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Subject: Re: [PATCH 03/34] powerpc: Use CONFIG_PREEMPTION
To:     Sebastian Andrzej Siewior <bigeasy@linutronix.de>,
        linux-kernel@vger.kernel.org
Cc:     Paul Mackerras <paulus@samba.org>, tglx@linutronix.de,
        linuxppc-dev@lists.ozlabs.org
References: <20191015191821.11479-1-bigeasy@linutronix.de>
 <20191015191821.11479-4-bigeasy@linutronix.de>
From:   Christophe Leroy <christophe.leroy@c-s.fr>
Message-ID: <156db456-af80-1f5e-6234-2e78283569b6@c-s.fr>
Date:   Wed, 16 Oct 2019 06:57:48 +0200
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Le 15/10/2019 à 21:17, Sebastian Andrzej Siewior a écrit :
> From: Thomas Gleixner <tglx@linutronix.de>
> 
> CONFIG_PREEMPTION is selected by CONFIG_PREEMPT and by CONFIG_PREEMPT_RT.
> Both PREEMPT and PREEMPT_RT require the same functionality which today
> depends on CONFIG_PREEMPT.
> 
> Switch the entry code over to use CONFIG_PREEMPTION. Add PREEMPT_RT
> output in __die().

powerpc doesn't select ARCH_SUPPORTS_RT, so this change is useless as 
CONFIG_PREEMPT_RT cannot be selected.

> 
> Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
> Cc: Paul Mackerras <paulus@samba.org>
> Cc: Michael Ellerman <mpe@ellerman.id.au>
> Cc: linuxppc-dev@lists.ozlabs.org
> Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
> [bigeasy: +traps.c, Kconfig]
> Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
> ---
>   arch/powerpc/Kconfig           | 2 +-
>   arch/powerpc/kernel/entry_32.S | 4 ++--
>   arch/powerpc/kernel/entry_64.S | 4 ++--
>   arch/powerpc/kernel/traps.c    | 7 ++++++-
>   4 files changed, 11 insertions(+), 6 deletions(-)
> 
> diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig
> index 3e56c9c2f16ee..8ead8d6e1cbc8 100644
> --- a/arch/powerpc/Kconfig
> +++ b/arch/powerpc/Kconfig
> @@ -106,7 +106,7 @@ config LOCKDEP_SUPPORT
>   config GENERIC_LOCKBREAK
>   	bool
>   	default y
> -	depends on SMP && PREEMPT
> +	depends on SMP && PREEMPTION
>   
>   config GENERIC_HWEIGHT
>   	bool
> diff --git a/arch/powerpc/kernel/entry_32.S b/arch/powerpc/kernel/entry_32.S
> index d60908ea37fb9..e1a4c39b83b86 100644
> --- a/arch/powerpc/kernel/entry_32.S
> +++ b/arch/powerpc/kernel/entry_32.S
> @@ -897,7 +897,7 @@ user_exc_return:		/* r10 contains MSR_KERNEL here */
>   	bne-	0b
>   1:
>   
> -#ifdef CONFIG_PREEMPT
> +#ifdef CONFIG_PREEMPTION
>   	/* check current_thread_info->preempt_count */
>   	lwz	r0,TI_PREEMPT(r2)
>   	cmpwi	0,r0,0		/* if non-zero, just restore regs and return */
> @@ -921,7 +921,7 @@ user_exc_return:		/* r10 contains MSR_KERNEL here */
>   	 */
>   	bl	trace_hardirqs_on
>   #endif
> -#endif /* CONFIG_PREEMPT */
> +#endif /* CONFIG_PREEMPTION */
>   restore_kuap:
>   	kuap_restore r1, r2, r9, r10, r0
>   
> diff --git a/arch/powerpc/kernel/entry_64.S b/arch/powerpc/kernel/entry_64.S
> index 6467bdab8d405..83733376533e8 100644
> --- a/arch/powerpc/kernel/entry_64.S
> +++ b/arch/powerpc/kernel/entry_64.S
> @@ -840,7 +840,7 @@ _GLOBAL(ret_from_except_lite)
>   	bne-	0b
>   1:
>   
> -#ifdef CONFIG_PREEMPT
> +#ifdef CONFIG_PREEMPTION
>   	/* Check if we need to preempt */
>   	andi.	r0,r4,_TIF_NEED_RESCHED
>   	beq+	restore
> @@ -871,7 +871,7 @@ _GLOBAL(ret_from_except_lite)
>   	li	r10,MSR_RI
>   	mtmsrd	r10,1		  /* Update machine state */
>   #endif /* CONFIG_PPC_BOOK3E */
> -#endif /* CONFIG_PREEMPT */
> +#endif /* CONFIG_PREEMPTION */
>   
>   	.globl	fast_exc_return_irq
>   fast_exc_return_irq:
> diff --git a/arch/powerpc/kernel/traps.c b/arch/powerpc/kernel/traps.c
> index 82f43535e6867..23d2f20be4f2e 100644
> --- a/arch/powerpc/kernel/traps.c
> +++ b/arch/powerpc/kernel/traps.c
> @@ -252,14 +252,19 @@ NOKPROBE_SYMBOL(oops_end);
>   
>   static int __die(const char *str, struct pt_regs *regs, long err)
>   {
> +	const char *pr = "";
> +

Please follow the same approach as already existing. Don't add a local 
var for that.

>   	printk("Oops: %s, sig: %ld [#%d]\n", str, err, ++die_counter);
>   
> +	if (IS_ENABLED(CONFIG_PREEMPTION))
> +		pr = IS_ENABLED(CONFIG_PREEMPT_RT) ? " PREEMPT_RT" : " PREEMPT";
> +

drop

>   	printk("%s PAGE_SIZE=%luK%s%s%s%s%s%s%s %s\n",

Add one %s

>   	       IS_ENABLED(CONFIG_CPU_LITTLE_ENDIAN) ? "LE" : "BE",
>   	       PAGE_SIZE / 1024,
>   	       early_radix_enabled() ? " MMU=Radix" : "",
>   	       early_mmu_has_feature(MMU_FTR_HPTE_TABLE) ? " MMU=Hash" : "",
> -	       IS_ENABLED(CONFIG_PREEMPT) ? " PREEMPT" : "",

Replace by: 	IS_ENABLED(CONFIG_PREEMPTION) ? " PREEMPT" : ""

> +	       pr,

add something like: IS_ENABLED(CONFIG_PREEMPT_RT) ? "_RT" : ""

>   	       IS_ENABLED(CONFIG_SMP) ? " SMP" : "",
>   	       IS_ENABLED(CONFIG_SMP) ? (" NR_CPUS=" __stringify(NR_CPUS)) : "",
>   	       debug_pagealloc_enabled() ? " DEBUG_PAGEALLOC" : "",
> 

Christophe