gdb/infrun: add inferior parameters to stop_all_threads and restart_threads

A following patch will want to stop all threads of a given inferior (as
opposed to all threads of all inferiors) while handling a vfork, and
restart them after.  To help with this, add inferior parameters to
stop_all_threads and restart_threads.  This is done as a separate patch
to make sure this doesn't cause regressions on its own, and to keep the
following patches more concise.

No visible changes are expected here, since all calls sites pass
nullptr, which should keep the existing behavior.

Change-Id: I4d9ba886ce842042075b4e346cfa64bbe2580dbf

gdb/infrun.c

@@ -3744,7 +3744,8 @@ struct wait_one_event
 };
 
 static bool handle_one (const wait_one_event &event);
-static void restart_threads (struct thread_info *event_thread);
+static void restart_threads (struct thread_info *event_thread,
+			     inferior *inf = nullptr);
 
 /* Prepare and stabilize the inferior for detaching it.  E.g.,
    detaching while a thread is displaced stepping is a recipe for
@@ -4908,7 +4909,7 @@ handle_one (const wait_one_event &event)
 /* See infrun.h.  */
 
 void
-stop_all_threads (const char *reason)
+stop_all_threads (const char *reason, inferior *inf)
 {
   /* We may need multiple passes to discover all threads.  */
   int pass;
@@ -4916,22 +4917,29 @@ stop_all_threads (const char *reason)
 
   gdb_assert (exists_non_stop_target ());
 
-  INFRUN_SCOPED_DEBUG_START_END ("reason=%s", reason);
+  INFRUN_SCOPED_DEBUG_START_END ("reason=%s, inf=%d", reason,
+				 inf != nullptr ? inf->num : -1);
 
   scoped_restore_current_thread restore_thread;
 
-  /* Enable thread events of all targets.  */
+  /* Enable thread events on relevant targets.  */
   for (auto *target : all_non_exited_process_targets ())
     {
+      if (inf != nullptr && inf->process_target () != target)
+	continue;
+
       switch_to_target_no_thread (target);
       target_thread_events (true);
     }
 
   SCOPE_EXIT
     {
-      /* Disable thread events of all targets.  */
+      /* Disable thread events on relevant targets.  */
       for (auto *target : all_non_exited_process_targets ())
 	{
+	  if (inf != nullptr && inf->process_target () != target)
+	    continue;
+
 	  switch_to_target_no_thread (target);
 	  target_thread_events (false);
 	}
@@ -4956,6 +4964,9 @@ stop_all_threads (const char *reason)
 
 	  for (auto *target : all_non_exited_process_targets ())
 	    {
+	      if (inf != nullptr && inf->process_target () != target)
+		continue;
+
 	      switch_to_target_no_thread (target);
 	      update_thread_list ();
 	    }
@@ -4964,6 +4975,9 @@ stop_all_threads (const char *reason)
 	     to tell the target to stop.  */
 	  for (thread_info *t : all_non_exited_threads ())
 	    {
+	      if (inf != nullptr && t->inf != inf)
+		continue;
+
 	      /* 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
@@ -5706,17 +5720,26 @@ handle_inferior_event (struct execution_control_state *ecs)
 }
 
 /* Restart threads back to what they were trying to do back when we
-   paused them for an in-line step-over.  The EVENT_THREAD thread is
-   ignored.  */
+   paused them (because of an in-line step-over or vfork, for example).
+   The EVENT_THREAD thread is ignored (not restarted).
+
+   If INF is non-nullptr, only resume threads from INF.  */
 
 static void
-restart_threads (struct thread_info *event_thread)
+restart_threads (struct thread_info *event_thread, inferior *inf)
 {
+  INFRUN_SCOPED_DEBUG_START_END ("event_thread=%s, inf=%d",
+				 event_thread->ptid.to_string ().c_str (),
+				 inf != nullptr ? inf->num : -1);
+
   /* In case the instruction just stepped spawned a new thread.  */
   update_thread_list ();
 
   for (thread_info *tp : all_non_exited_threads ())
     {
+      if (inf != nullptr && tp->inf != inf)
+	continue;
+
       if (tp->inf->detaching)
 	{
 	  infrun_debug_printf ("restart threads: [%s] inferior detaching",

gdb/infrun.h

@@ -141,8 +141,11 @@ extern void nullify_last_target_wait_ptid ();
 /* Stop all threads.  Only returns after everything is halted.
 
    REASON is a string indicating the reason why we stop all threads, used in
-   debug messages.  */
-extern void stop_all_threads (const char *reason);
+   debug messages.
+
+   If INF is non-nullptr, stop all threads of that inferior.  Otherwise, stop
+   all threads of all inferiors.  */
+extern void stop_all_threads (const char *reason, inferior *inf = nullptr);
 
 extern void prepare_for_detach (void);