From: "Kani, Toshimitsu" <toshi.kani@hpe.com>
To: "bp@alien8.de" <bp@alien8.de>
CC: "linux-acpi@vger.kernel.org" <linux-acpi@vger.kernel.org>,
        "lenb@kernel.org" <lenb@kernel.org>,
        "mchehab@kernel.org" <mchehab@kernel.org>,
        "tony.luck@intel.com" <tony.luck@intel.com>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        "linux-edac@vger.kernel.org" <linux-edac@vger.kernel.org>,
        "rjw@rjwysocki.net" <rjw@rjwysocki.net>
Subject: Re: [PATCH v2 4/7] ghes_edac: avoid multiple calls to dmi_walk()
Thread-Topic: [PATCH v2 4/7] ghes_edac: avoid multiple calls to dmi_walk()
Thread-Index: AQHTDKTuWyxK/OMe00e0Ovda8CeGBqJzlIKAgAEZcQCAAIyugIAD9yeA
Date: Mon, 7 Aug 2017 17:59:15 +0000
Message-ID: <1502128177.2042.131.camel@hpe.com>
References: <20170803215753.30553-1-toshi.kani@hpe.com>
         <20170803215753.30553-5-toshi.kani@hpe.com>
         <20170804040525.GE12082@nazgul.tnic> <1501879964.2042.117.camel@hpe.com>
         <20170805051615.GC23214@nazgul.tnic>
In-Reply-To: <20170805051615.GC23214@nazgul.tnic>
Accept-Language: en-US
Content-Language: en-US
spamdiagnosticoutput: 1:99
spamdiagnosticmetadata: NSPM
Content-Type: text/plain; charset="utf-8"
Content-ID: <260B6D54D552984C9453CA3D41346493@NAMPRD84.PROD.OUTLOOK.COM>
MIME-Version: 1.0
X-MS-Exchange-CrossTenant-originalarrivaltime: 07 Aug 2017 17:59:15.3444
 (UTC)
X-MS-Exchange-CrossTenant-fromentityheader: Hosted
X-MS-Exchange-CrossTenant-id: 105b2061-b669-4b31-92ac-24d304d195dc
X-MS-Exchange-Transport-CrossTenantHeadersStamped: DF4PR84MB0186
X-OriginatorOrg: hpe.com
Sender: linux-kernel-owner@vger.kernel.org
List-ID: <linux-kernel.vger.kernel.org>
X-Mailing-List: linux-kernel@vger.kernel.org
Content-Transfer-Encoding: 8bit
X-MIME-Autoconverted: from base64 to 8bit by nfs id v77HxRqa025264
Content-Length: 1491
Lines: 38

On Sat, 2017-08-05 at 07:16 +0200, Borislav Petkov wrote:
> On Fri, Aug 04, 2017 at 09:02:17PM +0000, Kani, Toshimitsu wrote:
> > GHES platform devices correspond to GHES entries, which define
> > firmware interfaces to report generic memory errors to the OS, such
> > as NMI and SCI.  These devices are associated with all DIMMs, not a
> > particular DIMM.
> 
> And? Stating the obvious brings you what exactly?
> 
> IOW, you still haven't answered my question.

Sorry about that.  Let me copy your original comments to make sure I
answer your questions this time.

> So the problem is that ghes_edac_register() gets called multiple
> times depending on how many GHES platform devices are on the system.
> But yet they all scan *all* DIMMs. 

Right, and this patch changes ghes_edac_register() to scan all DIMMs at
the first time and do not scan them next times.

> So instead you should return if
> the DIMMs have been counted already and not register a second time.
> Which makes that whole mc counting kinda useless. So you could rip
>
that out too.

Oh, I see.  So, ghes_edac_register() should return no-op a second time,
and does not call edac_mc_add_mc() to register with a separate mci.

I think we should keep the current scheme, which registers an mci for
each GHES entry.  ghes_edac_report_mem_error() expects that error-
reporting is serialized per a GHES entry.  Sharing a single mci among
all GHES entries / error interfaces might lead to a race condition.

Thanks,
-Toshi