From mboxrd@z Thu Jan 1 00:00:00 1970 From: Pierre-Louis Bossart Subject: Re: [PATCH v5 6/9] soundwire: Handle multiple master instances in a stream Date: Tue, 10 Jul 2018 13:16:30 -0500 Message-ID: <39c187f6-f9d6-4f01-81db-8ddba35572d7@linux.intel.com> References: <1530791196-15483-1-git-send-email-shreyas.nc@intel.com> <1530791196-15483-7-git-send-email-shreyas.nc@intel.com> <19b89cc8-b97e-dd43-3d96-8c5bdcb5287d@linux.intel.com> <20180710170229.GB22349@buildpc-HP-Z230> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii"; Format="flowed" Content-Transfer-Encoding: 7bit Return-path: Received: from mga14.intel.com (mga14.intel.com [192.55.52.115]) by alsa0.perex.cz (Postfix) with ESMTP id 44B6F267700 for ; Tue, 10 Jul 2018 20:16:34 +0200 (CEST) In-Reply-To: <20180710170229.GB22349@buildpc-HP-Z230> Content-Language: en-US List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: alsa-devel-bounces@alsa-project.org Sender: alsa-devel-bounces@alsa-project.org To: Sanyog Kale Cc: patches.audio@intel.com, gregkh@linuxfoundation.org, alsa-devel@alsa-project.org, vkoul@kernel.org, Shreyas NC List-Id: alsa-devel@alsa-project.org On 7/10/18 12:02 PM, Sanyog Kale wrote: > On Mon, Jul 09, 2018 at 06:42:34PM -0500, Pierre-Louis Bossart wrote: >> Sorry, another issue that I found while reviewing the entire section. >>> } >>> @@ -888,6 +918,7 @@ static void sdw_release_slave_stream(struct sdw_slave *slave, >>> /** >>> * sdw_release_master_stream() - Free Master runtime handle >>> * >>> + * @m_rt: Master runtime node >>> * @stream: Stream runtime handle. >>> * >>> * This function is to be called with bus_lock held >>> @@ -895,16 +926,18 @@ static void sdw_release_slave_stream(struct sdw_slave *slave, >>> * handle. If this is called first then sdw_release_slave_stream() will have >>> * no effect as Slave(s) runtime handle would already be freed up. >>> */ >>> -static void sdw_release_master_stream(struct sdw_stream_runtime *stream) >>> +static void sdw_release_master_stream(struct sdw_master_runtime *m_rt, >>> + struct sdw_stream_runtime *stream) >>> { >>> - struct sdw_master_runtime *m_rt = stream->m_rt; >>> struct sdw_slave_runtime *s_rt, *_s_rt; >>> list_for_each_entry_safe(s_rt, _s_rt, >>> &m_rt->slave_rt_list, m_rt_node) >>> sdw_stream_remove_slave(s_rt->slave, stream); >>> + list_del(&m_rt->stream_node); >>> list_del(&m_rt->bus_node); >>> + kfree(m_rt); >>> } >>> /** >>> @@ -918,13 +951,22 @@ static void sdw_release_master_stream(struct sdw_stream_runtime *stream) >>> int sdw_stream_remove_master(struct sdw_bus *bus, >>> struct sdw_stream_runtime *stream) >>> { >>> + struct sdw_master_runtime *m_rt, *_m_rt; >>> + >>> mutex_lock(&bus->bus_lock); >>> - sdw_release_master_stream(stream); >>> - sdw_master_port_release(bus, stream->m_rt); >>> - stream->state = SDW_STREAM_RELEASED; >>> - kfree(stream->m_rt); >>> - stream->m_rt = NULL; >>> + list_for_each_entry_safe(m_rt, _m_rt, >>> + &stream->master_list, stream_node) { >>> + >>> + if (m_rt->bus != bus) >>> + continue; >>> + >>> + sdw_master_port_release(bus, m_rt); >>> + sdw_release_master_stream(m_rt, stream); >>> + } >>> + >>> + if (list_empty(&stream->master_list)) >>> + stream->state = SDW_STREAM_RELEASED; >>> mutex_unlock(&bus->bus_lock); >>> >> So the sequence is >> >> mutex_lock >> sdw_master_port_release() >> sdw_release_master_stream() >> ?????? sdw_stream_remove_slave() >> ?????? ?????? mutex_lock >> >> Is this intentional to take the same mutex twice (not sure if it even >> works). > > sdw_stream_remove_slave is called from sdw_release_master_stream to make > sure all Slave(s) resources are freed up before freeing Master. > sdw_stream_remove_slave is also called by Slave driver to free up Slave > resources. In either case, we wanted to make sure the bus_lock is held > hence the bus lock is held in sdw_stream_remove_slave API as well. Yes, it's fine to take the lock from sdw_stream_remove_slave(), the point was to avoid taking the lock twice when the master is removed first. > > It doesnt look correct to take same mutex twice. Will check on this. > >> what you probably wanted is to replace sdw_stream_remove_slave() by the >> equivalent sequence >> >> sdw_slave_port_release() >> sdw_release_slave_stream() >> >> which are both supposed to be called with a bus_lock held. > > you mean to say perform sdw_slave_port_release and > sdw_release_slave_stream in sdw_release_master_stream instead of calling > sdw_stream_remove_slave?? Yes, something like the change below: static void sdw_release_master_stream(struct sdw_master_runtime *m_rt, struct sdw_stream_runtime *stream) { struct sdw_master_runtime *m_rt = stream->m_rt; struct sdw_slave_runtime *s_rt, *_s_rt; list_for_each_entry_safe(s_rt, _s_rt, &m_rt->slave_rt_list, m_rt_node) - sdw_stream_remove_slave(s_rt->slave, stream); + sdw_slave_port_release() + sdw_release_slave_stream() list_del(&m_rt->stream_node); list_del(&m_rt->bus_node); kfree(m_rt); }