linux-kernel - Re: [PATCH 19/31] x86: MCE: Default to panic timeout for machine checks v2

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Message-ID: <4A1CC20B.1020907@jp.fujitsu.com>
Date:	Wed, 27 May 2009 13:31:07 +0900
From:	Hidetoshi Seto <seto.hidetoshi@...fujitsu.com>
To:	Andi Kleen <andi@...stfloor.org>
CC:	linux-kernel@...r.kernel.org, hpa@...or.com, x86@...nel.org,
	Andi Kleen <ak@...ux.intel.com>
Subject: Re: [PATCH 19/31] x86: MCE: Default to panic timeout for machine
 checks v2

Andi Kleen wrote:
> From: Andi Kleen <ak@...ux.intel.com>
> 
> Fatal machine checks can be logged to disk after boot, but only if
> the system did a warm reboot. That's unfortunately difficult with the
> default panic behaviour, which waits forever and the admin has to
> press the power button because modern systems usually miss a reset button.
> This clears the machine checks in the registers and make
> it impossible to log them.
> 
> This patch changes the default for machine check panic to always
> reboot after 30s. Then the mce can be successfully logged after
> reboot.
> 
> I believe this will improve machine check experience for any
> system running the X server.
> 
> This is dependent on successfull boot logging of MCEs. This currently
> only works on Intel systems, on AMD there are quite a lot of systems
> around which leave junk in the machine check registers after boot,
> so it's disabled here. These systems will continue to default
> to endless waiting panic.
> 
> v2: Only force panic timeout when it's shorter (H.Seto)
> 
> Signed-off-by: Andi Kleen <ak@...ux.intel.com>
> ---

I suppose the original intention is overwrite the panic_timeout 0 to 30.

> @@ -240,6 +243,8 @@ static void mce_panic(char *msg, struct mce *final, char *exp)
>  		printk(KERN_EMERG "Some CPUs didn't answer in synchronization\n");
>  	if (exp)
>  		printk(KERN_EMERG "Machine check: %s\n", exp);
> +	if (mce_panic_timeout < panic_timeout)
> +		panic_timeout = mce_panic_timeout;
>  	panic(msg);
>  }
>  
> @@ -1100,6 +1105,8 @@ static void mce_cpu_quirks(struct cpuinfo_x86 *c)
>  	}
>  	if (monarch_timeout < 0)
>  		monarch_timeout = 0;
> +	if (mce_bootlog != 0)
> +		mce_panic_timeout = 30;
>  }
>  
>  static void __cpuinit mce_ancient_init(struct cpuinfo_x86 *c)

It seems it doesn't work.

I made a incremental patch for this fix.  Please consider applying.


Thanks,
H.Seto

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