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

[Takashi Sakamoto]

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.

Takashi Sakamoto (5):
  ALSA: control: queue events within locking of controls_rwsem for TLV
    operation
  ALSA: control: use counting semaphore as write lock for TLV
    write/command operations
  ALSA: control: obsolete user_ctl_lock
  ALSA: control: code refactoring TLV ioctl handler
  ALSA: control: code refactoring for TLV request handler to user
    element set

 include/sound/core.h |   2 -
 sound/core/control.c | 252 +++++++++++++++++++++++++++++++--------------------
 sound/core/init.c    |   1 -
 3 files changed, 155 insertions(+), 100 deletions(-)

-- 
2.11.0