Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753092AbdHITqj (ORCPT ); Wed, 9 Aug 2017 15:46:39 -0400 Received: from mail.linuxfoundation.org ([140.211.169.12]:46150 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752763AbdHITnq (ORCPT ); Wed, 9 Aug 2017 15:43:46 -0400 From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Zefir Kurtisi , Florian Fainelli , "David S. Miller" , Sasha Levin Subject: [PATCH 4.4 48/58] phy state machine: failsafe leave invalid RUNNING state Date: Wed, 9 Aug 2017 12:42:00 -0700 Message-Id: <20170809194148.387183343@linuxfoundation.org> X-Mailer: git-send-email 2.14.0 In-Reply-To: <20170809194146.501519882@linuxfoundation.org> References: <20170809194146.501519882@linuxfoundation.org> User-Agent: quilt/0.65 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2048 Lines: 55 4.4-stable review patch. If anyone has any objections, please let me know. ------------------ From: Zefir Kurtisi [ Upstream commit 811a919135b980bac8009d042acdccf10dc1ef5e ] While in RUNNING state, phy_state_machine() checks for link changes by comparing phydev->link before and after calling phy_read_status(). This works as long as it is guaranteed that phydev->link is never changed outside the phy_state_machine(). If in some setups this happens, it causes the state machine to miss a link loss and remain RUNNING despite phydev->link being 0. This has been observed running a dsa setup with a process continuously polling the link states over ethtool each second (SNMPD RFC-1213 agent). Disconnecting the link on a phy followed by a ETHTOOL_GSET causes dsa_slave_get_settings() / dsa_slave_get_link_ksettings() to call phy_read_status() and with that modify the link status - and with that bricking the phy state machine. This patch adds a fail-safe check while in RUNNING, which causes to move to CHANGELINK when the link is gone and we are still RUNNING. Signed-off-by: Zefir Kurtisi Reviewed-by: Florian Fainelli Signed-off-by: David S. Miller Signed-off-by: Sasha Levin Signed-off-by: Greg Kroah-Hartman --- drivers/net/phy/phy.c | 9 +++++++++ 1 file changed, 9 insertions(+) --- a/drivers/net/phy/phy.c +++ b/drivers/net/phy/phy.c @@ -921,6 +921,15 @@ void phy_state_machine(struct work_struc if (old_link != phydev->link) phydev->state = PHY_CHANGELINK; } + /* + * Failsafe: check that nobody set phydev->link=0 between two + * poll cycles, otherwise we won't leave RUNNING state as long + * as link remains down. + */ + if (!phydev->link && phydev->state == PHY_RUNNING) { + phydev->state = PHY_CHANGELINK; + dev_err(&phydev->dev, "no link in PHY_RUNNING\n"); + } break; case PHY_CHANGELINK: err = phy_read_status(phydev);