[PATCH 19/31] Implement GDB_THREAD_OPTION_EXIT support for native Linux

Pedro Alves
2022-12-12T20:33:06Z

This implements support for the new GDB_THREAD_OPTION_EXIT thread
option for native Linux.

Change-Id: Ia69fc0b9b96f9af7de7cefc1ddb1fba9bbb0bb90
Bug: https://sourceware.org/bugzilla/show_bug.cgi?id=27338
---
gdb/linux-nat.c | 44 +++++++++++++++++++++++++++++++-------------
1 file changed, 31 insertions(+), 13 deletions(-)

diff --git a/gdb/linux-nat.c b/gdb/linux-nat.c
index b576ce60b75..75f81edf20a 100644
--- a/gdb/linux-nat.c
+++ b/gdb/linux-nat.c
@@ -269,6 +269,18 @@ pending_status_str (lwp_info *lp)
return status_to_str (lp->status);
}

+/* Return true if we should report exit events for LP. */
+
+static bool
+report_exit_events_for (lwp_info *lp)
+{
+ thread_info *thr = find_thread_ptid (linux_target, lp->ptid);
+ gdb_assert (thr != nullptr);
+
+ return (report_thread_events
+ || (thr->thread_options () & GDB_THREAD_OPTION_EXIT) != 0);
+}
+
\f
/* LWP accessors. */

@@ -2131,8 +2143,7 @@ wait_lwp (struct lwp_info *lp)
/* Check if the thread has exited. */
if (WIFEXITED (status) || WIFSIGNALED (status))
{
- if (report_thread_events
- || lp->ptid.pid () == lp->ptid.lwp ())
+ if (report_exit_events_for (lp) || is_leader (lp))
{
linux_nat_debug_printf ("LWP %d exited.", lp->ptid.pid ());

@@ -2913,7 +2924,7 @@ linux_nat_filter_event (int lwpid, int status)
/* Check if the thread has exited. */
if (WIFEXITED (status) || WIFSIGNALED (status))
{
- if (!report_thread_events && !is_leader (lp))
+ if (!report_exit_events_for (lp) && !is_leader (lp))
{
linux_nat_debug_printf ("%s exited.",
lp->ptid.to_string ().c_str ());
@@ -3123,10 +3134,11 @@ check_zombie_leaders (void)
}
}

-/* Convenience function that is called when the kernel reports an exit
- event. This decides whether to report the event to GDB as a
- process exit event, a thread exit event, or to suppress the
- event. */
+/* Convenience function that is called when we're about to return an
+ event to the core. If the event is an exit or signalled event,
+ then this decides whether to report it as process-wide event, as a
+ thread exit event, or to suppress it. All other event kinds are
+ passed through unmodified. */

static ptid_t
filter_exit_event (struct lwp_info *event_child,
@@ -3134,9 +3146,17 @@ filter_exit_event (struct lwp_info *event_child,
{
ptid_t ptid = event_child->ptid;

+ /* Note we must filter TARGET_WAITKIND_SIGNALLED as well, otherwise
+ if a non-leader thread exits with a signal, we'd report it to the
+ core which would interpret it as the whole-process exiting.
+ There is no TARGET_WAITKIND_THREAD_SIGNALLED event kind. */
+ if (ourstatus->kind () != TARGET_WAITKIND_EXITED
+ && ourstatus->kind () != TARGET_WAITKIND_SIGNALLED)
+ return ptid;
+
if (!is_leader (event_child))
{
- if (report_thread_events)
+ if (report_exit_events_for (event_child))
{
ourstatus->set_thread_exited (0);
/* Delete lwp, but not thread_info, infrun will need it to
@@ -3369,10 +3389,7 @@ linux_nat_wait_1 (ptid_t ptid, struct target_waitstatus *ourstatus,
else
lp->core = linux_common_core_of_thread (lp->ptid);

- if (ourstatus->kind () == TARGET_WAITKIND_EXITED)
- return filter_exit_event (lp, ourstatus);
-
- return lp->ptid;
+ return filter_exit_event (lp, ourstatus);
}

/* Resume LWPs that are currently stopped without any pending status
@@ -4479,7 +4496,8 @@ linux_nat_target::thread_events (int enable)
bool
linux_nat_target::supports_set_thread_options (gdb_thread_options options)
{
- constexpr gdb_thread_options supported_options = GDB_THREAD_OPTION_CLONE;
+ constexpr gdb_thread_options supported_options
+ = GDB_THREAD_OPTION_CLONE | GDB_THREAD_OPTION_EXIT;
return ((options & supported_options) == options);
}

--
2.36.0