Hi,

On 1/11/21 7:39 PM, Kaneda, Erik wrote:

quoted

-----Original Message-----
From: Hans de Goede <redacted>
Sent: Saturday, December 26, 2020 6:28 AM
To: Rafael J . Wysocki <redacted>; Len Brown <lenb@kernel.org>;
Moore, Robert [off-list ref]; Kaneda, Erik
[off-list ref]
Cc: Hans de Goede <redacted>; linux-acpi@vger.kernel.org;
devel@acpica.org
Subject: [PATCH 0/2] ACPICA: Fix a race in GenericSerialBus (I2C) and GPIO
handling

Hi All,

On one of my machines I noticed the following errors being logged:

[   52.892807] i2c i2c-0: adapter quirk: no zero length (addr 0x0078, size 0,
read)
[   52.893037] i2c i2c-0: i2c read 0 bytes from client@0x78 starting at reg 0x0
failed, error: -95

The second line is coming from the Linux I2C ACPI OpRegion handling and
after a bunch of debugging I've found out that there is a rather obvious
(once you see it) and nasty race condition in the handling of I2C and GPIO
opregions in acpi_ev_address_space_dispatch(). See the first patch in this
series (the second patch is a follow-up cleanup patch removing some code
duplication).

TBH I'm surprised that this issue has gone unnoticed as long as it has,
but I guess that it mostly leads to unreproducable sporadic problems
making it hard to debug and I got lucky that I had a machine where the
race seems to trigger about once every 20 seconds.

I know that ACPICA patches are normally merged through the ACPICA
upstream
but given that this is a serious bug, I believe that in this case it might
be best to add the fix directly to Linux and then port it to ACPICA from
there.

Thanks for this changeset! I'm taking a look right now

Ok, note I already ported it to ACPICA git and submitted a pull-req
(on Bob's request): https://github.com/acpica/acpica/pull/658

Regards,

Hans