Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753809AbdFSSzL (ORCPT + 2 others); Mon, 19 Jun 2017 14:55:11 -0400 Received: from wtarreau.pck.nerim.net ([62.212.114.60]:52630 "EHLO 1wt.eu" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751668AbdFSSiS (ORCPT ); Mon, 19 Jun 2017 14:38:18 -0400 From: Willy Tarreau To: linux-kernel@vger.kernel.org, stable@vger.kernel.org, linux@roeck-us.net Cc: Douglas Anderson , Sumit Semwal , Willy Tarreau Subject: [PATCH 3.10 057/268] usb: hub: Wait for connection to be reestablished after port reset Date: Mon, 19 Jun 2017 20:29:16 +0200 Message-Id: <1497897167-14556-58-git-send-email-w@1wt.eu> X-Mailer: git-send-email 2.8.0.rc2.1.gbe9624a In-Reply-To: <1497897167-14556-1-git-send-email-w@1wt.eu> References: <1497897167-14556-1-git-send-email-w@1wt.eu> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Return-Path: From: Guenter Roeck commit 22547c4cc4fe20698a6a85a55b8788859134b8e4 upstream. On a system with a defective USB device connected to an USB hub, an endless sequence of port connect events was observed. The sequence of events as observed is as follows: - Port reports connected event (port status=USB_PORT_STAT_CONNECTION). - Event handler debounces port and resets it by calling hub_port_reset(). - hub_port_reset() calls hub_port_wait_reset() to wait for the reset to complete. - The reset completes, but USB_PORT_STAT_CONNECTION is not immediately set in the port status register. - hub_port_wait_reset() returns -ENOTCONN. - Port initialization sequence is aborted. - A few milliseconds later, the port again reports a connected event, and the sequence repeats. This continues either forever or, randomly, stops if the connection is already re-established when the port status is read. It results in a high rate of udev events. This in turn destabilizes userspace since the above sequence holds the device mutex pretty much continuously and prevents userspace from actually reading the device status. To prevent the problem from happening, let's wait for the connection to be re-established after a port reset. If the device was actually disconnected, the code will still return an error, but it will do so only after the long reset timeout. Cc: Douglas Anderson Signed-off-by: Guenter Roeck Acked-by: Alan Stern Signed-off-by: Sumit Semwal Signed-off-by: Willy Tarreau --- drivers/usb/core/hub.c | 11 +++++++++-- 1 file changed, 9 insertions(+), 2 deletions(-) diff --git a/drivers/usb/core/hub.c b/drivers/usb/core/hub.c index 4e5156d..55a8e84 100644 --- a/drivers/usb/core/hub.c +++ b/drivers/usb/core/hub.c @@ -2579,8 +2579,15 @@ static int hub_port_wait_reset(struct usb_hub *hub, int port1, if (ret < 0) return ret; - /* The port state is unknown until the reset completes. */ - if (!(portstatus & USB_PORT_STAT_RESET)) + /* + * The port state is unknown until the reset completes. + * + * On top of that, some chips may require additional time + * to re-establish a connection after the reset is complete, + * so also wait for the connection to be re-established. + */ + if (!(portstatus & USB_PORT_STAT_RESET) && + (portstatus & USB_PORT_STAT_CONNECTION)) break; /* switch to the long delay after two short delay failures */ -- 2.8.0.rc2.1.gbe9624a