binder: refactor binder_pop_transaction

binder_pop_transaction needs to be split into 2 pieces to
to allow the proc lock to be held on entry to dequeue the
transaction stack, but no lock when kfree'ing the transaction.

Split into binder_pop_transaction_locked and binder_free_transaction
(the actual locks are still to be added).

Signed-off-by: Todd Kjos <tkjos@google.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/android/binder.c

@@ -768,14 +768,16 @@ static int binder_dec_ref(struct binder_ref *ref, int strong)
 static void binder_pop_transaction(struct binder_thread *target_thread,
 				   struct binder_transaction *t)
 {
-	if (target_thread) {
-		BUG_ON(target_thread->transaction_stack != t);
-		BUG_ON(target_thread->transaction_stack->from != target_thread);
-		target_thread->transaction_stack =
-			target_thread->transaction_stack->from_parent;
-		t->from = NULL;
-	}
-	t->need_reply = 0;
+	BUG_ON(!target_thread);
+	BUG_ON(target_thread->transaction_stack != t);
+	BUG_ON(target_thread->transaction_stack->from != target_thread);
+	target_thread->transaction_stack =
+		target_thread->transaction_stack->from_parent;
+	t->from = NULL;
+}
+
+static void binder_free_transaction(struct binder_transaction *t)
+{
 	if (t->buffer)
 		t->buffer->transaction = NULL;
 	kfree(t);
@@ -808,6 +810,7 @@ static void binder_send_failed_reply(struct binder_transaction *t,
 				binder_pop_transaction(target_thread, t);
 				target_thread->return_error = error_code;
 				wake_up_interruptible(&target_thread->wait);
+				binder_free_transaction(t);
 			} else {
 				pr_err("reply failed, target thread, %d:%d, has error code %d already\n",
 					target_thread->proc->pid,
@@ -822,7 +825,7 @@ static void binder_send_failed_reply(struct binder_transaction *t,
 			     "send failed reply for transaction %d, target dead\n",
 			     t->debug_id);
 
-		binder_pop_transaction(target_thread, t);
+		binder_free_transaction(t);
 		if (next == NULL) {
 			binder_debug(BINDER_DEBUG_DEAD_BINDER,
 				     "reply failed, no target thread at root\n");
@@ -1806,6 +1809,7 @@ static void binder_transaction(struct binder_proc *proc,
 	if (reply) {
 		BUG_ON(t->buffer->async_transaction != 0);
 		binder_pop_transaction(target_thread, in_reply_to);
+		binder_free_transaction(in_reply_to);
 	} else if (!(t->flags & TF_ONE_WAY)) {
 		BUG_ON(t->buffer->async_transaction != 0);
 		t->need_reply = 1;
@@ -2635,9 +2639,7 @@ retry:
 			t->to_thread = thread;
 			thread->transaction_stack = t;
 		} else {
-			t->buffer->transaction = NULL;
-			kfree(t);
-			binder_stats_deleted(BINDER_STAT_TRANSACTION);
+			binder_free_transaction(t);
 		}
 		break;
 	}
@@ -2680,9 +2682,7 @@ static void binder_release_work(struct list_head *list)
 				binder_debug(BINDER_DEBUG_DEAD_TRANSACTION,
 					"undelivered transaction %d\n",
 					t->debug_id);
-				t->buffer->transaction = NULL;
-				kfree(t);
-				binder_stats_deleted(BINDER_STAT_TRANSACTION);
+				binder_free_transaction(t);
 			}
 		} break;
 		case BINDER_WORK_TRANSACTION_COMPLETE: {