[PATCH 10/11] Ensure EXIT is last event, gdbserver/linux

[Pedro Alves <pedro@palves.net>]

Same as the previous patch, but for GDBserver.

In a nutshell, don't report exit events for the leader thread until
all pending events for other threads are flushed.

Change-Id: I3f855f48bea15a527a87565f8b9f4000169cd6c0
---
 gdbserver/linux-low.cc | 46 +++++++++++++++++++++++++++++++++---------
 gdbserver/linux-low.h  | 15 ++++++++++++--
 2 files changed, 49 insertions(+), 12 deletions(-)

diff --git a/gdbserver/linux-low.cc b/gdbserver/linux-low.cc
index 5c037881670..15c2914e444 100644
--- a/gdbserver/linux-low.cc
+++ b/gdbserver/linux-low.cc
@@ -1655,16 +1655,10 @@ lwp_resumed (struct lwp_info *lwp)
 }
 
 bool
-linux_process_target::status_pending_p_callback (thread_info *thread,
-						 ptid_t ptid)
+linux_process_target::status_pending_p (thread_info *thread)
 {
   struct lwp_info *lp = get_thread_lwp (thread);
 
-  /* Check if we're only interested in events from a specific process
-     or a specific LWP.  */
-  if (!thread->id.matches (ptid))
-    return 0;
-
   if (!lwp_resumed (lp))
     return 0;
 
@@ -1678,6 +1672,38 @@ linux_process_target::status_pending_p_callback (thread_info *thread,
   return lp->status_pending_p;
 }
 
+bool
+linux_process_target::non_leader_lwp_in_process_with_pending_event
+  (thread_info *thread)
+{
+  gdb_assert (is_leader (thread));
+
+  thread_info *found = find_thread (ptid_t (pid_of (thread)),
+				    [&] (thread_info *other)
+    {
+      return !is_leader (other) && status_pending_p (other);
+    });
+
+  return found != nullptr;
+}
+
+bool
+linux_process_target::has_reportable_pending_event (thread_info *thread,
+						    ptid_t filter_ptid)
+{
+  /* Check if we're only interested in events from a specific process
+     or a specific thread.  */
+  if (!thread->id.matches (filter_ptid))
+    return false;
+
+  lwp_info *lp = get_thread_lwp (thread);
+
+  return (status_pending_p (thread)
+	  && !(!WIFSTOPPED (lp->status_pending)
+	       && is_leader (thread)
+	       && non_leader_lwp_in_process_with_pending_event (thread)));
+}
+
 struct lwp_info *
 find_lwp_pid (ptid_t ptid)
 {
@@ -2446,7 +2472,7 @@ linux_process_target::wait_for_event_filtered (ptid_t wait_ptid,
     {
       event_thread = find_thread_in_random ([&] (thread_info *thread)
 	{
-	  return status_pending_p_callback (thread, filter_ptid);
+	  return has_reportable_pending_event (thread, filter_ptid);
 	});
 
       if (event_thread != NULL)
@@ -2562,7 +2588,7 @@ linux_process_target::wait_for_event_filtered (ptid_t wait_ptid,
 	 any.  */
       event_thread = find_thread_in_random ([&] (thread_info *thread)
 	{
-	  return status_pending_p_callback (thread, filter_ptid);
+	  return has_reportable_pending_event (thread, filter_ptid);
 	});
 
       if (event_thread != NULL)
@@ -2902,7 +2928,7 @@ linux_process_target::wait_1 (ptid_t ptid, target_waitstatus *ourstatus,
 
   auto status_pending_p_any = [&] (thread_info *thread)
     {
-      return status_pending_p_callback (thread, minus_one_ptid);
+      return status_pending_p (thread);
     };
 
   auto not_stopped = [&] (thread_info *thread)
diff --git a/gdbserver/linux-low.h b/gdbserver/linux-low.h
index 27cc9641f12..bd71e673871 100644
--- a/gdbserver/linux-low.h
+++ b/gdbserver/linux-low.h
@@ -483,8 +483,19 @@ class linux_process_target : public process_stratum_target
      they should be re-issued if necessary.  */
   void resume_one_thread (thread_info *thread, bool leave_all_stopped);
 
-  /* Return true if this lwp has an interesting status pending.  */
-  bool status_pending_p_callback (thread_info *thread, ptid_t ptid);
+  /* Return true if THREAD has an interesting status pending.  */
+  bool status_pending_p (thread_info *thread);
+
+  /* Return true if another thread of the same process as THREAD has a
+     pending status ready to be processed.  THREAD is assumed to be
+     the leader of its process.  */
+  bool non_leader_lwp_in_process_with_pending_event (thread_info *thread);
+
+  /* Indicate if THREAD has a pending event which should be considered
+     for immediate processing.  Only threads that match FILTER_PTID
+     are considered.  Does not consider a leader thread's exit event
+     before the non-leader threads have reported their exits.  */
+  bool has_reportable_pending_event (thread_info *thread, ptid_t filter_ptid);
 
   /* Resume LWPs that are currently stopped without any pending status
      to report, but are resumed from the core's perspective.  */
-- 
2.26.2