[PATCH v2 10/10] kernel: fix duplicate extern declarations

[Safocl Stollmannovic]

Compiling a kernel module with a C++ compiler results in a "duplicate
extern specifier" error.
This occurs because the code contains `extern asmlinkage`, and `asmlinkage`
expands to `extern C` when processed by a C++ compiler.
Since the code already contains sections that respond to a C++ compiler,
I believe it is a perfectly valid approach to gradually move toward a state
where kernel modules can be compiled by a C++ compiler without any issues.
The `extern` specifier must be removed.

Link: https://bugzilla.kernel.org/show_bug.cgi?id=222257

Signed-off-by: Safocl Stollmannovic <safocl88@xxxxxxxxx>
---
 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 ++--
 5 files changed, 8 insertions(+), 8 deletions(-)

diff --git a/include/linux/lockdep.h b/include/linux/lockdep.h
index a6451ecbb..f436eab07 100644
--- a/include/linux/lockdep.h
+++ b/include/linux/lockdep.h
@@ -89,7 +89,7 @@ extern void lockdep_init(void);
 extern void lockdep_reset(void);
 extern void lockdep_reset_lock(struct lockdep_map *lock);
 extern void lockdep_free_key_range(void *start, unsigned long size);
-extern asmlinkage void lockdep_sys_exit(void);
+asmlinkage void lockdep_sys_exit(void);
 extern void lockdep_set_selftest_task(struct task_struct *task);
 
 extern void lockdep_init_task(struct task_struct *task);
diff --git a/include/linux/printk.h b/include/linux/printk.h
index f594c1266..09a28181e 100644
--- a/include/linux/printk.h
+++ b/include/linux/printk.h
@@ -136,7 +136,7 @@ struct va_format {
 })
 
 #ifdef CONFIG_EARLY_PRINTK
-extern asmlinkage __printf(1, 2)
+asmlinkage __printf(1, 2)
 void early_printk(const char *fmt, ...);
 #else
 static inline __printf(1, 2) __cold
@@ -200,8 +200,8 @@ void __init setup_log_buf(int early);
 __printf(1, 2) void dump_stack_set_arch_desc(const char *fmt, ...);
 void dump_stack_print_info(const char *log_lvl);
 void show_regs_print_info(const char *log_lvl);
-extern asmlinkage void dump_stack_lvl(const char *log_lvl) __cold;
-extern asmlinkage void dump_stack(void) __cold;
+asmlinkage void dump_stack_lvl(const char *log_lvl) __cold;
+asmlinkage void dump_stack(void) __cold;
 void printk_trigger_flush(void);
 void console_try_replay_all(void);
 void printk_legacy_allow_panic_sync(void);
diff --git a/include/linux/sched/task.h b/include/linux/sched/task.h
index 90ed5bc3c..5cdef6b0f 100644
--- a/include/linux/sched/task.h
+++ b/include/linux/sched/task.h
@@ -61,7 +61,7 @@ extern struct task_struct init_task;
 
 extern int lockdep_tasklist_lock_is_held(void);
 
-extern asmlinkage void schedule_tail(struct task_struct *prev);
+asmlinkage void schedule_tail(struct task_struct *prev);
 extern void init_idle(struct task_struct *idle, int cpu);
 
 extern int sched_fork(u64 clone_flags, struct task_struct *p);
diff --git a/include/linux/start_kernel.h b/include/linux/start_kernel.h
index 09f994ac8..5855467ca 100644
--- a/include/linux/start_kernel.h
+++ b/include/linux/start_kernel.h
@@ -8,6 +8,6 @@
 /* Define the prototype for start_kernel here, rather than cluttering
    up something else. */
 
-extern asmlinkage void __init __noreturn start_kernel(void);
+asmlinkage void __init __noreturn start_kernel(void);
 
 #endif /* _LINUX_START_KERNEL_H */
diff --git a/include/linux/suspend.h b/include/linux/suspend.h
index a38150277..b97af3420 100644
--- a/include/linux/suspend.h
+++ b/include/linux/suspend.h
@@ -385,8 +385,8 @@ extern int swsusp_page_is_forbidden(struct page *);
 extern void swsusp_set_page_free(struct page *);
 extern void swsusp_unset_page_free(struct page *);
 extern unsigned long get_safe_page(gfp_t gfp_mask);
-extern asmlinkage int swsusp_arch_suspend(void);
-extern asmlinkage int swsusp_arch_resume(void);
+asmlinkage int swsusp_arch_suspend(void);
+asmlinkage int swsusp_arch_resume(void);
 
 extern u32 swsusp_hardware_signature;
 extern void hibernation_set_ops(const struct platform_hibernation_ops *ops);
-- 
2.56.1