On Mon, 3 Dec 2001, Alexander Ehlert wrote:
> Hi,
>
> can it be, that snd_pcm_open in the alsa lib is not threadsafe?
You're right, the snd_config_update() function is not thread safe (it uses
global variables). I put this item to the todo list.
> Glame uses threads for all its plugins and if I have for example
> one audio_in and one audio_out plugin, it can happen, that
> snd_pcm_open is called twice at the same time. Wonderful things
> happen in snd_config_expand and glame can't open any audio devices
> with alsa for a running session. Putting mutexes around snd_pcm_open
> fixes the problem. Are there any other functions in the alsa lib
> that are potentially not thread safe?
Other functions should be thread safe (except pcm_share plugin), because
they are using different handlers and data structures. Only functions
operating with the ring buffer (snd_pcm_write*/snd_pcm_read*) and
setting parameters (snd_pcm_hw_params, snd_pcm_sw_params) should
be called only from one thread, otherwise a data inconsistency
situation can be occured. I'm speaking about same snd_pcm_t handle, if
handles are different, there is no problem to call all mentioned functions
simultaneously.
Jaroslav
-----
Jaroslav Kysela <[EMAIL PROTECTED]>
SuSE Linux http://www.suse.com
ALSA Project http://www.alsa-project.org
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