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Mon, 20 Apr 2026 15:45:00 +0000 (GMT) Received: from p1gen4-pw042f0m (unknown [9.52.223.163]) by smtpav06.fra02v.mail.ibm.com (Postfix) with ESMTPS; Mon, 20 Apr 2026 15:45:00 +0000 (GMT) Received: from bblock by p1gen4-pw042f0m with local (Exim 4.99.1) (envelope-from ) id 1wEqnz-00000002hi8-3kSI; Mon, 20 Apr 2026 17:44:59 +0200 Date: Mon, 20 Apr 2026 17:44:59 +0200 From: Benjamin Block To: "Ionut Nechita (Wind River)" Cc: linux-pci@vger.kernel.org, bhelgaas@google.com, helgaas@kernel.org, sebott@linux.ibm.com, schnelle@linux.ibm.com, linux@roeck-us.net, lukas@wunner.de, stable@vger.kernel.org, linux-kernel@vger.kernel.org, intel-xe@lists.freedesktop.org, matthew.brost@intel.com, michal.wajdeczko@intel.com, piotr.piorkowski@intel.com, dtatulea@nvidia.com, mani@kernel.org, kbusch@kernel.org, lkml@mageta.org, alifm@linux.ibm.com, julianr@linux.ibm.com, ionut_n2001@yahoo.com, sunlightlinux@gmail.com Subject: Re: [PATCH v11 2/2] PCI: Fix AB-BA deadlock between device_lock and pci_rescan_remove_lock in remove_store Message-ID: <20260420154459.GA2707369@p1gen4-pw042f0m> References: <20260326083534.23602-1-ionut.nechita@windriver.com> <20260326083534.23602-3-ionut.nechita@windriver.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20260326083534.23602-3-ionut.nechita@windriver.com> Sender: Benjamin Block X-TM-AS-GCONF: 00 X-Proofpoint-Reinject: loops=2 maxloops=12 X-Authority-Analysis: v=2.4 cv=L78theT8 c=1 sm=1 tr=0 ts=69e64a02 cx=c_pps a=3Bg1Hr4SwmMryq2xdFQyZA==:117 a=3Bg1Hr4SwmMryq2xdFQyZA==:17 a=8nJEP1OIZ-IA:10 a=A5OVakUREuEA:10 a=VkNPw1HP01LnGYTKEx00:22 a=RnoormkPH1_aCDwRdu11:22 a=RzCfie-kr_QcCd8fBx8p:22 a=VwQbUJbxAAAA:8 a=_jlGtV7tAAAA:8 a=p2eoyRXnAAAA:8 a=VnNF1IyMAAAA:8 a=t7CeM3EgAAAA:8 a=38I2V2JNsOjyXGpjdSMA:9 a=3ZKOabzyN94A:10 a=wPNLvfGTeEIA:10 a=nlm17XC03S6CtCLSeiRr:22 a=KSHYvF9M28j0gckGFaEs:22 a=FdTzh2GWekK77mhwV6Dw:22 X-Proofpoint-Spam-Details-Enc: AW1haW4tMjYwNDIwMDE1MCBTYWx0ZWRfX9+HYG0zg13HD X8IaCoDz5SaK7kzmmd+5ikBq0D0pYM+LSYieRugIpTLumhJ0pyId6YwTpFp304BqzlCq0gVbwwt E/sUkUVa+jZv30/gmBW7FaWeirvVJlV9G9AY7UrB6Z4tvc1zD9tsDI6ToY8znrCJMDofdTjcgLL vWeRdQ5xhJh1hoknt4DpJUk2X0I6c7kz2SBwZRUZ69RIQA79oAKgpRrUVpRojHfLfQxXJlVxFal Io7tjFMEHlnUz9lpoM/D10GwBek07/dZjGjbKyvMiZ2nCihdKObkxDsX4ttKOUFn1zrE1vLUEfC JRZ4bZh7M/n/or7fFzhjtJbiV4GagKR8X4o7cUU8np7UDulSeDTIdAEq/clBME0ahOYkB+Usi+p EH71j0jm/sbHYA18vSDmwv+HgsuFiXEjXGdiGXIUvbyjXVrzRbCIXoPbzSGMQ8EbvpxJ9EtFIGa E5C5Db7zrbm0TITiHCw== X-Proofpoint-GUID: 2aQkmJIgEF6oHEufyLTzgYL4HSGwrj6v X-Proofpoint-ORIG-GUID: mdSpiUkZJHREJzle4vcqThZCVQUI064d X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1143,Hydra:6.1.51,FMLib:17.12.100.49 definitions=2026-04-20_03,2026-04-20_02,2025-10-01_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 priorityscore=1501 impostorscore=0 spamscore=0 bulkscore=0 suspectscore=0 lowpriorityscore=0 adultscore=0 clxscore=1015 malwarescore=0 phishscore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.22.0-2604070000 definitions=main-2604200150 Hey Ionut, On Thu, Mar 26, 2026 at 10:35:34AM +0200, Ionut Nechita (Wind River) wrote: > remove_store() calls pci_stop_and_remove_bus_device_locked() which > takes pci_rescan_remove_lock first, then device_lock during driver > release. Meanwhile, unbind_store() takes device_lock first (via > device_driver_detach), and the driver's .remove() callback may call > pci_disable_sriov() -> sriov_del_vfs() -> pci_lock_rescan_remove(). > > This creates an AB-BA deadlock: > > CPU0 (remove_store) CPU1 (unbind_store) > -------------------- -------------------- > pci_lock_rescan_remove() > device_lock() > driver .remove() > sriov_del_vfs() > pci_lock_rescan_remove() <-- WAITS > pci_stop_bus_device() > device_release_driver() > device_lock() <-- WAITS > > Fix this by first marking the device as dead using kill_device() to > prevent any new driver from binding, then calling device_release_driver() > before pci_stop_and_remove_bus_device_locked(). > > Marking the device dead closes the race window between unbinding and > removal where a new driver could theoretically bind: once the dead flag > is set, the device core will refuse any new driver probe. > > After device_release_driver() returns, the driver is already unbound, > so the subsequent device_release_driver() call inside > pci_stop_and_remove_bus_device_locked() becomes a no-op. > > Fixes: a5338e365c45 ("PCI/IOV: Fix race between SR-IOV enable/disable and hotplug") > Reported-by: Guenter Roeck > Closes: https://lore.kernel.org/linux-pci/0ca9e675-478c-411d-be32-e2d81439288f@roeck-us.net/ > Reported-by: Benjamin Block > Closes: https://lore.kernel.org/linux-pci/20260317090149.GA3835708@chlorum.ategam.org/ > Suggested-by: Benjamin Block > Cc: stable@vger.kernel.org > Signed-off-by: Ionut Nechita > --- > drivers/pci/pci-sysfs.c | 30 +++++++++++++++++++++++++++++- > 1 file changed, 29 insertions(+), 1 deletion(-) sorry for the late response, it slipped past me that I haven't given this a review yet. It looks fine to me. It solves the report we had with the previous patch. I also tested this, and so far it looks good in my (s390) setup. Reviewed-by: Benjamin Block Tested-by: Benjamin Block -- Best Regards, Benjamin Block / Linux on IBM Z Kernel Development IBM Deutschland Research & Development GmbH / https://www.ibm.com/privacy Vors. Aufs.-R.: Wolfgang Wendt / Geschäftsführung: David Faller Sitz der Ges.: Ehningen / Registergericht: AmtsG Stuttgart, HRB 243294