linux-kernel - Re: [PATCH] x86/mce: Fix initialization error warning

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Date:   Mon, 16 Jan 2017 22:56:06 +0100 (CET)
From:   Thomas Gleixner <tglx@...utronix.de>
To:     Prarit Bhargava <prarit@...hat.com>
cc:     linux-kernel@...r.kernel.org, Tony Luck <tony.luck@...el.com>,
        Borislav Petkov <bp@...en8.de>, Ingo Molnar <mingo@...hat.com>,
        "H. Peter Anvin" <hpa@...or.com>, x86@...nel.org,
        linux-edac@...r.kernel.org
Subject: Re: [PATCH] x86/mce: Fix initialization error warning

On Mon, 16 Jan 2017, Prarit Bhargava wrote:
> When booting kernel with mce=off a loud warning from the mce code
> is displayed.  This causes confusion for end users.
> 
> Add a check to see if MCE is available before outputting the warning
> message.

Sigh.

> Signed-off-by: Prarit Bhargava <prarit@...hat.com>
> Cc: Tony Luck <tony.luck@...el.com>
> Cc: Borislav Petkov <bp@...en8.de>
> Cc: Thomas Gleixner <tglx@...utronix.de>
> Cc: Ingo Molnar <mingo@...hat.com>
> Cc: "H. Peter Anvin" <hpa@...or.com>
> Cc: x86@...nel.org
> Cc: linux-edac@...r.kernel.org
> ---
>  arch/x86/kernel/cpu/mcheck/mce.c |    3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/arch/x86/kernel/cpu/mcheck/mce.c b/arch/x86/kernel/cpu/mcheck/mce.c
> index 00ef43233e03..943a0c440c55 100644
> --- a/arch/x86/kernel/cpu/mcheck/mce.c
> +++ b/arch/x86/kernel/cpu/mcheck/mce.c
> @@ -2662,7 +2662,8 @@ static __init int mcheck_init_device(void)
>  	free_cpumask_var(mce_device_initialized);
>  
>  err_out:
> -	pr_err("Unable to init device /dev/mcelog (rc: %d)\n", err);
> +	if (mce_available(&boot_cpu_data))
> +		pr_err("Unable to init device /dev/mcelog (rc: %d)\n", err);

This is really crap. Why would you check the same condition twice? Just
because it's so much more complicated than doing the obvious:

--- a/arch/x86/kernel/cpu/mcheck/mce.c
+++ b/arch/x86/kernel/cpu/mcheck/mce.c
@@ -2615,10 +2615,8 @@ static __init int mcheck_init_device(voi
 	enum cpuhp_state hp_online;
 	int err;
 
-	if (!mce_available(&boot_cpu_data)) {
-		err = -EIO;
-		goto err_out;
-	}
+	if (!mce_available(&boot_cpu_data))
+		return -EIO;
 
 	if (!zalloc_cpumask_var(&mce_device_initialized, GFP_KERNEL)) {
 		err = -ENOMEM;