linux-kernel - Re: [PATCH 2/3] x86/mce/AMD: Define a list_head for threshold blocks outside the list

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Message-ID: <20170530135633.y2hbkpc2ak3zkgtw@pd.tnic>
Date:   Tue, 30 May 2017 15:56:33 +0200
From:   Borislav Petkov <bp@...en8.de>
To:     "Ghannam, Yazen" <Yazen.Ghannam@....com>
Cc:     "linux-edac@...r.kernel.org" <linux-edac@...r.kernel.org>,
        Tony Luck <tony.luck@...el.com>,
        "x86@...nel.org" <x86@...nel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 2/3] x86/mce/AMD: Define a list_head for threshold blocks
 outside the list

On Tue, May 30, 2017 at 12:39:03PM +0000, Ghannam, Yazen wrote:
> Like I said in the commit message, the list_head needs to be outside the
> list to access all the elements using list_for_each*. Otherwise, we won't
> get a reference to the "head" element since we iterate starting from
> head->next and break when !head.

I believe the whole hierarchy here is done a bit differently: the list
starts at threshold_bank->blocks which points to the first threshold
block. So when iterating, you need to look at threshold_bank->blocks
first, which is the first element and then traverse the list.

This is basically how the list gets built:

allocate_threshold_blocks:

	...

        if (per_cpu(threshold_banks, cpu)[bank]->blocks)
                list_add(&b->miscj, &per_cpu(threshold_banks, cpu)[bank]->blocks->miscj);
        else
                per_cpu(threshold_banks, cpu)[bank]->blocks = b;

per_cpu(threshold_banks, cpu)[bank]->blocks is the first element as
it points to a struct threshold_block and then the ..->blocks->miscj
contains any further threshold blocks present on this bank and we queue
them there if ->blocks is not NULL.

HTH.

-- 
Regards/Gruss,
    Boris.

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