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=-8.5 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, USER_AGENT_MUTT autolearn=ham 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 5A4C6C282DD for ; Thu, 23 May 2019 09:41:26 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 336ED2070D for ; Thu, 23 May 2019 09:41:26 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730280AbfEWJlZ (ORCPT ); Thu, 23 May 2019 05:41:25 -0400 Received: from mga18.intel.com ([134.134.136.126]:27664 "EHLO mga18.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728184AbfEWJlZ (ORCPT ); Thu, 23 May 2019 05:41:25 -0400 X-Amp-Result: UNSCANNABLE X-Amp-File-Uploaded: False Received: from orsmga007.jf.intel.com ([10.7.209.58]) by orsmga106.jf.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 23 May 2019 02:41:24 -0700 X-ExtLoop1: 1 Received: from buildpc-hp-z230.iind.intel.com (HELO buildpc-HP-Z230) ([10.223.89.34]) by orsmga007.jf.intel.com with ESMTP; 23 May 2019 02:41:21 -0700 Date: Thu, 23 May 2019 15:11:41 +0530 From: Sanyog Kale To: Srinivas Kandagatla Cc: Pierre-Louis Bossart , vkoul@kernel.org, alsa-devel@alsa-project.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] soundwire: stream: fix bad unlock balance Message-ID: <20190523094141.GA24259@buildpc-HP-Z230> References: <20190522162528.5892-1-srinivas.kandagatla@linaro.org> <4744834c-36b1-dd8d-45fa-76c75eb3d5cb@linux.intel.com> <2dc66f9d-e508-d457-a7d6-c06c4336e7b8@linaro.org> <20190523092034.GA23777@buildpc-HP-Z230> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.9.4 (2018-02-28) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, May 23, 2019 at 10:30:20AM +0100, Srinivas Kandagatla wrote: > > > On 23/05/2019 10:20, Sanyog Kale wrote: > > On Thu, May 23, 2019 at 09:43:14AM +0100, Srinivas Kandagatla wrote: > > > > > > > > > On 22/05/2019 17:41, Pierre-Louis Bossart wrote: > > > > > > > > > > > > On 5/22/19 11:25 AM, Srinivas Kandagatla wrote: > > > > > This patch fixes below warning due to unlocking without locking. > > > > > > > > > > ?? ===================================== > > > > > ?? WARNING: bad unlock balance detected! > > > > > ?? 5.1.0-16506-gc1c383a6f0a2-dirty #1523 Tainted: G?????????????? W > > > > > ?? ------------------------------------- > > > > > ?? aplay/2954 is trying to release lock (&bus->msg_lock) at: > > > > > ?? do_bank_switch+0x21c/0x480 > > > > > ?? but there are no more locks to release! > > > > > > > > > > Signed-off-by: Srinivas Kandagatla > > > > > --- > > > > > ?? drivers/soundwire/stream.c | 3 ++- > > > > > ?? 1 file changed, 2 insertions(+), 1 deletion(-) > > > > > > > > > > diff --git a/drivers/soundwire/stream.c b/drivers/soundwire/stream.c > > > > > index 544925ff0b40..d16268f30e4f 100644 > > > > > --- a/drivers/soundwire/stream.c > > > > > +++ b/drivers/soundwire/stream.c > > > > > @@ -814,7 +814,8 @@ static int do_bank_switch(struct > > > > > sdw_stream_runtime *stream) > > > > > ?????????????????????????? goto error; > > > > > ?????????????????? } > > > > > -?????????????? mutex_unlock(&bus->msg_lock); > > > > > +?????????????? if (mutex_is_locked(&bus->msg_lock)) > > > > > +?????????????????????? utex_unlock(&bus->msg_lock); > > > > > > > > Does this even compile? should be mutex_unlock, no? > > > > > > > > We also may want to identify the issue in more details without pushing > > > > it under the rug. The locking mechanism is far from simple and it's > > > > likely there are a number of problems with it. > > > > > > > msg_lock is taken conditionally during multi link bank switch cases, however > > > the unlock is done unconditionally leading to this warning. > > > > > > Having a closer look show that there could be a dead lock in this path while > > > executing sdw_transfer(). And infact there is no need to take msg_lock in > > > multi link switch cases as sdw_transfer should take care of this. > > > > > > Vinod/Sanyog any reason why msg_lock is really required in this path? > > > > > > > In case of multi link we use sdw_transfer_defer instead of sdw_transfer > > where lock is not acquired, hence lock is acquired in do_bank_switch for > > multi link. we should add same check of multi link to release lock in > > do_bank_switch. > > probably we should just add the lock around the sdw_transfer_defer call in > sdw_bank_switch()? > This should cleanup the code a bit too. > > something like: > > ------------------------------------>cut<----------------------------- > diff --git a/drivers/soundwire/stream.c b/drivers/soundwire/stream.c > index d01060dbee96..f455af5b8151 100644 > --- a/drivers/soundwire/stream.c > +++ b/drivers/soundwire/stream.c > @@ -676,10 +676,13 @@ static int sdw_bank_switch(struct sdw_bus *bus, int > m_rt_count) > */ > multi_link = bus->multi_link && (m_rt_count > 1); > > - if (multi_link) > + if (multi_link) { > + mutex_lock(&bus->msg_lock); > ret = sdw_transfer_defer(bus, wr_msg, &bus->defer_msg); > - else > + mutex_unlock(&bus->msg_lock); you cant release bus_lock here since message is not yet transferred. we can only release bus_lock after sdw_ml_sync_bank_switch function where we confirm that message transfer is completed. > + } else { > ret = sdw_transfer(bus, wr_msg); > + } > > if (ret < 0) { > dev_err(bus->dev, "Slave frame_ctrl reg write failed\n"); > @@ -742,25 +745,19 @@ static int do_bank_switch(struct sdw_stream_runtime > *stream) > struct sdw_master_runtime *m_rt = NULL; > const struct sdw_master_ops *ops; > struct sdw_bus *bus = NULL; > - bool multi_link = false; > int ret = 0; > > list_for_each_entry(m_rt, &stream->master_list, stream_node) { > bus = m_rt->bus; > ops = bus->ops; > > - if (bus->multi_link) { > - multi_link = true; > - mutex_lock(&bus->msg_lock); > - } > - > /* Pre-bank switch */ > if (ops->pre_bank_switch) { > ret = ops->pre_bank_switch(bus); > if (ret < 0) { > dev_err(bus->dev, > "Pre bank switch op failed: %d\n", > ret); > - goto msg_unlock; > + return ret; > } > } > > @@ -814,7 +811,6 @@ static int do_bank_switch(struct sdw_stream_runtime > *stream) > goto error; > } > > - mutex_unlock(&bus->msg_lock); > } > > return ret; > @@ -827,16 +823,6 @@ static int do_bank_switch(struct sdw_stream_runtime > *stream) > kfree(bus->defer_msg.msg); > } > > -msg_unlock: > - > - if (multi_link) { > - list_for_each_entry(m_rt, &stream->master_list, stream_node) > { > - bus = m_rt->bus; > - if (mutex_is_locked(&bus->msg_lock)) > - mutex_unlock(&bus->msg_lock); > - } > - } > - > return ret; > } > > ------------------------------------>cut<----------------------------- > > > > > --srini > > > > > > > > ?????????? } > > > > > ?????????? return ret; > > > > > > > --