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PR threads/18127 - threads spawned by infcall end up stuck in "running" state

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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.
This commit is contained in:
Pedro Alves
2015-06-29 16:07:57 +01:00
parent 2880b51c25
commit 28bf096c62
6 changed files with 148 additions and 18 deletions
Download Patch File Download Diff File Expand all files Collapse all files

31
gdb/infrun.c
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@@ -2264,11 +2264,8 @@ resume (enum gdb_signal sig)
requests finish. The thread is not executing at this
point, and the call to set_executing will be made later.
But we need to call set_running here, since from the
user/frontend's point of view, threads were set running.
Unless we're calling an inferior function, as in that
case we pretend the inferior doesn't run at all. */
if (!tp->control.in_infcall)
set_running (user_visible_resume_ptid (user_step), 1);
user/frontend's point of view, threads were set running. */
set_running (user_visible_resume_ptid (user_step), 1);
discard_cleanups (old_cleanups);
return;
}
@@ -2346,10 +2343,8 @@ resume (enum gdb_signal sig)
/* Even if RESUME_PTID is a wildcard, and we end up resuming less
(e.g., we might need to step over a breakpoint), from the
user/frontend's point of view, all threads in RESUME_PTID are now
running. Unless we're calling an inferior function, as in that
case pretend we inferior doesn't run at all. */
if (!tp->control.in_infcall)
set_running (resume_ptid, 1);
running. */
set_running (resume_ptid, 1);
/* Maybe resume a single thread after all. */
if ((step || thread_has_single_step_breakpoints_set (tp))
@@ -6664,15 +6659,15 @@ normal_stop (void)
if (has_stack_frames () && !stop_stack_dummy)
set_current_sal_from_frame (get_current_frame ());
/* Let the user/frontend see the threads as stopped, but do nothing
if the thread was running an infcall. We may be e.g., evaluating
a breakpoint condition. In that case, the thread had state
THREAD_RUNNING before the infcall, and shall remain set to
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)
/* Let the user/frontend see the threads as stopped, but defer to
call_function_by_hand if the thread finished an infcall
successfully. We may be e.g., evaluating a breakpoint condition.
In that case, the thread had state THREAD_RUNNING before the
infcall, and shall remain marked running, all without informing
the user/frontend about state transition changes. */
if (target_has_execution
&& inferior_thread ()->control.in_infcall
&& stop_stack_dummy == STOP_STACK_DUMMY)
discard_cleanups (old_chain);
else
do_cleanups (old_chain);