'Twas brillig, and Lennart Poettering at 01/03/09 09:40 did gyre and gimble:
On Sun, 01.03.09 02:27, Colin Guthrie (gm...@colin.guthr.ie) wrote:
Hi,
I was trying to debug a deadlock while using gvim (with
libcanberra+pulse output: https://qa.mandriva.com/show_bug.cgi?id=44925)
I had reason to read the threaded loop docs.
The reference implementation shown here:
http://0pointer.de/lennart/projects/pulseaudio/doxygen/threaded_mainloop.html#basic_subsec
In my mind, the operation could theoretically be cancelled and this the
_get_state() will return PA_OPERATION_CANCELLED.
In the example code, if this happens, the loop will spin and the main
loop will never be unlocked.
This could be fixed by spinning when the state is PA_OPERATION_RUNNING
rather when it is not PA_OPERATION_DONE (incidentally, there is a typo
in the docs... it says OPERATION_RUNNING without the PA_ prefix...).
Anyway, any comments on this observation would be appreciated.
PA_OPERATION_CANCELLED is a state that is only entered after the
*client* called pa_operation_cancel(), i.e. it needs to be triggered
from the same code that waits for pa_operation_get_state() becoming
PA_OPERATION_DONE. Hence waiting for _DONE is actually safe.
That said it is probably still more robust if we'd only loop as long
as _RUNNING is the current state so that this loop properly exits
should the client code be eventullay changed to call _cancel
somewhere. I have now changed this in my local git tree here.
Ahh cool. Well that's reassuring to hear as there is a fair bit of code
that uses this approach from what I can tell.
Incidentally, can you have a quick glance over this bug for me?
https://qa.mandriva.com/show_bug.cgi?id=44925
As I said in my last comment, I'm pretty sure the problem is the abuse
of the gtk main loop (which they exit and restart) but as I'm not really
a gtk hacker I'm not too sure.
Col
--
Colin Guthrie
gmane(at)colin.guthr.ie
http://colin.guthr.ie/
Day Job:
Tribalogic Limited [http://www.tribalogic.net/]
Open Source:
Mandriva Linux Contributor [http://www.mandriva.com/]
PulseAudio Hacker [http://www.pulseaudio.org/]
Trac Hacker [http://trac.edgewall.org/]
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