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PCI/IOV: Fix SR-IOV locking races and AB-BA deadlock From: Niklas Schnelle To: "Ionut Nechita (Wind River)" , linux-pci@vger.kernel.org, bhelgaas@google.com Cc: helgaas@kernel.org, sebott@linux.ibm.com, bblock@linux.ibm.com, lkml@mageta.org, alifm@linux.ibm.com, julianr@linux.ibm.com, dtatulea@nvidia.com, mani@kernel.org, lukas@wunner.de, kbusch@kernel.org, linux@roeck-us.net, ionut_n2001@yahoo.com, sunlightlinux@gmail.com, linux-kernel@vger.kernel.org, stable@vger.kernel.org, intel-xe@lists.freedesktop.org, matthew.brost@intel.com, michal.wajdeczko@intel.com, piotr.piorkowski@intel.com In-Reply-To: <20260318210316.61975-1-ionut.nechita@windriver.com> References: <20260318210316.61975-1-ionut.nechita@windriver.com> Autocrypt: addr=schnelle@linux.ibm.com; prefer-encrypt=mutual; keydata=mQINBGHm3M8BEAC+MIQkfoPIAKdjjk84OSQ8erd2OICj98+GdhMQpIjHXn/RJdCZLa58k /ay5x0xIHkWzx1JJOm4Lki7WEzRbYDexQEJP0xUia0U+4Yg7PJL4Dg/W4Ho28dRBROoJjgJSLSHwc 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priorityscore=1501 suspectscore=0 bulkscore=0 spamscore=0 impostorscore=0 malwarescore=0 adultscore=0 clxscore=1011 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.22.0-2603050001 definitions=main-2603190098 On Wed, 2026-03-18 at 23:03 +0200, Ionut Nechita (Wind River) wrote: > From: Ionut Nechita >=20 > Hi Bjorn, >=20 > This is v10 of the fix for the SR-IOV race between driver .remove() > and concurrent hotplug events. v10 adds a second patch to fix the > AB-BA deadlock between device_lock and pci_rescan_remove_lock that > was reported by Guenter Roeck (via Google's AI review agent) and > confirmed by Benjamin Block. >=20 > The AB-BA deadlock: >=20 > CPU0 (remove_store) CPU1 (unbind_store) > -------------------- -------------------- > pci_lock_rescan_remove() > device_lock() > driver .remove() > sriov_del_vfs() > pci_lock_rescan_remove() <-- WAI= TS > pci_stop_bus_device() > device_release_driver() > device_lock() <-- WAI= TS >=20 > Patch 2/2 fixes this by calling device_release_driver() in > remove_store() before pci_stop_and_remove_bus_device_locked(), so > that the driver is already unbound when pci_rescan_remove_lock is > acquired. Both paths then take locks in the same order: device_lock > first, then pci_rescan_remove_lock. >=20 > Note: the concurrent unbind_store + hotplug-event case (where the > hotplug handler takes pci_rescan_remove_lock before device_lock) > remains a known limitation. This is a pre-existing issue that > Benjamin Block is addressing separately in: > https://lore.kernel.org/linux-pci/354b9e4a54ced67f3c89df198041df19434fe= 4c8.1773235561.git.bblock@linux.ibm.com/ >=20 --- snip --- >=20 > Ionut Nechita (2): > PCI/IOV: Make pci_lock_rescan_remove() reentrant and protect > sriov_add_vfs/sriov_del_vfs > PCI: Fix AB-BA deadlock between device_lock and > pci_rescan_remove_lock in remove_store >=20 > drivers/pci/iov.c | 9 +++++---- > drivers/pci/pci-sysfs.c | 20 +++++++++++++++++++- > drivers/pci/probe.c | 11 +++++++++-- > 3 files changed, 33 insertions(+), 7 deletions(-) >=20 > -- > 2.43.0 Hi Ionut, For your awareness, I saw that this series has some findings on Google's new Sashiko AI reviewing tool[0]. At a quick glance the findings seem like at least reasonable concerns to me. I'm still looking at this independently also of course. Thanks, Niklas [0] https://sashiko.dev/#/patchset/20260318210316.61975-1-ionut.nechita%40windr= iver.com