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[220.135.95.34]) by smtp.gmail.com with ESMTPSA id d9443c01a7336-20e7f0dba22sm42542085ad.220.2024.10.22.06.02.45 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 22 Oct 2024 06:02:45 -0700 (PDT) Sender: AceLan Kao From: "Chia-Lin Kao (AceLan)" To: Bjorn Helgaas , =?UTF-8?q?Ilpo=20J=C3=A4rvinen?= , Lukas Wunner , linux-pci@vger.kernel.org, linux-kernel@vger.kernel.org Subject: [PATCH v2] PCI: pciehp: Fix system hang during resume with daisy-chained hotplug controllers Date: Tue, 22 Oct 2024 21:02:43 +0800 Message-ID: <20241022130243.263737-1-acelan.kao@canonical.com> X-Mailer: git-send-email 2.43.0 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" A system hang occurs when multiple PCIe hotplug controllers in a daisy-chai= ned setup (like a Thunderbolt dock with NVMe storage) resume from system sleep. This happens when both the dock and its downstream devices try to process P= DC events at the same time through pciehp_request(). This patch changes pciehp_request() to atomic_or(), which adds the PDC even= t to ctrl->pending_events atomically. This change prevents the race condition by making the event handling atomic across multiple hotplug controllers during resume. The bug was found with an Intel Thunderbolt 4 Bridge (8086:0b26) dock and a Phison NVMe controller (1987:5012), where the system would hang if both dev= ices tried to handle presence detect changes during resume. Changes: v2: * Replace pciehp_request() with atomic_or() to fix race condition v1: * https://lore.kernel.org/lkml/Zvf7xYEA32VgLRJ6@wunner.de/T/ * Remove pci_walk_bus() call * Fix appeared to work due to lower reproduction rate Fixes: 9d573d19547b ("PCI: pciehp: Detect device replacement during system = sleep") Signed-off-by: Chia-Lin Kao (AceLan) --- drivers/pci/hotplug/pciehp_core.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/drivers/pci/hotplug/pciehp_core.c b/drivers/pci/hotplug/pciehp= _core.c index ff458e692fed..56bf23d55c41 100644 --- a/drivers/pci/hotplug/pciehp_core.c +++ b/drivers/pci/hotplug/pciehp_core.c @@ -332,7 +332,7 @@ static int pciehp_resume_noirq(struct pcie_device *dev) ctrl_dbg(ctrl, "device replaced during system sleep\n"); pci_walk_bus(ctrl->pcie->port->subordinate, pci_dev_set_disconnected, NULL); - pciehp_request(ctrl, PCI_EXP_SLTSTA_PDC); + atomic_or(PCI_EXP_SLTSTA_PDC, &ctrl->pending_events); } } =20 --=20 2.43.0