[prev in list] [next in list] [prev in thread] [next in thread] 

List:       xine-devel
Subject:    Re: [xine-devel] xine lockups with ntpl
From:       Miguel Freitas <miguel () cetuc ! puc-rio ! br>
Date:       2003-03-07 15:30:34
[Download RAW message or body]

Hi Bastien, Ewald,

On Fri, 2003-03-07 at 06:51, Bastien Nocera wrote:
> > > NTPL shows quite a lot of bugs in programs not using threads and locks
> > > carefully enough, apparently.
> > >
> > > Anybody has an idea ?
> > 
> > I have noticed this too after installing the latest Red Hat beta (Phoebe-3). 
> > This seems to be caused by a bug in NPTL, where a condition broadcast is 
> > lost. You can use the attached patch to be able to use (and improve :)) xine. 
> > This should avoid at least the most common lockup in the xine library.
> 
> I've been chasing this with Jakub Jelinek and it could be a problem with
> the way xine expects condvars to behave which work with LinuxThreads and
> not NTPL (NTPL tries to implement the spec[1] exactly). Or it could be a
> bug in NTPL (Python threading has some problems as well with condvars).

i read again the reference you sent on threads spec and i really think
we are not doing anything wrong. it really seems to be a bug in NPTL, as
Ewald said, that pthread_cond_broadcast() may not be unblocking _ALL_
waiting threads as the spec demands.

a simple test case for it would be trying the broadcast behaviour
extensively. let two or three threads wait on the same cond and test if
all of them are unblocked with a single broadcast.

otoh, Ewald's solution is pretty nice because it also make xine more
robust on broken implementations. since it should have no side effects i
would suggest commiting it. note: also notice that audio_decoder and
video_decoder may be waiting on the same cond so they should also use a
timed wait imho.

regards,

Miguel



-------------------------------------------------------
This SF.net email is sponsored by: Etnus, makers of TotalView, The debugger 
for complex code. Debugging C/C++ programs can leave you feeling lost and 
disoriented. TotalView can help you find your way. Available on major UNIX 
and Linux platforms. Try it free. www.etnus.com
_______________________________________________
xine-devel mailing list
xine-devel@lists.sourceforge.net
https://lists.sourceforge.net/lists/listinfo/xine-devel
[prev in list] [next in list] [prev in thread] [next in thread]