linux-kernel - Re: [PATCH v4] PCI: vmd: Make vmd_dev::cfg_lock a raw_spinlock

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Message-ID: <20250221011754.GE2510987@rocinante>
Date: Fri, 21 Feb 2025 10:17:54 +0900
From: Krzysztof Wilczyński <kw@...ux.com>
To: Bjorn Helgaas <helgaas@...nel.org>
Cc: Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
	linux-pci@...r.kernel.org,
	"Luis Claudio R. Goncalves" <lgoncalv@...hat.com>,
	Ryo Takakura <ryotkkr98@...il.com>, bhelgaas@...gle.com,
	jonathan.derrick@...ux.dev, lpieralisi@...nel.org,
	manivannan.sadhasivam@...aro.org, nirmal.patel@...ux.intel.com,
	robh@...nel.org, rostedt@...dmis.org, kbusch@...nel.org,
	linux-kernel@...r.kernel.org, linux-rt-devel@...ts.linux.dev
Subject: Re: [PATCH v4] PCI: vmd: Make vmd_dev::cfg_lock a raw_spinlock_t.

Hello,

> > The access to the PCI config space via pci_ops::read and pci_ops::write
> > is a low-level hardware access. The functions can be accessed with
> > disabled interrupts even on PREEMPT_RT. The pci_lock has been made a
> > raw_spinlock_t for this purpose. A spinlock_t becomes a sleeping lock on
> > PREEMPT_RT can not be acquired with disabled interrupts.
> 
> I think this is missing a word or two and should say:
> 
>   A spinlock_t becomes a sleeping lock on PREEMPT_RT, so it cannot be
>   acquired with disabled interrupts.

I changed the commit log directly on the relevant branch.  Thank you!

	Krzysztof