Revert "gdb: remove unnecessary parameter wait_ptid from do_target_wait"

This reverts commit ac0d67e.

There was nothing wrong with the commit which I'm reverting here, but
it removed some functionality that will be needed for a later commit;
that is, the ability for GDB to ask for events from a specific ptid_t
via the do_target_wait function.

In a follow up commit, this functionality will be used to implement
inferior function calls in multi-threaded inferiors.

This is not a straight revert of the above commit.  Reverting the
above commit replaces a 'nullptr' with 'NULL', I've gone in and
changed that, preserving the 'nullptr'.

Reviewed-By: Tankut Baris Aktemur <[email protected]>
Tested-By: Luis Machado <[email protected]>
Tested-By: Keith Seitz <[email protected]>

gdb/infrun.c

@@ -4125,7 +4125,8 @@ do_target_wait_1 (inferior *inf, ptid_t ptid,
    more events.  Polls for events from all inferiors/targets.  */
 
 static bool
-do_target_wait (execution_control_state *ecs, target_wait_flags options)
+do_target_wait (ptid_t wait_ptid, execution_control_state *ecs,
+		target_wait_flags options)
 {
   int num_inferiors = 0;
   int random_selector;
@@ -4135,9 +4136,10 @@ do_target_wait (execution_control_state *ecs, target_wait_flags options)
      polling the rest of the inferior list starting from that one in a
      circular fashion until the whole list is polled once.  */
 
-  auto inferior_matches = [] (inferior *inf)
+  auto inferior_matches = [&wait_ptid] (inferior *inf)
     {
-      return inf->process_target () != nullptr;
+      return (inf->process_target () != nullptr
+	      && ptid_t (inf->pid).matches (wait_ptid));
     };
 
   /* First see how many matching inferiors we have.  */
@@ -4176,7 +4178,7 @@ do_target_wait (execution_control_state *ecs, target_wait_flags options)
 
   auto do_wait = [&] (inferior *inf)
   {
-    ecs->ptid = do_target_wait_1 (inf, minus_one_ptid, &ecs->ws, options);
+    ecs->ptid = do_target_wait_1 (inf, wait_ptid, &ecs->ws, options);
     ecs->target = inf->process_target ();
     return (ecs->ws.kind () != TARGET_WAITKIND_IGNORE);
   };
@@ -4626,7 +4628,7 @@ fetch_inferior_event ()
        the event.  */
     scoped_disable_commit_resumed disable_commit_resumed ("handling event");
 
-    if (!do_target_wait (&ecs, TARGET_WNOHANG))
+    if (!do_target_wait (minus_one_ptid, &ecs, TARGET_WNOHANG))
       {
 	infrun_debug_printf ("do_target_wait returned no event");
 	disable_commit_resumed.reset_and_commit ();