Subject: pkg/23571: devel/pth is unable to read audio device in various packages
To: None <email@example.com>
From: None <Michal@pr93.lublin.sdi.tpnet.pl,>
Date: 11/25/2003 21:08:29
>Synopsis: devel/pth is unable to read audio device in various packages
>Arrival-Date: Tue Nov 25 21:16:00 UTC 2003
>Originator: Michal Pasternak
>Release: NetBSD 1.6.1
Good People With Bad Reputation
System: NetBSD mainframe.w.lub.pl 1.6.1 NetBSD 1.6.1 (GENERIC) #0: Tue Apr 8 12:05:52 UTC 2003 firstname.lastname@example.org:/autobuild/netbsd-1-6/i386/OBJ/autobuild/netbsd-1-6/src/sys/arch/i386/compile/GENERIC i386
devel/pth is GNU Lightweight Threads package, working mainly as
a replacement layer for POSIX thread.
On NetBSD-1.6.1 at the time of writing it is unable to read
/dev/audio . I don't know about the underlying cause, but it
could mean it is unable to read other special files as well.
It could also mean a bug in underlying layers (libc?)
The problem results in unability to record sound in packages
like audio/sweep, wip/portaudio, wip/py-fastaudio, lang/python23-pth,
lang/python22-pth and propably many other packages.
1) install one of above packages
2) try to record sound.
Python's proof of concept:
- we'll use this simple one-liner to demonstrate the bug:
- on non-pth Python (I have used 2.0.1):
Python 2.0.1 (#1, Nov 25 2003, 21:42:48)
>>> open("/dev/audio", "rb").read(10)
- it reads the static. Good!
- on a Pth-enabled Python you will wait for this read _forever_
Fix is _crazy_, but first let me talk for a minute.
All GNU Pth programs that utilize Pthread simulation are in
reality a "standard", single-thread, event-driven applications.
GNU Pth uses re-defined blocking functions, as you can easy
check by running:
grep pthread_read /usr/pkg/include/pthread.h
Substituted read function (in reality, pthread_read) is declared
in pth_high.c .
I have debugged this and found out, that all programs stop
at pth_high.c:788 , in pth_wait.
This stop is either caused by bad event mask set in pth_high.c:785
(and no, adding PTH_EVENT_FD_EXCEPTION didn't help at all), or -
pth_event has some bugs, which occur while using /dev/audio .
The thing, that helps is... adding PTH_UNTIL_FD_WRITEABLE in
pth_high.c at line 785 .
And, guess what? Sweep allows me to record my freestyle raps, I can
finally write my Python VoIP software with py-fastaudio, everyone
Send patch, you say.
Someone with bigger knowledge than mine could write up a patch
for this . First, you need to check if it's only /dev/audio, or
does it hit other devices as well . Second, we need to create
a patch, that will apply only to devices, which are handled
in a broken (blocking) way by Pth. And no, testing by fstat(2)
in pth_high.c if the fd is a device won't give you proper results
(it seems it can read other "devices" without blocking)