.h          |  8 ++--
 arch/mips/kernel/traps.c                  | 50 +++++++++++------------
 arch/openrisc/kernel/process.c            |  2 +-
 arch/riscv/include/asm/string.h           | 24 +++++------
 arch/riscv/kernel/process.c               |  4 +-
 arch/riscv/kernel/stacktrace.c            |  2 +-
 arch/x86/include/asm/efi.h                |  2 +-
 arch/x86/include/asm/gsseg.h              |  2 +-
 arch/x86/include/asm/preempt.h            |  8 ++--
 arch/x86/include/asm/processor.h          |  2 +-
 arch/x86/include/asm/suspend.h            |  2 +-
 arch/x86/um/sys_call_table_32.c           |  4 +-
 arch/x86/um/sys_call_table_64.c           |  4 +-
 drivers/soc/bcm/brcmstb/pm/pm.h           |  6 +--
 include/asm-generic/preempt.h             |  4 +-
 include/linux/lockdep.h                   |  2 +-
 include/linux/printk.h                    |  6 +--
 include/linux/sched/task.h                |  2 +-
 include/linux/start_kernel.h              |  2 +-
 include/linux/suspend.h                   |  4 +-
 35 files changed, 88 insertions(+), 88 deletions(-)

-- 
2.56.1

[PATCH 09/10] sched/preempt: fix duplicate extern declarations

[Safocl Stollmannovic]

Compiling a kernel module with a C++ compiler results in a duplicate
echo ‘extern’ specifier error.
This occurs because the code contains , and
expands to  when processed by a C++ compiler.
The  specifier must be removed.
https://bugzilla.kernel.org/show_bug.cgi?id=222257

Signed-off-by: Safocl Stollmannovic <safocl88@gmail.com>
---
 include/asm-generic/preempt.h | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/include/asm-generic/preempt.h b/include/asm-generic/preempt.h
index 1adddeab8..fc0da591d 100644
--- a/include/asm-generic/preempt.h
+++ b/include/asm-generic/preempt.h
@@ -93,8 +93,8 @@ static __always_inline bool should_resched(int preempt_offset)
 }
 
 #ifdef CONFIG_PREEMPTION
-extern asmlinkage void preempt_schedule(void);
-extern asmlinkage void preempt_schedule_notrace(void);
+asmlinkage void preempt_schedule(void);
+asmlinkage void preempt_schedule_notrace(void);
 
 #define __preempt_schedule() preempt_schedule()
 #define __preempt_schedule_notrace() preempt_schedule_notrace()
-- 
2.56.1

Re: [PATCH 09/10] sched/preempt: fix duplicate extern declarations

[Arnd Bergmann]

On Fri, Nov 13, 2026, at 01:14, Safocl Stollmannovic wrote:
> Compiling a kernel module with a C++ compiler results in a duplicate
> echo ‘extern’ specifier error.
> This occurs because the code contains , and
> expands to  when processed by a C++ compiler.
> The  specifier must be removed.
> https://bugzilla.kernel.org/show_bug.cgi?id=222257

The changelog text makes no sense. We don't support building the
kernel with C++ and this is not a user-visible header.

Leaving out the 'extern' in declarations is just a preference
in coding style, no need to send patches for that.

     Arnd