gdb and linuxthreads (A deadlock in linuxthreads.)

[H.J. Lu]

> 
> > Can we use another signal for gdb to indicate a new thread is created?
> > We have RT signal in linux 2.1. It should work. We can fall back to
> > __pthread_sig_cancel if RT signal is not available.
> 
> Of course, it would be best to have a third signal.  With RT signals,
> that's no problem.  But if you're running on a 2.0 kernel, there
> aren't many spare signals to use...  Your fallback plan is fine
> provided the two-signal solution still works for those poor 2.0 users.
> 

I think it is doable. We have

kernel		glibc		# of signals 		gdb
-------------------------------------------------------------
2.0		2.0		2			work
2.0		2.1		2			doesn't work
2.1		2.0		2			work
2.1		2.1		3			work.

The only case gdb doesn't is glibc 2.1 under linux 2.0 due to
__pthread_sig_cancel. I think it is ok. If you can modify
Linuxthreads, I will take care of gdb.

BTW, CLONE_PTRACE breaks gdb.

Thanks.


-- 
H.J. Lu (hjl@gnu.org)