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The use_count of the swidget is protect by ALSA core PCM locking with the exception when an associated kcontrol is changed. It has been observed that a rightly timed kcontrol access during stream stop can result of an attempt to send a control update to a widget which has been freed up between the check of the use_count and the message sending. We need to protect the entire sof_widget_setup() and sof_widget_free() execution to make it safe to rely on the use_count. Move the code under an _unlocked() function and use a mutex to protect the execution of the functions for concurrency. On the control path we need to use the lock only for the kcontrol access, the widget_kcontrol_setup() op is called with the lock already held. Reported-by: Guennadi Liakhovetski <guennadi.liakhovetski@linux.intel.com> Signed-off-by: Peter Ujfalusi <peter.ujfalusi@linux.intel.com> Reviewed-by: Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com> Reviewed-by: Ranjani Sridharan <ranjani.sridharan@linux.intel.com> Link: https://lore.kernel.org/r/20230127120031.10709-18-peter.ujfalusi@linux.intel.com Signed-off-by: Mark Brown <broonie@kernel.org>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.