linux-kernel - Re: [RFC PATCH 2/3] ARM: entry: Remove unneeded need

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Message-ID: <fa090a80-5579-5dac-da19-56c9a6c5c423@arm.com>
Date:   Fri, 1 Feb 2019 08:49:37 +0000
From:   Julien Thierry <julien.thierry@....com>
To:     Valentin Schneider <valentin.schneider@....com>,
        linux-kernel@...r.kernel.org
Cc:     Russell King <linux@...linux.org.uk>,
        Thomas Gleixner <tglx@...utronix.de>,
        Will Deacon <will.deacon@....com>,
        linux-arm-kernel@...ts.infradead.org
Subject: Re: [RFC PATCH 2/3] ARM: entry: Remove unneeded need_resched() loop

Hi Valentin,

On 31/01/2019 18:23, Valentin Schneider wrote:
> Since the enabling and disabling of IRQs within preempt_schedule_irq()
> is contained in a need_resched() loop, we don't need the outer arch
> code loop.
> 
> Signed-off-by: Valentin Schneider <valentin.schneider@....com>
> Cc: Russell King <linux@...linux.org.uk>
> Cc: Thomas Gleixner <tglx@...utronix.de>
> Cc: Will Deacon <will.deacon@....com>
> Cc: Julien Thierry <julien.thierry@....com>
> Cc: linux-arm-kernel@...ts.infradead.org

Reviewed-by: Julien Thierry <julien.thierry@....com>

Cheers,

> ---
>  arch/arm/kernel/entry-armv.S | 12 +-----------
>  1 file changed, 1 insertion(+), 11 deletions(-)
> 
> diff --git a/arch/arm/kernel/entry-armv.S b/arch/arm/kernel/entry-armv.S
> index e85a3af9ddeb..a7ac22e09bb2 100644
> --- a/arch/arm/kernel/entry-armv.S
> +++ b/arch/arm/kernel/entry-armv.S
> @@ -220,7 +220,7 @@ __irq_svc:
>  	teq	r8, #0				@ if preempt count != 0
>  	movne	r0, #0				@ force flags to 0
>  	tst	r0, #_TIF_NEED_RESCHED
> -	blne	svc_preempt
> +	blne	preempt_schedule_irq            @ irq en/disable is done inside
>  #endif
>  
>  	svc_exit r5, irq = 1			@ return from exception
> @@ -229,16 +229,6 @@ ENDPROC(__irq_svc)
>  
>  	.ltorg
>  
> -#ifdef CONFIG_PREEMPT
> -svc_preempt:
> -	mov	r8, lr
> -1:	bl	preempt_schedule_irq		@ irq en/disable is done inside
> -	ldr	r0, [tsk, #TI_FLAGS]		@ get new tasks TI_FLAGS
> -	tst	r0, #_TIF_NEED_RESCHED
> -	reteq	r8				@ go again
> -	b	1b
> -#endif
> -
>  __und_fault:
>  	@ Correct the PC such that it is pointing at the instruction
>  	@ which caused the fault.  If the faulting instruction was ARM
> 

-- 
Julien Thierry