[binutils-gdb] PR threads/18127 - threads spawned by infcall end up stuck in "running" state

[sergiodj+buildbot at redhat dot com]

*** TEST RESULTS FOR COMMIT 28bf096c62d7da6b349605f3940f4c586a850f78 ***

Author: Pedro Alves <palves@redhat.com>
Branch: master
Commit: 28bf096c62d7da6b349605f3940f4c586a850f78

PR threads/18127 - threads spawned by infcall end up stuck in "running" state
Refs:
 https://sourceware.org/ml/gdb/2015-03/msg00024.html
 https://sourceware.org/ml/gdb/2015-06/msg00005.html

On GNU/Linux, if an infcall spawns a thread, that thread ends up with
stuck running state.  This happens because:

 - when linux-nat.c detects a new thread, it marks them as running,
   and does not report anything to the core.

 - we skip finish_thread_state when the thread that is running the
   infcall stops.

As result, that new thread ends up with stuck "running" state, even
though it really is stopped.

On Windows, _all_ threads end up stuck in running state, not just the
one that was spawned.  That happens because when a new thread is
detected, unlike linux-nat.c, windows-nat.c reports
TARGET_WAITKIND_SPURIOUS to infrun.  It's the fact that that event
does not cause a user-visible stop that triggers the problem.  When
the target is re-resumed, we call set_running with a wildcard ptid,
which marks all thread as running.  That set_running is not suppressed
because the (leader) thread being resumed does not have in_infcall
set.  Later, when the infcall finally finishes successfully, nothing
marks all threads back to stopped.

We can trigger the same problem on all targets by having a thread
other than the one that is running the infcall report a breakpoint hit
to infrun, and then have that breakpoint not cause a stop.  That's
what the included test does.

The fix is to stop GDB from suppressing the set_running calls while
doing an infcall, and then set the threads back to stopped when the
call finishes, iff they were originally stopped before the infcall
started.  (Note the MI *running/*stopped event suppression isn't
affected.)

Tested on x86_64 GNU/Linux.

gdb/ChangeLog:
2015-06-29  Pedro Alves  <palves@redhat.com>

	PR threads/18127
	* infcall.c (run_inferior_call): On infcall success, if the thread
	was marked stopped before, reset it back to stopped.
	* infrun.c (resume): Don't suppress the set_running calls when
	doing an infcall.
	(normal_stop): Only discard the finish_thread_state cleanup if the
	infcall succeeded.

gdb/testsuite/ChangeLog:
2015-06-29  Pedro Alves  <palves@redhat.com>

	PR threads/18127
	* gdb.threads/hand-call-new-thread.c: New file.
	* gdb.threads/hand-call-new-thread.c: New file.