linux-kernel - Re: [PATCH 1/2] Revert "PCI/IOV: Add PCI rescan-remove locking when enabling/disabling SR-IOV"

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Message-ID: <20251107105439.GF20064@p1gen4-pw042f0m.boeblingen.de.ibm.com>
Date: Fri, 7 Nov 2025 11:54:39 +0100
From: Benjamin Block <bblock@...ux.ibm.com>
To: Niklas Schnelle <schnelle@...ux.ibm.com>
Cc: Bjorn Helgaas <helgaas@...nel.org>, Lukas Wunner <lukas@...ner.de>,
        Keith Busch <kbusch@...nel.org>, Gerd Bayer <gbayer@...ux.ibm.com>,
        Matthew Rosato <mjrosato@...ux.ibm.com>,
        Halil Pasic <pasic@...ux.ibm.com>, Farhan Ali <alifm@...ux.ibm.com>,
        Julian Ruess <julianr@...ux.ibm.com>,
        Heiko Carstens <hca@...ux.ibm.com>, Vasily Gorbik <gor@...ux.ibm.com>,
        Alexander Gordeev <agordeev@...ux.ibm.com>, linux-pci@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/2] Revert "PCI/IOV: Add PCI rescan-remove locking when
 enabling/disabling SR-IOV"

On Thu, Oct 30, 2025 at 11:26:01AM +0100, Niklas Schnelle wrote:
> This reverts commit 05703271c3cd ("PCI/IOV: Add PCI rescan-remove
> locking when enabling/disabling SR-IOV") which causes a deadlock by
> recursively taking pci_rescan_remove_lock when sriov_del_vfs() is called
> as part of pci_stop_and_remove_bus_device(). For example with the
> following sequence of commands:
> 
> $ echo <NUM> > /sys/bus/pci/devices/<pf>/sriov_numvfs
> $ echo 1 > /sys/bus/pci/devices/<pf>/remove
> 
> A trimmed trace of the deadlock on a mlx5 device is as below:
> 
>  mutex_lock_nested+0x3c/0x50
>  sriov_disable+0x34/0x140
>  mlx5_sriov_disable+0x50/0x80 [mlx5_core]
>  remove_one+0x5e/0xf0 [mlx5_core]
>  pci_device_remove+0x3c/0xa0
>  device_release_driver_internal+0x18e/0x280
>  pci_stop_bus_device+0x82/0xa0
>  pci_stop_and_remove_bus_device_locked+0x5e/0x80
>  remove_store+0x72/0x90
> 
> This is not a complete fix as it restores the issue the cited commit
> tried to solve.
> 

Reviewed-by: Benjamin Block <bblock@...ux.ibm.com>

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