linux-kernel - Re: [PATCH v3 4/9] ACPI, x86: Extended error log driver for x86 platform

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Message-ID: <20140627092227.GA23153@pd.tnic>
Date:	Fri, 27 Jun 2014 11:22:27 +0200
From:	Borislav Petkov <bp@...en8.de>
To:	Xie XiuQi <xiexiuqi@...wei.com>
Cc:	"Naveen N. Rao" <naveen.n.rao@...ux.vnet.ibm.com>,
	"Chen, Gong" <gong.chen@...ux.intel.com>, tony.luck@...el.com,
	joe@...ches.com, m.chehab@...sung.com, arozansk@...hat.com,
	linux-acpi@...r.kernel.org, linux-kernel@...r.kernel.org,
	Li Bin <huawei.libin@...wei.com>
Subject: Re: [PATCH v3 4/9] ACPI, x86: Extended error log driver for x86
 platform

On Fri, Jun 27, 2014 at 01:34:45PM +0800, Xie XiuQi wrote:
> The call graph is like this,
> do_machine_check
>  -> mce_log
>   -> atomic_notifier_call_chain(&x86_mce_decoder_chain ...)
>    -> ...
>     -> extlog_print
>      -> print_extlog_rcd
>       -> __print_extlog_rcd
>        -> printk
> 
> There's a logbuf_lock in printk. If logbuf_lock is held by other cpu,
> it'll lead to an infinity spin here. Isn't it?

Yes, but we want to take the risk and print something out before the
machine dies instead of waiting to get into printk-safe context first
and maybe corrupt state.

Besides, there's work currently going on to make printk safe in atomic
context so...

-- 
Regards/Gruss,
    Boris.

Sent from a fat crate under my desk. Formatting is fine.
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