linux-kernel - Re: pci-ftpci100: race condition in masking/unmasking interrupts

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Message-ID: <CACRpkdYe-Y-1YstovrJd7b8iNCDeX312mB4gLGcG1y6dE6di=A@mail.gmail.com>
Date:   Tue, 7 Sep 2021 13:22:37 +0200
From:   Linus Walleij <linus.walleij@...aro.org>
To:     Pali Rohár <pali@...nel.org>
Cc:     Lorenzo Pieralisi <lorenzo.pieralisi@....com>,
        Rob Herring <robh@...nel.org>, Marc Zyngier <maz@...nel.org>,
        linux-pci <linux-pci@...r.kernel.org>,
        linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: pci-ftpci100: race condition in masking/unmasking interrupts

On Wed, Aug 18, 2021 at 1:47 PM Pali Rohár <pali@...nel.org> wrote:

> I do not see any entry in MAINTAINERS file for pci-ftpci100.c driver, so
> I'm not sure to whom should I address this issue...

It's me.

> During pci-aardvark review, Marc pointed one issue which is currently
> available also in pci-ftpci100.c driver.
>
> When masking or unmasking interrupts there is read-modify-write sequence
> for FARADAY_PCI_CTRL2 register without any locking and is not atomic:
>
> https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/drivers/pci/controller/pci-ftpci100.c?h=v5.13#n270
>
> So there is race condition when masking/unmasking more interrupts at the
> same time.

I thought those operations were called in atomic context.
How did you fix it?

Yours,
Linus Walleij