[review] gdb/infrun: stop all threads if there exists a non-stop target

diff --git a/gdb/infrun.c b/gdb/infrun.c
index 3e846f8..fd72a74 100644
--- a/gdb/infrun.c
+++ b/gdb/infrun.c
@@ -4682,7 +4682,7 @@ 
   int pass;
   int iterations = 0;
 
-  gdb_assert (target_is_non_stop_p ());
+  gdb_assert (exists_non_stop_target ());
 
   if (debug_infrun)
     fprintf_unfiltered (gdb_stdlog, "infrun: stop_all_threads\n");
@@ -4713,6 +4713,18 @@ 
 	     to tell the target to stop.  */
 	  for (thread_info *t : all_non_exited_threads ())
 	    {
+	      /* For a single-target setting with an all-stop target,
+		 we would not even arrive here.  For a multi-target
+		 setting, until GDB is able to handle a mixture of
+		 all-stop and non-stop targets, simply skip all-stop
+		 targets' threads.  This should be fine due to the
+		 protection of commit
+		 2f4fcf00399bc0ad5a4fed6b530128e8be4f40da  */
+
+	      switch_to_thread_no_regs (t);
+	      if (!target_is_non_stop_p ())
+		continue;
+
 	      if (t->executing)
 		{
 		  /* If already stopping, don't request a stop again.
@@ -4724,7 +4736,6 @@ 
 					    "infrun:   %s executing, "
 					    "need stop\n",
 					    target_pid_to_str (t->ptid).c_str ());
-		      switch_to_thread_no_regs (t);
 		      target_stop (t->ptid);
 		      t->stop_requested = 1;
 		    }
@@ -7837,9 +7848,9 @@ 
   /* Let callers know we don't want to wait for the inferior anymore.  */
   ecs->wait_some_more = 0;
 
-  /* If all-stop, but the target is always in non-stop mode, stop all
+  /* If all-stop, but there exists a non-stop target, stop all
      threads now that we're presenting the stop to the user.  */
-  if (!non_stop && target_is_non_stop_p ())
+  if (!non_stop && exists_non_stop_target ())
     stop_all_threads ();
 }
 
diff --git a/gdb/testsuite/gdb.multi/stop-all-on-exit.c b/gdb/testsuite/gdb.multi/stop-all-on-exit.c
new file mode 100644
index 0000000..bca0c98
--- /dev/null
+++ b/gdb/testsuite/gdb.multi/stop-all-on-exit.c
@@ -0,0 +1,27 @@ 
+/* This testcase is part of GDB, the GNU debugger.
+
+   Copyright 2020 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/>.  */
+
+#include <unistd.h>
+
+static unsigned int duration = 1;
+
+int
+main ()
+{
+  sleep (duration);
+  return 0;
+}
diff --git a/gdb/testsuite/gdb.multi/stop-all-on-exit.exp b/gdb/testsuite/gdb.multi/stop-all-on-exit.exp
new file mode 100644
index 0000000..a0622ae
--- /dev/null
+++ b/gdb/testsuite/gdb.multi/stop-all-on-exit.exp
@@ -0,0 +1,64 @@ 
+# This testcase is part of GDB, the GNU debugger.
+
+# Copyright 2020 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 that in all-stop mode with multiple inferiors, GDB stops all
+# threads upon receiving an exit event from one of the inferiors.
+
+standard_testfile
+
+if {[prepare_for_testing "failed to prepare" $testfile $srcfile]} {
+    return -1
+}
+
+if {![runto_main]} {
+    fail "starting inferior 1"
+    return -1
+}
+
+# This is a test specific for a native target, where we use the
+# "-exec" argument to "add-inferior" and we explicitly don't do
+# "maint set target-non-stop on".
+if {![gdb_is_target_native]} {
+    untested "the test is aimed at a native target"
+    return 0
+}
+
+# Add a second inferior that will sleep longer.
+gdb_test "add-inferior -exec $binfile" "Added inferior 2.*" \
+    "add the second inferior"
+gdb_test "inferior 2" ".*Switching to inferior 2.*"
+if {![runto_main]} {
+    fail "starting inferior 2"
+    return -1
+}
+gdb_test "print duration=10" "= 10"
+
+# Now continue both processes.  We should get the exit event from the
+# first inferior.
+gdb_test_no_output "set schedule-multiple on"
+gdb_continue_to_end
+
+# GDB is expected to have stopped the other inferior.  Switch to the
+# slow inferior's thread.  It should not be running.
+gdb_test_multiple "thread 2.1" "check thread 2.1 is not running" {
+    -re ".*\\(running\\)\[\r\n\]+$gdb_prompt" {
+	fail $gdb_test_name
+    }
+    -re ".*$gdb_prompt" {
+	pass $gdb_test_name
+    }
+}