linux-kernel - Re: [patch 11/12] softirq: Allow inlining do_softirq_own

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Message-ID: <CAJhGHyDF-wuK0Q0RZ9mDTo19rayA-jjJ1SGp2-1TS_d5-eHDzw@mail.gmail.com>
Date:   Fri, 5 Feb 2021 18:14:35 +0800
From:   Lai Jiangshan <jiangshanlai+lkml@...il.com>
To:     Thomas Gleixner <tglx@...utronix.de>
Cc:     LKML <linux-kernel@...r.kernel.org>, X86 ML <x86@...nel.org>,
        Josh Poimboeuf <jpoimboe@...hat.com>,
        Kees Cook <keescook@...omium.org>
Subject: Re: [patch 11/12] softirq: Allow inlining do_softirq_own_stack()

On Fri, Feb 5, 2021 at 10:04 AM Thomas Gleixner <tglx@...utronix.de> wrote:
>
> The function to switch to the irq stack on x86 is now minimal and there is
> only a single caller. Allow the stack switch to be inlined.
>
> Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
> ---
>  include/linux/interrupt.h |    2 ++
>  kernel/softirq.c          |    4 ++++
>  2 files changed, 6 insertions(+)
>
> --- a/include/linux/interrupt.h
> +++ b/include/linux/interrupt.h
> @@ -570,7 +570,9 @@ asmlinkage void do_softirq(void);
>  asmlinkage void __do_softirq(void);
>
>  #ifdef __ARCH_HAS_DO_SOFTIRQ
> +# ifndef __ARCH_HAS_DO_SOFTIRQ_INLINE
>  void do_softirq_own_stack(void);
> +# endif
>  #else
>  static inline void do_softirq_own_stack(void)
>  {

Hello

This patch and the next patch have three "#if[n]def" with
__ARCH_HAS_DO_SOFTIRQ_INLINE and this one is nested in
__ARCH_HAS_DO_SOFTIRQ.

I wonder if we can use __ARCH_HAS_DO_SOFTIRQ only.

For example, we can move "void do_softirq_own_stack(void);" to around
the code where __ARCH_HAS_DO_SOFTIRQ are defined in very ARCHs.
(And for x86, do_softirq_own_stack() is a macro instead of function
declaration as next patch shows)

Thanks
Lai

> --- a/kernel/softirq.c
> +++ b/kernel/softirq.c
> @@ -26,6 +26,10 @@
>  #include <linux/tick.h>
>  #include <linux/irq.h>
>
> +#ifdef __ARCH_HAS_DO_SOFTIRQ_INLINE
> +# include <asm/irq_stack.h>
> +#endif
> +
>  #define CREATE_TRACE_POINTS
>  #include <trace/events/irq.h>
>
>