linux-kernel - Re: [PATCH] PCI: pciehp: fix circular lock dependency b/w pci_rescan_remove_lock and reset

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Message-ID: <aFQ4ncPNdmUgyw63@wunner.de>
Date: Thu, 19 Jun 2025 18:19:41 +0200
From: Lukas Wunner <lukas@...ner.de>
To: Raju Rangoju <Raju.Rangoju@....com>
Cc: bhelgaas@...gle.com, linux-pci@...r.kernel.org,
	linux-kernel@...r.kernel.org, Sanath S <Sanath.S@....com>
Subject: Re: [PATCH] PCI: pciehp: fix circular lock dependency b/w
 pci_rescan_remove_lock and reset_lock

On Thu, Jun 19, 2025 at 09:16:10PM +0530, Raju Rangoju wrote:
> Resolves a circular locking dependency issue between
> pci_rescan_remove_lock() and ctrl->reset_lock() in the PCI hotplug
> subsystem, specifically in the pciehp_unconfigure_device() function.

This seems to be a false-positive because the two stacktraces are identical
but pciehp_ist() is single-threaded.  There is only ever a single instance
of pciehp_ist() running per hotplug port, so two instances running on
separate CPUs can never happen.

Previous reports of the same false-positive lockdep splat, only they
refer to pciehp_configure_device() instead of pciehp_unconfigure_device():

https://lore.kernel.org/r/20231015093722.GA11283@wunner.de/
https://lore.kernel.org/r/ZzJm6QrQyT48jGuN@wunner.de/

Thanks,

Lukas