[Qemu-devel] SDL audio and AIO hogging each other's signals

[andrzej zaborowski]

Hi,
 with QEMU_AUDIO_DRV set to "sdl" and booting from CD-ROM with AIO on
a Linux host and with SDL 1.2.11, qemu locks up in sigwait() (the main
thread) and SDL_SemWait() (the audio thread) as soon as music is
playing and CD-ROM is being read at the same time. It appears that
audio/sdlaudio.c:sdl_callback is called by SDL when it shouldn't be
called, and block-raw.c is trying to flush the AIO operations, so it
would seem that the SIGUSR2 which is intended to wake up the sigwait
is instead captured by SDL and SDL tries to be smart and calls
sdl_callback. sdl_callback has a sanity check but this check is
*after* SDL_SemWait() so it is not triggered. The strange thing is
that using a different signal (tried SIGUSR1 and SIGPOLL) for AIO
doesn't help. Does SDL catch all signals?
I could be totally wrong because I don't know SDLAudio at all.

Any ideas about the exact reason why this is happening and how to fix it?

Regards,
Andrew