mirrors/alsa-lib
1
0
Fork 0
mirror of https://github.com/alsa-project/alsa-lib.git synced 2025-10-29 05:40:25 -04:00
Code Issues Projects Releases Packages Wiki Activity Actions

conf: Add thread-safe global tree reference

Browse source 
Most of open functions in alsa-lib have the call pattern:
  snd_config_update();
  return snd_xxx_open(x, snd_config, ...);

This means that the toplevel config gets updated, and passed to a
local open function.  Although snd_config_update() itself has a
pthread mutex to be thread safe, the whole procedure above isn't
thread safe.  Namely, the global snd_config tree may be deleted and
recreated at any time while the open function is being processed.
This may lead to a data corruption and crash of the program.

For avoiding the corruption, this patch introduces a refcount to
config tree object.  A few new helper functions are introduced as
well:
- snd_config_update_ref() does update and take the refcount of the
  toplevel tree.   The obtained config tree has to be freed via
  snd_config_unref() below.
- snd_config_ref() and snd_config_unref() manage the refcount of the
  config object.  The latter eventually deletes the object when all
  references are gone.

Along with these additions, the caller of snd_config_update() and
snd_config global tree in alsa-lib are replaced with the new helpers.

Signed-off-by: Takashi Iwai <tiwai@suse.de>
This commit is contained in:
Takashi Iwai 2016-05-17 15:39:07 +02:00
parent 5fb3fe1724
commit c9a0d7d601
9 changed files with 125 additions and 14 deletions
Download patch file Download diff file Expand all files Collapse all files

8
src/pcm/pcm.c
View file

@ -2288,12 +2288,16 @@ static int snd_pcm_open_noupdate(snd_pcm_t **pcmp, snd_config_t *root,
int snd_pcm_open(snd_pcm_t **pcmp, const char *name,
snd_pcm_stream_t stream, int mode)
{
snd_config_t *top;
int err;
assert(pcmp && name);
err = snd_config_update();
err = snd_config_update_ref(&top);
if (err < 0)
return err;
return snd_pcm_open_noupdate(pcmp, snd_config, name, stream, mode, 0);
err = snd_pcm_open_noupdate(pcmp, top, name, stream, mode, 0);
snd_config_unref(top);
return err;
}
/**