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

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Date:   Wed, 18 Aug 2021 13:47:43 +0200
From:   Pali Rohár <pali@...nel.org>
To:     Linus Walleij <linus.walleij@...aro.org>,
        Lorenzo Pieralisi <lorenzo.pieralisi@....com>,
        Rob Herring <robh@...nel.org>
Cc:     Marc Zyngier <maz@...nel.org>, linux-pci@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: pci-ftpci100: race condition in masking/unmasking interrupts

Hello!

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...

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.