Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S936757AbdCJMl7 (ORCPT ); Fri, 10 Mar 2017 07:41:59 -0500 Received: from shadbolt.e.decadent.org.uk ([88.96.1.126]:45098 "EHLO shadbolt.e.decadent.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S936668AbdCJMNh (ORCPT ); Fri, 10 Mar 2017 07:13:37 -0500 Content-Type: text/plain; charset="UTF-8" Content-Disposition: inline Content-Transfer-Encoding: 8bit MIME-Version: 1.0 From: Ben Hutchings To: linux-kernel@vger.kernel.org, stable@vger.kernel.org CC: akpm@linux-foundation.org, "Greg Kroah-Hartman" , "Mathias Nyman" Date: Fri, 10 Mar 2017 11:46:23 +0000 Message-ID: X-Mailer: LinuxStableQueue (scripts by bwh) Subject: [PATCH 3.16 216/370] xhci: fix deadlock at host remove by running watchdog correctly In-Reply-To: X-SA-Exim-Connect-IP: 82.70.136.246 X-SA-Exim-Mail-From: ben@decadent.org.uk X-SA-Exim-Scanned: No (on shadbolt.decadent.org.uk); SAEximRunCond expanded to false Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3097 Lines: 77 3.16.42-rc1 review patch. If anyone has any objections, please let me know. ------------------ From: Mathias Nyman commit d6169d04097fd9ddf811e63eae4e5cd71e6666e2 upstream. If a URB is killed while the host is removed we can end up in a situation where the hub thread takes the roothub device lock, and waits for the URB to be given back by xhci-hcd, blocking the host remove code. xhci-hcd tries to stop the endpoint and give back the urb, but can't as the host is removed from PCI bus at the same time, preventing the normal way of giving back urb. Instead we need to rely on the stop command timeout function to give back the urb. This xhci_stop_endpoint_command_watchdog() timeout function used a XHCI_STATE_DYING flag to indicate if the timeout function is already running, but later this flag has been taking into use in other places to mark that xhci is dying. Remove checks for XHCI_STATE_DYING in xhci_urb_dequeue. We are still checking that reading from pci state does not return 0xffffffff or that host is not halted before trying to stop the endpoint. This whole area of stopping endpoints, giving back URBs, and the wathdog timeout need rework, this fix focuses on solving a specific deadlock issue that we can then send to stable before any major rework. Signed-off-by: Mathias Nyman Signed-off-by: Greg Kroah-Hartman [bwh: Backported to 3.16: the checks look slightly different] Signed-off-by: Ben Hutchings --- drivers/usb/host/xhci-ring.c | 11 ----------- drivers/usb/host/xhci.c | 13 ------------- 2 files changed, 24 deletions(-) --- a/drivers/usb/host/xhci-ring.c +++ b/drivers/usb/host/xhci-ring.c @@ -878,13 +878,6 @@ void xhci_stop_endpoint_command_watchdog spin_lock_irqsave(&xhci->lock, flags); ep->stop_cmds_pending--; - if (xhci->xhc_state & XHCI_STATE_DYING) { - xhci_dbg_trace(xhci, trace_xhci_dbg_cancel_urb, - "Stop EP timer ran, but another timer marked " - "xHCI as DYING, exiting."); - spin_unlock_irqrestore(&xhci->lock, flags); - return; - } if (!(ep->stop_cmds_pending == 0 && (ep->ep_state & EP_HALT_PENDING))) { xhci_dbg_trace(xhci, trace_xhci_dbg_cancel_urb, "Stop EP timer ran, but no command pending, " --- a/drivers/usb/host/xhci.c +++ b/drivers/usb/host/xhci.c @@ -1561,19 +1561,6 @@ int xhci_urb_dequeue(struct usb_hcd *hcd xhci_urb_free_priv(xhci, urb_priv); return ret; } - if ((xhci->xhc_state & XHCI_STATE_DYING) || - (xhci->xhc_state & XHCI_STATE_HALTED)) { - xhci_dbg_trace(xhci, trace_xhci_dbg_cancel_urb, - "Ep 0x%x: URB %p to be canceled on " - "non-responsive xHCI host.", - urb->ep->desc.bEndpointAddress, urb); - /* Let the stop endpoint command watchdog timer (which set this - * state) finish cleaning up the endpoint TD lists. We must - * have caught it in the middle of dropping a lock and giving - * back an URB. - */ - goto done; - } ep_index = xhci_get_endpoint_index(&urb->ep->desc); ep = &xhci->devs[urb->dev->slot_id]->eps[ep_index];