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

Andrew Burgess via Gdb-patches
2023-06-08T12:27:55Z

Pedro Alves <pedro@palves.net> writes:

> 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.

LGTM.

Reviewed-By: Andrew Burgess <aburgess@redhat.com>

Thanks,
Andrew

>
> 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