[alsa-devel] [PATCH 0/5] ALSA: control: fix issue of concurrent access for TLV operations

[Takashi Iwai]

On Thu, 03 Aug 2017 13:20:39 +0200,
Takashi Sakamoto wrote:
> 
> Hi,
> 
> In a design of ALSA control core, each set of elements have data of
> Type-Length-Value shape. This is called as TLV data. In ALSA control
> interface, applications can three types of requests to elements about
> TLV data; read, write and command.
> 
> In current implementation of ALSA control core, these three requests
> are handled with read lock of a counting semaphore. However, this has an
> issue of concurrent access because in theory write/command requests have
> sub-effects to change state of the set of elements in a point of TLV data.
> Read requests and write/command requests are handled exclusively as well
> as each write/command requests.
> 
> This patchset is for this purpose. Additionally, this applies code
> refactoring to TLV ioctl handler and TLV handler for user-defined element
> set so that they get better shape for readers.

Taking the rw mutex outside snd_ctl_tlv_ioctl() is a good idea.
It simplified things a lot, indeed.

Now applied all patches.  Thanks!


Takashi