a4857d1afd
Always add buses to the stream->master_list in a fixed order. The unique bus->id is used to order the adding of buses to the list. This prevents lockdep asserts and possible deadlocks on streams that have multiple buses. sdw_acquire_bus_lock() takes bus_lock in the order that buses are listed in stream->master_list. do_bank_switch() takes all the msg_lock in the same order. To prevent a lockdep assert, and a possible real deadlock, the relative order of taking these mutexes must always be the same. For example, if a stream takes the mutexes in the order (bus0, bus1) lockdep will assert if another stream takes them in the order (bus1, bus0). More complex relative ordering will also assert, for example if two streams take (bus0, bus1) and (bus1, bus2), then a third stream takes (bus2, bus0). Previously sdw_stream_add_master() simply added the given bus to the end of the list, requiring the caller to guarantee that buses are added in a fixed order. This isn't reasonable or necessary - it's an internal implementation detail that should not be exposed by the API. It doesn't really make sense when there could be multiple independent calling drivers, to say "you must add your buses in the same order as a different driver, that you don't know about, added them". Signed-off-by: Richard Fitzgerald <rf@opensource.cirrus.com> Reviewed-by: Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com> Link: https://lore.kernel.org/r/20230615141208.679011-2-rf@opensource.cirrus.com Signed-off-by: Vinod Koul <vkoul@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.