On Wed, 4 Apr 2007, andrzej zaborowski wrote:
Hi, thanks for quick response!
On 03/04/07, malc <[EMAIL PROTECTED]> wrote:
On Tue, 3 Apr 2007, andrzej zaborowski wrote:
[..snip..]
It should be using ALSA.
Here's my theory: signal will be delivered to the arbitrary thread
that happens to not block it, for whatever reason, the thread SDL
created to do audio processing is picked up, which leads to some
system call being interrupted(eventually) and -1 (errno == EINTR), SDL
happily continues calling stuff.
Actually the signal can be just handled (by whatever signal handler
QEMU installed with sigaction) in a SDL created thread, so things can,
and mostlikely will, be silently wrong, i.e. EINTR while possible will
not necessarily happen.
Yes, reading the PTHREAD_SIGNAL(3) note, this sounds very likely.
One solution would be to explicitly block everything upon entering
sdl_callback for the first time. This is ugly and can have any
consequences one cares to imagine, but that's SDL for you (any
particular reason why you are using it?)
Not really - just had only OSS and SDL compiled into qemu at this moment.
Yes, the suggested solution works. Unfortunately it's neither pretty
nor correct, because at the time sdl_callback runs, the signal which
was supposed to wake up sigwait() is already lost and I can't find any
way to prevent that - we can add a kill(0, SIGUSR2) but this is even
uglier and again we don't know when sdl_callback is called as a result
of this signal and when legally. (That's also why I didn't put a
"return" after pthread_sigmask().)
[..snip..]
What POSIX needs is a way to set the default signal mask for new threads :-/
http://www.opengroup.org/onlinepubs/007908799/xsh/pthread_create.html
in part reads
<quote>
The signal state of the new thread is initialised as follows:
* The signal mask is inherited from the creating thread.
</quote>
Hence sequence of:
sigfillset (newset)
pthread_sigmask (SIG_BLOCK, newset, oldset)
SDL_OpenAudio (...)
pthread_sigmask (SGI_SETMASK, oldset, NULL)
Will probably achieve the desired effect.
--
vale
