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Re: [PATCH][PR guile/17247] Block SIGCHLD while initializing Guile
- From: Gary Benson <gbenson at redhat dot com>
- To: Doug Evans <xdje42 at gmail dot com>
- Cc: Eli Zaretskii <eliz at gnu dot org>, "gdb-patches at sourceware dot org" <gdb-patches at sourceware dot org>, guile-devel <guile-devel at gnu dot org>
- Date: Mon, 1 Sep 2014 13:48:40 +0100
- Subject: Re: [PATCH][PR guile/17247] Block SIGCHLD while initializing Guile
- Authentication-results: sourceware.org; auth=none
- References: <m31trwv5o1 dot fsf at sspiff dot org> <834mwsh2nu dot fsf at gnu dot org> <CAP9bCMTNsoi6AhQxJtzjc6=o9iHi8TXkX32OiKbArAuAnsjZUQ at mail dot gmail dot com>
Doug Evans wrote:
> On Sun, Aug 31, 2014 at 12:36 PM, Eli Zaretskii <firstname.lastname@example.org> wrote:
> > > From: Doug Evans <email@example.com>
> > > Date: Sun, 31 Aug 2014 12:07:58 -0700
> > >
> > > Basically, current Guile (git) starts an internal thread (the
> > > "finalizer" thread), and libgc as of 7.4 now starts several
> > > marker threads by default (before 7.4.0 one needed to configure
> > > libgc with --enable-parallel-mark).
> > >
> > > When other threads are running, and they haven't blocked
> > > SIGCHLD, then the kernel may send SIGCHLD to these threads,
> > > leaving gdb hung in the sigsuspend calls in linux-nat.c.
> > A heretic thought: is it at all a good idea to have Guile (and GC)
> > start threads when they run under GDB? GDB is a single-threaded
> > program, so having it linked against libraries that start threads
> > whenever they like is IME a source of subtle problems (like this
> > one) and a lot of pain down the road. Anything GDB does that
> > affects the global environment of the whole program (e.g., I/O
> > redirection) will also affect those threads, with who knows what
> > consequences.
> > So maybe The Right Way of fixing these problems is configure Guile
> > and GC so that they never start any additional threads?
> Users are going to want to start threads.
> I've seen that already.
> I think we should not shy away from them.
This patch ensures the internal threads are created with SIGCHLD
blocked. Does something do this for other (user started?) threads?