linux-kernel - Re: [PATCH] hw_breakpoint: Fix build warnings with clang

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Date:   Tue, 2 Jun 2020 07:10:55 +0200
From:   Christophe Leroy <christophe.leroy@...roup.eu>
To:     Ravi Bangoria <ravi.bangoria@...ux.ibm.com>, mpe@...erman.id.au
Cc:     christophe.leroy@....fr, mikey@...ling.org, apopple@...ux.ibm.com,
        linux-kernel@...r.kernel.org, npiggin@...il.com, paulus@...ba.org,
        naveen.n.rao@...ux.vnet.ibm.com, linuxppc-dev@...ts.ozlabs.org
Subject: Re: [PATCH] hw_breakpoint: Fix build warnings with clang



Le 02/06/2020 à 06:12, Ravi Bangoria a écrit :
> kbuild test robot reported few build warnings with hw_breakpoint code
> when compiled with clang[1]. Fix those.
> 
> [1]: https://lore.kernel.org/linuxppc-dev/202005192233.oi9CjRtA%25lkp@intel.com/
> 
> Reported-by: kbuild test robot <lkp@...el.com>
> Signed-off-by: Ravi Bangoria <ravi.bangoria@...ux.ibm.com>
> ---
> Note: Prepared on top of powerpc/next.
> 
>   arch/powerpc/include/asm/hw_breakpoint.h | 3 ---
>   include/linux/hw_breakpoint.h            | 4 ++++
>   2 files changed, 4 insertions(+), 3 deletions(-)
> 
> diff --git a/arch/powerpc/include/asm/hw_breakpoint.h b/arch/powerpc/include/asm/hw_breakpoint.h
> index f42a55eb77d2..cb424799da0d 100644
> --- a/arch/powerpc/include/asm/hw_breakpoint.h
> +++ b/arch/powerpc/include/asm/hw_breakpoint.h
> @@ -70,9 +70,6 @@ extern int hw_breakpoint_exceptions_notify(struct notifier_block *unused,
>   						unsigned long val, void *data);
>   int arch_install_hw_breakpoint(struct perf_event *bp);
>   void arch_uninstall_hw_breakpoint(struct perf_event *bp);
> -int arch_reserve_bp_slot(struct perf_event *bp);
> -void arch_release_bp_slot(struct perf_event *bp);
> -void arch_unregister_hw_breakpoint(struct perf_event *bp);
>   void hw_breakpoint_pmu_read(struct perf_event *bp);
>   extern void flush_ptrace_hw_breakpoint(struct task_struct *tsk);
>   
> diff --git a/include/linux/hw_breakpoint.h b/include/linux/hw_breakpoint.h
> index 6058c3844a76..521481f0d320 100644
> --- a/include/linux/hw_breakpoint.h
> +++ b/include/linux/hw_breakpoint.h
> @@ -80,6 +80,10 @@ extern int dbg_reserve_bp_slot(struct perf_event *bp);
>   extern int dbg_release_bp_slot(struct perf_event *bp);
>   extern int reserve_bp_slot(struct perf_event *bp);
>   extern void release_bp_slot(struct perf_event *bp);
> +extern int hw_breakpoint_weight(struct perf_event *bp);
> +extern int arch_reserve_bp_slot(struct perf_event *bp);
> +extern void arch_release_bp_slot(struct perf_event *bp);
> +extern void arch_unregister_hw_breakpoint(struct perf_event *bp);

Please no new 'extern'. In the old days 'extern' keyword was used, but 
new code shall not introduce new unnecessary usage of 'extern' keyword. 
See report from Checkpatch below:

WARNING:COMMIT_LOG_LONG_LINE: Possible unwrapped commit description 
(prefer a maximum 75 chars per line)
#9:
[1]: 
https://lore.kernel.org/linuxppc-dev/202005192233.oi9CjRtA%25lkp@intel.com/

CHECK:AVOID_EXTERNS: extern prototypes should be avoided in .h files
#40: FILE: include/linux/hw_breakpoint.h:83:
+extern int hw_breakpoint_weight(struct perf_event *bp);

CHECK:AVOID_EXTERNS: extern prototypes should be avoided in .h files
#41: FILE: include/linux/hw_breakpoint.h:84:
+extern int arch_reserve_bp_slot(struct perf_event *bp);

CHECK:AVOID_EXTERNS: extern prototypes should be avoided in .h files
#42: FILE: include/linux/hw_breakpoint.h:85:
+extern void arch_release_bp_slot(struct perf_event *bp);

CHECK:AVOID_EXTERNS: extern prototypes should be avoided in .h files
#43: FILE: include/linux/hw_breakpoint.h:86:
+extern void arch_unregister_hw_breakpoint(struct perf_event *bp);

total: 0 errors, 1 warnings, 4 checks, 19 lines checked

NOTE: For some of the reported defects, checkpatch may be able to
       mechanically convert to the typical style using --fix or 
--fix-inplace.

the.patch has style problems, please review.

NOTE: Ignored message types: ARCH_INCLUDE_LINUX BIT_MACRO 
COMPARISON_TO_NULL DT_SPLIT_BINDING_PATCH EMAIL_SUBJECT 
FILE_PATH_CHANGES GLOBAL_INITIALISERS LINE_SPACING MULTIPLE_ASSIGNMENTS

NOTE: If any of the errors are false positives, please report
       them to the maintainer, see CHECKPATCH in MAINTAINERS.

Christophe