linux-kernel - Re: [REGRESSION] Re: [patch V3 09/33] genirq/msi: Add range checking to msi_insert

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Message-ID: <Y/PHN+0nETV3o1pQ@shell.armlinux.org.uk>
Date:   Mon, 20 Feb 2023 19:17:11 +0000
From:   "Russell King (Oracle)" <linux@...linux.org.uk>
To:     Marc Zyngier <maz@...nel.org>, Andrew Lunn <andrew@...n.ch>
Cc:     Thomas Gleixner <tglx@...utronix.de>,
        LKML <linux-kernel@...r.kernel.org>, x86@...nel.org,
        Joerg Roedel <joro@...tes.org>, Will Deacon <will@...nel.org>,
        linux-pci@...r.kernel.org, Bjorn Helgaas <bhelgaas@...gle.com>,
        Lorenzo Pieralisi <lorenzo.pieralisi@....com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Jason Gunthorpe <jgg@...lanox.com>,
        Dave Jiang <dave.jiang@...el.com>,
        Alex Williamson <alex.williamson@...hat.com>,
        Kevin Tian <kevin.tian@...el.com>,
        Dan Williams <dan.j.williams@...el.com>,
        Logan Gunthorpe <logang@...tatee.com>,
        Ashok Raj <ashok.raj@...el.com>, Jon Mason <jdmason@...zu.us>,
        Allen Hubbe <allenbh@...il.com>
Subject: Re: [REGRESSION] Re: [patch V3 09/33] genirq/msi: Add range checking
 to msi_insert_desc()

On Mon, Feb 20, 2023 at 06:29:33PM +0000, Marc Zyngier wrote:
> Lockdep also reports[1] a possible circular locking dependency between
> phy_attach_direct() and rtnetlink_rcv_msg(), which looks interesting.
> 
> [1] https://paste.debian.net/1271454/

Adding Andrew, but really this should be in a separate thread, since
this has nothing to do with MSI.

It looks like the open path takes the RTNL lock followed by the phydev
lock, whereas the PHY probe path takes the phydev lock, and then if
there's a SFP attached to the PHY, we end up taking the RTNL lock.
That's going to be utterly horrid to try and solve, and isn't going
to be quick to fix.

-- 
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