[01/17] Fix and test "checkpoint" in non-stop mode

diff --git a/gdb/infrun.c b/gdb/infrun.c
index f5faa0a..01d5a34 100644
--- a/gdb/infrun.c
+++ b/gdb/infrun.c
@@ -3766,8 +3766,18 @@  handle_inferior_event (struct execution_control_state *ecs)
      any other process were left running.  */
   if (!non_stop)
     set_executing (minus_one_ptid, 0);
-  else if (ecs->ws.kind != TARGET_WAITKIND_SIGNALLED
-	   && ecs->ws.kind != TARGET_WAITKIND_EXITED)
+  else if (ecs->ws.kind == TARGET_WAITKIND_SIGNALLED
+	   && ecs->ws.kind == TARGET_WAITKIND_EXITED)
+    {
+      ptid_t pid_ptid;
+
+      /* Some targets still have execution when a process exits.
+	 E.g., for "checkpoint", when when a fork exits and is
+	 mourned, linux-fork.c switches to another fork.  */
+      pid_ptid = pid_to_ptid (ptid_get_pid (ecs->ptid));
+      set_executing (pid_ptid, 0);
+    }
+  else
     set_executing (ecs->ptid, 0);
 
   switch (ecs->ws.kind)
@@ -6506,6 +6516,7 @@  normal_stop (void)
   struct target_waitstatus last;
   ptid_t last_ptid;
   struct cleanup *old_chain = make_cleanup (null_cleanup, NULL);
+  ptid_t pid_ptid;
 
   get_last_target_status (&last_ptid, &last);
 
@@ -6515,9 +6526,19 @@  normal_stop (void)
      here, so do this before any filtered output.  */
   if (!non_stop)
     make_cleanup (finish_thread_state_cleanup, &minus_one_ptid);
-  else if (last.kind != TARGET_WAITKIND_SIGNALLED
-	   && last.kind != TARGET_WAITKIND_EXITED
-	   && last.kind != TARGET_WAITKIND_NO_RESUMED)
+  else if (last.kind == TARGET_WAITKIND_SIGNALLED
+	   || last.kind == TARGET_WAITKIND_EXITED)
+    {
+      /* Some targets still have execution when a process exits.
+	 E.g., for "checkpoint", when when a fork exits and is
+	 mourned, linux-fork.c switches to another fork.  */
+      if (!ptid_equal (inferior_ptid, null_ptid))
+	{
+	  pid_ptid = pid_to_ptid (ptid_get_pid (inferior_ptid));
+	  make_cleanup (finish_thread_state_cleanup, &pid_ptid);
+	}
+    }
+  else if (last.kind != TARGET_WAITKIND_NO_RESUMED)
     make_cleanup (finish_thread_state_cleanup, &inferior_ptid);
 
   /* As we're presenting a stop, and potentially removing breakpoints,
diff --git a/gdb/testsuite/gdb.base/checkpoint-ns.exp b/gdb/testsuite/gdb.base/checkpoint-ns.exp
new file mode 100644
index 0000000..03a1747
--- /dev/null
+++ b/gdb/testsuite/gdb.base/checkpoint-ns.exp
@@ -0,0 +1,27 @@ 
+# Copyright 2015 Free Software Foundation, Inc.
+
+# This program is free software; you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation; either version 3 of the License, or
+# (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
+
+# Test gdb checkpoint and restart in non-stop mode.
+
+# We drive non-stop mode from a separate file because the whole test
+# takes a while to run.  This way, we can test both modes in parallel.
+
+# checkpoint.exp reads this variable.
+set checkpoint_non_stop 1
+
+source $srcdir/$subdir/checkpoint.exp
+
+# Unset to avoid problems with non-parallel mode.
+unset checkpoint_non_stop
diff --git a/gdb/testsuite/gdb.base/checkpoint.exp b/gdb/testsuite/gdb.base/checkpoint.exp
index 6d94ab6..c297b50 100644
--- a/gdb/testsuite/gdb.base/checkpoint.exp
+++ b/gdb/testsuite/gdb.base/checkpoint.exp
@@ -13,6 +13,20 @@ 
 # You should have received a copy of the GNU General Public License
 # along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
 
