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()
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Date: Mon, 14 Aug 2017 17:52:25 +0000
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On Mon, 2017-08-14 at 19:05 +0200, Borislav Petkov wrote:
> On Mon, Aug 14, 2017 at 04:48:57PM +0000, Kani, Toshimitsu wrote:
> > Right, but the issue is how [ghes_edac_]report_mem_error() protects
> > from possible concurrent calls from multiple GHES sources when
> > there is only a single mci.
> 
> Do you know of an actual firmware reporting multiple errors
> concurrently?

I do not know.  We have multiple GHES entries, but they all use SCI. 
Since ACPICA uses a single threaded workqueue for notify handlers, they
are serialized among SCIs.

ACPI 6.2 defines multiple notification types in Table 18-383, and
ghes_proc() can be called from ghes_poll_func(), ghes_irq_func(), and
ghes_notify_sci().  So, I think it is safe to operate per an entry
basis.

> GHES v2 even needs to ACK the current error first before it can read
> the next one.

Yes, but this ACK is done per a GHES entry as well.

Thanks,
-Toshi