signaling unix threads

[Jukka Heinonen]

Markus Amsler wrote:
> There's a fundamental bug in winedos/dosvm. c[1]. SIGUSR2 is sent to the 
> current process, but it should be sent to the dosvm thread. This causes 
> various ugly bugs.
> I found no way signaling a unix thread, without modifing the wineserver. 
> I have implemented a thread_kill command in the wineserver, this solves 
> my problem, but i'm quite sure it won't get applied.
>
> I'm really not a wineserver/threading expert. Have I missed something?

Yep. If using Linux 2.6 kernel and recent pthread library,
threads share the same pid and they must be signalled using
tkill and not kill. The only place which knows how to
correctly signal threads is send_thread_signal function in
server/ptrace.c. So, the easy way to fix signalling is
to use Windows thread identifier for identifying dosvm thread
instead of pids (which don't work anyway) and add to wineserver
a handler that just calls send_thread_signal, which I guess
is what you have been doing, anyway.

Now, I have tried this approach and it seems to work. I have
some prototype implementation lying around but I was thinking
about doing something more complicated at the time,
like using SIGUSR2 handler for doing Win32 remote operations
discussed earlier on wine-devel, because signal handler 
is probably running in the correct context for doing
this kind of things but I guess locking issues are going to
be pretty complicated so it is probably better to just fix
dosvm issues with a simple mechanism and not worry about
anything else.

So, feel free to submit a patch, if it is simple enough
it should get accepted or at least you should get some
suggestions how to change the patch in order for it to
get accepted.

-- 
Jukka Heinonen <http://www.iki.fi/jhei>