+#
+# This tests gdb checkpoint and restart.
+#
+
+# Note this file is also sourced by checkpoint-ns.exp to run all the
+# tests below in non-stop mode.  That's driven by a separate file so
+# testing both all-stop and non-stop can be done in parallel.
+
+# This is the variable checkpoint-ns.exp sets to request non-stop
+# mode.  When not set, default to all-stop mode.
+if {![info exists checkpoint_non_stop]} {
+    set checkpoint_non_stop 0
+}
+
 if { [is_remote target] || ![isnative] } then {
     continue
 }
@@ -24,8 +38,10 @@  if {![istarget "*-*-linux*"]} then {
     continue
 }
 
-
-standard_testfile .c
+# Must name the source file explicitly, otherwise when driven by
+# checkpoints-ns.exp, we'd try compiling checkpoints-ns.c, which
+# doesn't exist.
+standard_testfile checkpoint.c
 
 set pi_txt [gdb_remote_download host ${srcdir}/${subdir}/pi.txt]
 if {[is_remote host]} {
@@ -42,9 +58,9 @@  if {[prepare_for_testing ${testfile}.exp $testfile $srcfile \
 
 global gdb_prompt
 
-#
-# This tests gdb checkpoint and restart.
-#
+if {$checkpoint_non_stop} {
+    gdb_test_no_output "set non-stop on"
+}
 
 runto_main
 set break1_loc [gdb_get_line_number "breakpoint 1"]
@@ -327,6 +343,11 @@  gdb_start
 gdb_reinitialize_dir $srcdir/$subdir
 gdb_load ${binfile}
 
+if {$checkpoint_non_stop} {
+    gdb_test_no_output "set non-stop on" \
+	"set non-stop on, for many checkpoints"
+}
+
 runto_main
 gdb_breakpoint $break1_loc
 
diff --git a/gdb/thread.c b/gdb/thread.c
index ec398f5..db631c9 100644
--- a/gdb/thread.c
+++ b/gdb/thread.c
@@ -1266,8 +1266,16 @@  restore_selected_frame (struct frame_id a_frame_id, int frame_level)
     }
 }
 
+/* Data used by the cleanup installed by
+   'make_cleanup_restore_current_thread'.  */
+
 struct current_thread_cleanup
 {
+  /* Next in list of currently installed 'struct
+     current_thread_cleanup' cleanups.  See
+     'current_thread_cleanup_chain' below.  */
+  struct current_thread_cleanup *next;
+
   ptid_t inferior_ptid;
   struct frame_id selected_frame_id;
   int selected_frame_level;
@@ -1276,6 +1284,29 @@  struct current_thread_cleanup
   int was_removable;
 };
 
+/* A chain of currently installed 'struct current_thread_cleanup'
+   cleanups.  Restoring the previously selected thread looks up the
+   old thread in the thread list by ptid.  If the thread changes ptid,
+   we need to update the cleanup's thread structure so the look up
+   succeeds.  */
+static struct current_thread_cleanup *current_thread_cleanup_chain;
+
+/* A thread_ptid_changed observer.  Update all currently installed
+   current_thread_cleanup cleanups that want to switch back to
+   OLD_PTID to switch back to NEW_PTID instead.  */
+
+static void
+restore_current_thread_ptid_changed (ptid_t old_ptid, ptid_t new_ptid)
+{
+  struct current_thread_cleanup *it;
+
+  for (it = current_thread_cleanup_chain; it != NULL; it = it->next)
+    {
+      if (ptid_equal (it->inferior_ptid, old_ptid))
+	it->inferior_ptid = new_ptid;
+    }
+}
+
 static void
 do_restore_current_thread_cleanup (void *arg)
 {
@@ -1316,6 +1347,8 @@  restore_current_thread_cleanup_dtor (void *arg)
   struct thread_info *tp;
   struct inferior *inf;
 
+  current_thread_cleanup_chain = current_thread_cleanup_chain->next;
+
   tp = find_thread_ptid (old->inferior_ptid);
   if (tp)
     tp->refcount--;
@@ -1349,6 +1382,9 @@  make_cleanup_restore_current_thread (void)
   old->inf_id = current_inferior ()->num;
   old->was_removable = current_inferior ()->removable;
 
+  old->next = current_thread_cleanup_chain;
+  current_thread_cleanup_chain = old;
+
   if (!ptid_equal (inferior_ptid, null_ptid))
     {
       old->was_stopped = is_stopped (inferior_ptid);
@@ -1803,4 +1839,6 @@  Show printing of thread events (such as thread start and exit)."), NULL,
          &setprintlist, &showprintlist);
 
   create_internalvar_type_lazy ("_thread", &thread_funcs, NULL);
+
+  observer_attach_thread_ptid_changed (restore_current_thread_ptid_changed);
 }