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2ab76a181f
Attaching in non-stop mode currently misbehaves, like so:
(gdb) attach 1244450
Attaching to process 1244450
[New LWP 1244453]
[New LWP 1244454]
[New LWP 1244455]
[New LWP 1244456]
[New LWP 1244457]
[New LWP 1244458]
[New LWP 1244459]
[New LWP 1244461]
[New LWP 1244462]
[New LWP 1244463]
No unwaited-for children left.
At this point, GDB's stopped/running thread state is out of sync with
the inferior:
(gdb) info threads
Id Target Id Frame
* 1 LWP 1244450 "attach-non-stop" 0xf1b443bf in ?? ()
2 LWP 1244453 "attach-non-stop" (running)
3 LWP 1244454 "attach-non-stop" (running)
4 LWP 1244455 "attach-non-stop" (running)
5 LWP 1244456 "attach-non-stop" (running)
6 LWP 1244457 "attach-non-stop" (running)
7 LWP 1244458 "attach-non-stop" (running)
8 LWP 1244459 "attach-non-stop" (running)
9 LWP 1244461 "attach-non-stop" (running)
10 LWP 1244462 "attach-non-stop" (running)
11 LWP 1244463 "attach-non-stop" (running)
(gdb)
(gdb) interrupt -a
(gdb)
*nothing*
The problem is that attaching installs an inferior continuation,
called when the target reports the initial attach stop, here, in
inf-loop.c:inferior_event_handler:
/* Do all continuations associated with the whole inferior (not
a particular thread). */
if (inferior_ptid != null_ptid)
do_all_inferior_continuations (0);
However, currently in non-stop mode, inferior_ptid is still null_ptid
when we get here.
If you try to do "set debug infrun 1" to debug the problem, however,
then the attach completes correctly, with GDB reporting a stop for
each thread.
The bug is that we're missing a switch_to_thread/context_switch call
when handling the initial stop, here:
if (stop_soon == STOP_QUIETLY_NO_SIGSTOP
&& (ecs->event_thread->suspend.stop_signal == GDB_SIGNAL_STOP
|| ecs->event_thread->suspend.stop_signal == GDB_SIGNAL_TRAP
|| ecs->event_thread->suspend.stop_signal == GDB_SIGNAL_0))
{
stop_print_frame = true;
stop_waiting (ecs);
ecs->event_thread->suspend.stop_signal = GDB_SIGNAL_0;
return;
}
Note how the STOP_QUIETLY / STOP_QUIETLY_REMOTE case above that does
call context_switch.
And the reason "set debug infrun 1" "fixes" it, is that the debug path
has a switch_to_thread call.
This patch fixes it by moving the main context_switch call earlier.
It also removes the:
if (ecs->ptid != inferior_ptid)
check at the same time because:
#1 - that is half of what context_switch already does
#2 - deprecated_context_hook is only used in Insight, and all it does
is set an int. It won't care if we call it when the current
thread hasn't actually changed.
A testcase exercising this will be added in a following patch.
gdb/ChangeLog:
PR gdb/27055
* infrun.c (handle_signal_stop): Move main context_switch call
earlier, before STOP_QUIETLY_NO_SIGSTOP.
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