Re: RFC: Unify the GNU/Linux native targets

[Michael Snyder <msnyder at redhat dot com>]

Daniel Jacobowitz wrote:
> A wart I've been meaning to come back to for ages; I have some fixes for
> thread debugging in static binaries that would have been quite ugly
> without this, so I took a day to do it.
>
> There are two target vectors in the current incarnation of linux-nat.c.  The
> one returned by linux_target () and inherited by target-specific files is
> used for non-threaded applications; it handles basic operations including
> target-specific extensions to them.  The one built in linux_nat_ops
> handles clone and can be used with libthread_db, and delegates to the
> single-threaded variant for basic tasks.
>
> This is a bit silly :-)  We still need the separation between single and
> multi-threaded vectors for the moment, because targets want to override
> the single-threaded primitives rather than the complex multi-threaded
> layer.  However, that's all we need the single-threaded vector for.  We
> don't ever need to _use_ it.
>
> This patch kills most of the single-threaded vector and arranges to
> use the multi-threaded version in all cases.  Some duplicated code
> goes away, and it is suddenly much easier to switch back and forth
> between "threaded" and "non-threaded" debugging.
>
> One oddity: the Linux native target remains at process_stratum even
> though it supports threads.  I think this is right; the thread_stratum
> gets used for linux-thread-db.c support which delegates to the process
> stratum.  If we had arbitrary stacking instead of strata I might
> stack the linux multithreaded bits above the linux single-threaded
> bits, but I think this is more natural.
>
> Tested on x86_64-pc-linux-gnu.  Any comments?  Seems like progress?
>
> Depends on my previous linux-fork.c patch, but only trivially.

Daniel, this seems fairly sane, at least with respect to forks.
It does touch code that is also touched by my recent patch,
though, so merge carefully.   ;-)

This, for instance,

+
+  /* First cut -- let's crudely do everything inline.  */
+  if (forks_exist_p ())
+    {
+      linux_fork_killall ();
+      pop_target ();
+      generic_mourn_inferior ();
+      return;
+    }
+
   /* Kill all LWP's ...  */

would want to be modified so as to read something like:

	linux_fork_killall ();
	target_mourn_inferior ();
	return;

(I think...)