linux-kernel - Re: [PATCH -v2] x86: MCE: Re-implement MCE log ring buffer as per-CPU ring buffer

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Date:	Tue, 28 Apr 2009 12:21:25 +0200
From:	Andi Kleen <andi@...stfloor.org>
To:	Huang Ying <ying.huang@...el.com>
Cc:	Ingo Molnar <mingo@...e.hu>, "H. Peter Anvin" <hpa@...or.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Andi Kleen <ak@...ux.intel.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH -v2] x86: MCE: Re-implement MCE log ring buffer as per-CPU ring buffer

Huang Ying <ying.huang@...el.com> writes:
>
> ChangeLog:
>
> v2:
>
> - Use alloc_percpu() to allocate per_cpu mcelog buffer

Sorry, why didn't you just use DEFINE_PER_CPU ? That should work
as well and will be shorter.

Another thing I noticed. the "MACHINECHECK" signature was originally
for crash dump tools to find the log. If you change the format
you should change it to MACHINECHEC2 or so.

> +	size_t usize_limit;
> +
> +	/* Too large user buffer size may cause system not response */
> +	usize_limit = num_possible_cpus() * MCE_LOG_LEN * sizeof(struct mce);
> +	if (usize > usize_limit)
> +		usize = usize_limit;

Did you ever track down what happens here? I still find it worrying

Otherwise looks good.

-Andi

-- 
ak@...ux.intel.com -- Speaking for myself only.
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