linux-kernel - Re: [PATCH v7 09/11] entry: Add has_syscall

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Message-ID: <e37844e3-8810-42c1-bae1-30b2e7868b80@arm.com>
Date: Tue, 18 Nov 2025 18:13:49 +0100
From: Kevin Brodsky <kevin.brodsky@....com>
To: Jinjie Ruan <ruanjinjie@...wei.com>, catalin.marinas@....com,
 will@...nel.org, oleg@...hat.com, tglx@...utronix.de, peterz@...radead.org,
 luto@...nel.org, shuah@...nel.org, kees@...nel.org, wad@...omium.org,
 akpm@...ux-foundation.org, ldv@...ace.io, macro@...am.me.uk, deller@....de,
 mark.rutland@....com, song@...nel.org, mbenes@...e.cz, ryan.roberts@....com,
 ada.coupriediaz@....com, anshuman.khandual@....com, broonie@...nel.org,
 pengcan@...inos.cn, dvyukov@...gle.com, kmal@...k.li, lihongbo22@...wei.com,
 linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
 linux-kselftest@...r.kernel.org
Subject: Re: [PATCH v7 09/11] entry: Add has_syscall_work() helper

On 17/11/2025 14:30, Jinjie Ruan wrote:
> Add has_syscall_work() helper to facilitate reuse of this
> function in other places.
>
> No functional changes.
>
> Signed-off-by: Jinjie Ruan <ruanjinjie@...wei.com>
> ---
>  include/linux/entry-common.h | 7 ++++++-
>  1 file changed, 6 insertions(+), 1 deletion(-)
>
> diff --git a/include/linux/entry-common.h b/include/linux/entry-common.h
> index cd6dacb2d8bf..e0f94e937e84 100644
> --- a/include/linux/entry-common.h
> +++ b/include/linux/entry-common.h
> @@ -44,6 +44,11 @@
>  				 SYSCALL_WORK_SYSCALL_EXIT_TRAP	|	\
>  				 ARCH_SYSCALL_WORK_EXIT)
>  
> +static inline bool has_syscall_work(unsigned long work)
> +{
> +	return unlikely(work & SYSCALL_WORK_ENTER);

I'm not sure this is a good idea, since the generic syscall machinery
has two separate sets of flags (SYSCALL_WORK_ENTER and
SYSCALL_WORK_EXIT). Of course we could reflect that in the helper's
name, but since it's only used twice after patch 10, maybe we don't need
a helper at all.

- Kevin

> +}
> +
>  /**
>   * syscall_enter_from_user_mode_prepare - Establish state and enable interrupts
>   * @regs:	Pointer to currents pt_regs
> @@ -91,7 +96,7 @@ static __always_inline long syscall_enter_from_user_mode_work(struct pt_regs *re
>  {
>  	unsigned long work = READ_ONCE(current_thread_info()->syscall_work);
>  
> -	if (work & SYSCALL_WORK_ENTER)
> +	if (has_syscall_work(work))
>  		syscall = syscall_trace_enter(regs, syscall, work);
>  
>  	return syscall;