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AL+hErH/0gE3DCIZT3x59Z30pfhlY9yO/q9q3Jaz8Q9Lnsw0TqRoyNeT4R6fo+/zWKN/rLSqm8wrVDtcC03vDCU=@vger.kernel.org X-Gm-Message-State: APuU4Z/k3vz8o1n55wHZz8u1iDuFvOFe39qTJOmdfFXoFy2tX/D6BlOY 5ZATpNvZUjVUeommVGzxl7PB7EgSpqa25hTaUV3s17If420GRn5LzGlTKPhbZlkvE3y0ofjq4pc LbsIlbWBBWfYbCw== X-Received: from pla14.prod.google.com ([2002:a17:902:ffce:b0:2ea:7f9c:2ce]) (user=rickyniu job=prod-delivery.src-stubby-dispatcher) by 2002:a17:902:ccc4:b0:2ed:118e:7faa with SMTP id d9443c01a7336-2ee0de19c7cmr12354605ad.37.1794543605590; Thu, 12 Nov 2026 20:20:05 -0800 (PST) Date: Fri, 13 Nov 2026 04:02:37 +0000 X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list Mime-Version: 1.0 Message-ID: <20261113041948.1280304-1-rickyniu@google.com> Subject: [PATCH 0/2] usb: Fix giveback_urb_bh deadlock on URB dequeue From: Chien Kun Niu To: Greg Kroah-Hartman , Mathias Nyman Cc: Alan Stern , linux-usb@vger.kernel.org, linux-kernel@vger.kernel.org, Chien Kun Niu Content-Type: text/plain; charset="UTF-8" We hit a CPU hardlockup during reboot while usbnet was unlinking queued RX URBs on a halted xHCI controller. In xhci_urb_dequeue(), the err_giveback path releases xhci->lock and restores interrupts before calling usb_hcd_giveback_urb(). Because usb_hcd_giveback_urb() takes bh->lock with plain spin_lock(), an interrupt arriving on the same CPU can deadlock on bh->lock either in usb_hcd_irq() or when softirq runs usb_giveback_urb_bh(). Patch 1 switches usb_hcd_giveback_urb() to spin_lock_irqsave() since bh->lock is also acquired in hardirq and BH contexts. Patch 2 keeps xhci->lock held across usb_hcd_giveback_urb() in xhci_urb_dequeue(), matching xhci_giveback_urb_in_irq() and keeping per-endpoint URB giveback ordering serialized. The two patches are independent and can be applied in either order. Chien Kun Niu (2): usb: core: hcd: Disable IRQs when taking bh->lock xhci: Give back URB under lock in xhci_urb_dequeue() drivers/usb/core/hcd.c | 5 +++-- drivers/usb/host/xhci.c | 2 +- 2 files changed, 4 insertions(+), 3 deletions(-) base-commit: b3dfbde62cf1981c4638939c159dfd087b7a72e9 -- 2.56.0.567.gdb80ae8cd5-goog