From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-9.7 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED,USER_AGENT_GIT autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 85FB8C432C3 for ; Thu, 14 Nov 2019 18:21:26 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 5996B2072C for ; Thu, 14 Nov 2019 18:21:26 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727434AbfKNSVY (ORCPT ); Thu, 14 Nov 2019 13:21:24 -0500 Received: from mga03.intel.com ([134.134.136.65]:36344 "EHLO mga03.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727054AbfKNSRd (ORCPT ); Thu, 14 Nov 2019 13:17:33 -0500 X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from orsmga007.jf.intel.com ([10.7.209.58]) by orsmga103.jf.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 14 Nov 2019 10:17:32 -0800 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.68,304,1569308400"; d="scan'208";a="195123378" Received: from chiahuil-mobl.amr.corp.intel.com (HELO pbossart-mobl3.amr.corp.intel.com) ([10.255.228.77]) by orsmga007.jf.intel.com with ESMTP; 14 Nov 2019 10:17:30 -0800 From: Pierre-Louis Bossart To: alsa-devel@alsa-project.org Cc: linux-kernel@vger.kernel.org, tiwai@suse.de, broonie@kernel.org, vkoul@kernel.org, gregkh@linuxfoundation.org, jank@cadence.com, srinivas.kandagatla@linaro.org, slawomir.blauciak@intel.com, Bard liao , Rander Wang , Ranjani Sridharan , Pierre-Louis Bossart , Rander Wang , Sanyog Kale Subject: [PATCH v3 02/22] soundwire: bus: fix race condition with probe_complete signaling Date: Thu, 14 Nov 2019 12:16:42 -0600 Message-Id: <20191114181702.22254-3-pierre-louis.bossart@linux.intel.com> X-Mailer: git-send-email 2.20.1 In-Reply-To: <20191114181702.22254-1-pierre-louis.bossart@linux.intel.com> References: <20191114181702.22254-1-pierre-louis.bossart@linux.intel.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org The driver probe takes care of basic initialization and is invoked when a Slave becomes attached, after a match between the Slave DevID registers and ACPI/DT entries. The update_status callback is invoked when a Slave state changes, e.g. when it is assigned a non-zero Device Number and it reports with an ATTACHED/ALERT state. The state change detection is usually hardware-based and based on the SoundWire frame rate (e.g. double-digit microseconds) while the probe is a pure software operation, which may involve a kernel module load. In corner cases, it's possible that the state changes before the probe completes. This patch suggests the use of wait_for_completion to avoid races on startup, so that the update_status callback does not rely on invalid pointers/data structures. Signed-off-by: Rander Wang Signed-off-by: Pierre-Louis Bossart --- drivers/soundwire/bus.c | 25 ++++++++++++++++++++++--- drivers/soundwire/bus.h | 1 + drivers/soundwire/bus_type.c | 5 +++++ drivers/soundwire/slave.c | 2 ++ 4 files changed, 30 insertions(+), 3 deletions(-) diff --git a/drivers/soundwire/bus.c b/drivers/soundwire/bus.c index 4b22ee996a65..d99acbc614c6 100644 --- a/drivers/soundwire/bus.c +++ b/drivers/soundwire/bus.c @@ -961,10 +961,29 @@ static int sdw_handle_slave_alerts(struct sdw_slave *slave) static int sdw_update_slave_status(struct sdw_slave *slave, enum sdw_slave_status status) { - if (slave->ops && slave->ops->update_status) - return slave->ops->update_status(slave, status); + unsigned long time; - return 0; + if (!slave->probed) { + /* + * the slave status update is typically handled in an + * interrupt thread, which can race with the driver + * probe, e.g. when a module needs to be loaded. + * + * make sure the probe is complete before updating + * status. + */ + time = wait_for_completion_timeout(&slave->probe_complete, + msecs_to_jiffies(DEFAULT_PROBE_TIMEOUT)); + if (!time) { + dev_err(&slave->dev, "Probe not complete, timed out\n"); + return -ETIMEDOUT; + } + } + + if (!slave->ops || !slave->ops->update_status) + return 0; + + return slave->ops->update_status(slave, status); } /** diff --git a/drivers/soundwire/bus.h b/drivers/soundwire/bus.h index be01a5f3d00b..93e7bbab0938 100644 --- a/drivers/soundwire/bus.h +++ b/drivers/soundwire/bus.h @@ -5,6 +5,7 @@ #define __SDW_BUS_H #define DEFAULT_BANK_SWITCH_TIMEOUT 3000 +#define DEFAULT_PROBE_TIMEOUT 2000 int sdw_uevent(struct device *dev, struct kobj_uevent_env *env); diff --git a/drivers/soundwire/bus_type.c b/drivers/soundwire/bus_type.c index df1271f6db61..c9dbc98ac028 100644 --- a/drivers/soundwire/bus_type.c +++ b/drivers/soundwire/bus_type.c @@ -120,6 +120,11 @@ static int sdw_slave_drv_probe(struct device *dev) slave->bus->clk_stop_timeout = max_t(u32, slave->bus->clk_stop_timeout, slave->prop.clk_stop_timeout); + slave->probed = true; + complete(&slave->probe_complete); + + dev_dbg(dev, "probe complete\n"); + return 0; } diff --git a/drivers/soundwire/slave.c b/drivers/soundwire/slave.c index 014c3ece1f17..15ac89ecae01 100644 --- a/drivers/soundwire/slave.c +++ b/drivers/soundwire/slave.c @@ -53,6 +53,8 @@ static int sdw_slave_add(struct sdw_bus *bus, slave->bus = bus; slave->status = SDW_SLAVE_UNATTACHED; slave->dev_num = 0; + init_completion(&slave->probe_complete); + slave->probed = false; mutex_lock(&bus->bus_lock); list_add_tail(&slave->node, &bus->slaves); -- 2.20.1