Re: [patch] linux_nat_kill() compat. with linux-2.4.x

[Jan Kratochvil <jan dot kratochvil at redhat dot com>]

On Wed, 21 May 2014 14:49:43 +0200, Pedro Alves wrote:
> On 03/16/2014 01:59 PM, Jan Kratochvil wrote:
> > diff --git a/gdb/linux-nat.c b/gdb/linux-nat.c
> > index b615423..ec84188 100644
> > --- a/gdb/linux-nat.c
> > +++ b/gdb/linux-nat.c
> > @@ -3777,8 +3777,15 @@ linux_nat_kill (struct target_ops *ops)
> >      {
> >        ptid_t ptid = pid_to_ptid (ptid_get_pid (inferior_ptid));
> >  
> > +      /* Kill all LWP's before trying to stop them.  In rare cases the
> > +	 lwp_info state may not match the inferior and
> > +	 stop_wait_callback could lock up.  */
> 
> Hmm, I find this comment confusing and not really enlightening.
> What sort of rare cases?  It that PR15713?  Best just fix that.
> I've sent a patch:
> https://sourceware.org/ml/gdb-patches/2014-05/msg00473.html

The reproducible case is that PR15713 and it is sure great you have fixed it.

Fine with dropping the patch although I still do not find it obvious the patch
is no longer relevant.

FSF GDB now relies on fact that ptraced inferior state always matches
lp->stopped and there is a matching signal to wait for etc.  In some cases GDB
hangs during quit (and inferiors cleanup) and one has to kill GDB itself.
Reasons are not known to me as I do not know how to reproduce it.
(It may be also possible all such reasons have been fixed now.)
It also may hang somewhere else and not in linux_nat_kill().

This patch made GDB foolproof against any state of inferior when killing the
inferior so that GDB could no longer hang.  But it would hide some possible
remaining bugs in the code (which may be causing the GDB hangs).


Jan