Re: Inadvertently run inferior threads

[Eli Zaretskii <eliz at gnu dot org>]

[I'm taking this to gdb-patches@, as I'm suggesting a patch.]

> Date: Wed, 10 Jun 2015 18:50:13 +0300
> From: Eli Zaretskii <eliz@gnu.org>
> Cc: gdb@sourceware.org
> 
> So 'set_running' is called, and it is called with minus_one_ptid,
> which then has the effect of marking all the threads as running.
> 
> What I don't understand is why doesn't the breakpoint we set at exit
> from the inferior function countermand that.  I do see the effect of
> that breakpoint if I turn on infrun debugging:
> 
>   infrun: target_wait (-1, status) =
>   infrun:   4608 [Thread 4608.0x4900],
>   infrun:   status->kind = stopped, signal = GDB_SIGNAL_TRAP
>   infrun: TARGET_WAITKIND_STOPPED
>   infrun: stop_pc = 0x88ba9f
>   infrun: BPSTAT_WHAT_STOP_SILENT
>   infrun: stop_waiting
> 
> Why don't we mark all threads as stopped when we hit the breakpoint?
> is that because of #3 above?

Answering myself: yes.

> Any ideas how to solve this annoying problem?

One idea is implemented in the patch below.  I tested it in a
MinGW-compiled GDB doing native debugging, and it completely solved
the problem for me: I see additional threads started during an
infcall, but none of those dreaded "the selected thread is running"
error messages.

OK to commit (with a suitable ChangeLog entry)?

--- gdb/infrun.c~0	2015-01-13 15:14:47 +0200
+++ gdb/infrun.c	2015-06-11 07:13:54 +0300
@@ -6508,8 +6508,14 @@ normal_stop (void)
      running, all without informing the user/frontend about state
      transition changes.  If this is actually a call command, then the
      thread was originally already stopped, so there's no state to
-     finish either.  */
-  if (target_has_execution && inferior_thread ()->control.in_infcall)
+     finish either.  Howevever, if target doesn't support asynchronous
+     execution, we must mark all of its threads as stopped, because
+     that's what such targets do when the thread running in an infcall
+     stops.  (The cleanup will call finish_thread_state with
+     minus_one_ptid in that case.)  */
+  if (target_has_execution
+      && inferior_thread ()->control.in_infcall
+      && target_can_async_p ())
     discard_cleanups (old_chain);
   else
     do_cleanups (old_chain);