linux-kernel - Re: [PATCH 4/6] x86-mce: Add spinlocks to prevent duplicated MCP and CMCI reports.

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Message-ID: <20140710184416.GE5603@pd.tnic>
Date:	Thu, 10 Jul 2014 20:44:16 +0200
From:	Borislav Petkov <bp@...en8.de>
To:	Havard Skinnemoen <hskinnemoen@...gle.com>
Cc:	Tony Luck <tony.luck@...el.com>,
	Linux Kernel <linux-kernel@...r.kernel.org>,
	Ewout van Bekkum <ewout@...gle.com>
Subject: Re: [PATCH 4/6] x86-mce: Add spinlocks to prevent duplicated MCP and
 CMCI reports.

On Thu, Jul 10, 2014 at 11:03:43AM -0700, Havard Skinnemoen wrote:
> For non-shared banks, we might risk some CPUs not being able to
> poll their banks in a long time if they happen to be more or less
> synchronized with a different CPU. This will also get worse with
> shorter polling intervals, and with larger numbers of CPUs.

No, I meant to do something like

	if (atomic_dec_and_test(&mce_banks[i].poll))
		m.status = mce_rdmsrl(MSR_IA32_MCx_STATUS(i));

	atomic_add_unless(&mce_banks[i].poll, 1, 1);

so that you have only one CPU read the status register of mce_banks[i].

For non-shared banks, this will always work because no other CPU will
dec that variable anyway.

Or am I missing something...?

-- 
Regards/Gruss,
    Boris.

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