[PATCH 16/31] Move deleting thread on TARGET_WAITKIND_THREAD_EXITED to core

Pedro Alves
2022-12-12T20:33:53Z

Currently, infrun assumes that when TARGET_WAITKIND_THREAD_EXITED is
reported, the corresponding GDB thread has already been removed from
the GDB thread list.

Later in the series, that will no longer work, as infrun will need to
refer to the thread's thread_info when it processes
TARGET_WAITKIND_THREAD_EXITED.

As preparation, this patch makes deleting the GDB thread
responsibility of infrun, instead of the target.

Change-Id: I013d87f61ffc9aaca49f0d6ce2a43e3ea69274de
---
gdb/infrun.c | 31 ++++++++++++++++++++++++++-----
gdb/linux-nat.c | 22 +++++++++++++++-------
gdb/netbsd-nat.c | 1 -
3 files changed, 41 insertions(+), 13 deletions(-)

diff --git a/gdb/infrun.c b/gdb/infrun.c
index c100bc70034..6fdffb31884 100644
--- a/gdb/infrun.c
+++ b/gdb/infrun.c
@@ -4238,7 +4238,12 @@ reinstall_readline_callback_handler_cleanup ()
}

/* Clean up the FSMs of threads that are now stopped. In non-stop,
- that's just the event thread. In all-stop, that's all threads. */
+ that's just the event thread. In all-stop, that's all threads. In
+ all-stop, threads that had a pending exit no longer have a reason
+ to be around, as their FSMs/commands are canceled, so we delete
+ them. This avoids "info threads" listing such threads as if they
+ were alive (and failing to read their registers), the user being to
+ select and resume them (and that failing), etc. */

static void
clean_up_just_stopped_threads_fsms (struct execution_control_state *ecs)
@@ -4256,15 +4261,28 @@ clean_up_just_stopped_threads_fsms (struct execution_control_state *ecs)
{
scoped_restore_current_thread restore_thread;

- for (thread_info *thr : all_non_exited_threads ())
+ for (thread_info *thr : all_threads_safe ())
{
- if (thr->thread_fsm () == nullptr)
+ if (thr->state == THREAD_EXITED)
continue;
+
if (thr == ecs->event_thread)
continue;

- switch_to_thread (thr);
- thr->thread_fsm ()->clean_up (thr);
+ if (thr->thread_fsm () != nullptr)
+ {
+ switch_to_thread (thr);
+ thr->thread_fsm ()->clean_up (thr);
+ }
+
+ /* As we are cancelling the command/FSM of this thread,
+ whatever was the reason we needed to report a thread
+ exited event to the user, that reason is gone. Delete
+ the thread, so that the user doesn't see it in the thread
+ list, the next proceed doesn't try to resume it, etc. */
+ if (thr->has_pending_waitstatus ()
+ && thr->pending_waitstatus ().kind () == TARGET_WAITKIND_THREAD_EXITED)
+ delete_thread (thr);
}
}
}
@@ -5537,6 +5555,9 @@ handle_inferior_event (struct execution_control_state *ecs)

if (ecs->ws.kind () == TARGET_WAITKIND_THREAD_EXITED)
{
+ ecs->event_thread = find_thread_ptid (ecs->target, ecs->ptid);
+ gdb_assert (ecs->event_thread != nullptr);
+ delete_thread (ecs->event_thread);
prepare_to_wait (ecs);
return;
}
diff --git a/gdb/linux-nat.c b/gdb/linux-nat.c
index 5fadc82deb0..b576ce60b75 100644
--- a/gdb/linux-nat.c
+++ b/gdb/linux-nat.c
@@ -898,10 +898,11 @@ linux_nat_switch_fork (ptid_t new_ptid)
registers_changed ();
}

-/* Handle the exit of a single thread LP. */
+/* Handle the exit of a single thread LP. If DEL_THREAD is true,
+ delete the thread_info associated to LP, if it exists. */

static void
-exit_lwp (struct lwp_info *lp)
+exit_lwp (struct lwp_info *lp, bool del_thread = true)
{
struct thread_info *th = find_thread_ptid (linux_target, lp->ptid);

@@ -911,7 +912,8 @@ exit_lwp (struct lwp_info *lp)
gdb_printf (_("[%s exited]\n"),
target_pid_to_str (lp->ptid).c_str ());

- delete_thread (th);
+ if (del_thread)
+ delete_thread (th);
}

delete_lwp (lp->ptid);
@@ -3135,11 +3137,17 @@ filter_exit_event (struct lwp_info *event_child,
if (!is_leader (event_child))
{
if (report_thread_events)
- ourstatus->set_thread_exited (0);
+ {
+ ourstatus->set_thread_exited (0);
+ /* Delete lwp, but not thread_info, infrun will need it to
+ process the event. */
+ exit_lwp (event_child, false);
+ }
else
- ourstatus->set_ignore ();
-
- exit_lwp (event_child);
+ {
+ ourstatus->set_ignore ();
+ exit_lwp (event_child);
+ }
}

return ptid;
diff --git a/gdb/netbsd-nat.c b/gdb/netbsd-nat.c
index bbadd865823..aa16a6cc5bd 100644
--- a/gdb/netbsd-nat.c
+++ b/gdb/netbsd-nat.c
@@ -629,7 +629,6 @@ nbsd_nat_target::wait (ptid_t ptid, struct target_waitstatus *ourstatus,
if (print_thread_events)
gdb_printf (_("[%s exited]\n"),
target_pid_to_str (wptid).c_str ());
- delete_thread (thr);
}

/* The GDB core expects that the rest of the threads are running. */
--
2.36.0