commit b0117bb4cbe8d370e05be541eeade8d2adaf5138
author Todd Kjos <tkjos@google.com> Mon May 08 09:16:27 2017 -0700
committer Todd Kjos <tkjos@google.com> Thu Jul 13 08:34:20 2017 -0700
tree 89acfd8405fa62bbfeaf68806dcb9a081c5985bb
parent 2f993e208b128cfd32bc451ad37f226dd57ef766

FROMLIST: binder: refactor binder ref inc/dec for thread safety

(from https://patchwork.kernel.org/patch/9817781/)

Once locks are added, binder_ref's will only be accessed
safely with the proc lock held. Refactor the inc/dec paths
to make them atomic with the binder_get_ref* paths and
node inc/dec. For example, instead of:

  ref = binder_get_ref(proc, handle, strong);
  ...
  binder_dec_ref(ref, strong);

we now have:

  ret = binder_dec_ref_for_handle(proc, handle, strong, &rdata);

Since the actual ref is no longer exposed to callers, a
new struct binder_ref_data is introduced which can be used
to return a copy of ref state.

Change-Id: I11e6a31963eb18f5788cd52ae6ec9adb4438fa48
Signed-off-by: Todd Kjos <tkjos@google.com>

drivers/android/binder_trace.h

diff --git a/drivers/android/binder_trace.h b/drivers/android/binder_trace.h
index 50b0d21..7967db1 100644
--- a/drivers/android/binder_trace.h
+++ b/drivers/android/binder_trace.h
@@ -24,7 +24,7 @@
 struct binder_node;
 struct binder_proc;
 struct binder_alloc;
-struct binder_ref;
+struct binder_ref_data;
 struct binder_thread;
 struct binder_transaction;
 
@@ -147,8 +147,8 @@
 
 TRACE_EVENT(binder_transaction_node_to_ref,
 	TP_PROTO(struct binder_transaction *t, struct binder_node *node,
-		 struct binder_ref *ref),
-	TP_ARGS(t, node, ref),
+		 struct binder_ref_data *rdata),
+	TP_ARGS(t, node, rdata),
 
 	TP_STRUCT__entry(
 		__field(int, debug_id)
@@ -161,8 +161,8 @@
 		__entry->debug_id = t->debug_id;
 		__entry->node_debug_id = node->debug_id;
 		__entry->node_ptr = node->ptr;
-		__entry->ref_debug_id = ref->debug_id;
-		__entry->ref_desc = ref->desc;
+		__entry->ref_debug_id = rdata->debug_id;
+		__entry->ref_desc = rdata->desc;
 	),
 	TP_printk("transaction=%d node=%d src_ptr=0x%016llx ==> dest_ref=%d dest_desc=%d",
 		  __entry->debug_id, __entry->node_debug_id,
@@ -171,8 +171,9 @@
 );
 
 TRACE_EVENT(binder_transaction_ref_to_node,
-	TP_PROTO(struct binder_transaction *t, struct binder_ref *ref),
-	TP_ARGS(t, ref),
+	TP_PROTO(struct binder_transaction *t, struct binder_node *node,
+		 struct binder_ref_data *rdata),
+	TP_ARGS(t, node, rdata),
 
 	TP_STRUCT__entry(
 		__field(int, debug_id)
@@ -183,10 +184,10 @@
 	),
 	TP_fast_assign(
 		__entry->debug_id = t->debug_id;
-		__entry->ref_debug_id = ref->debug_id;
-		__entry->ref_desc = ref->desc;
-		__entry->node_debug_id = ref->node->debug_id;
-		__entry->node_ptr = ref->node->ptr;
+		__entry->ref_debug_id = rdata->debug_id;
+		__entry->ref_desc = rdata->desc;
+		__entry->node_debug_id = node->debug_id;
+		__entry->node_ptr = node->ptr;
 	),
 	TP_printk("transaction=%d node=%d src_ref=%d src_desc=%d ==> dest_ptr=0x%016llx",
 		  __entry->debug_id, __entry->node_debug_id,
@@ -195,9 +196,10 @@
 );
 
 TRACE_EVENT(binder_transaction_ref_to_ref,
-	TP_PROTO(struct binder_transaction *t, struct binder_ref *src_ref,
-		 struct binder_ref *dest_ref),
-	TP_ARGS(t, src_ref, dest_ref),
+	TP_PROTO(struct binder_transaction *t, struct binder_node *node,
+		 struct binder_ref_data *src_ref,
+		 struct binder_ref_data *dest_ref),
+	TP_ARGS(t, node, src_ref, dest_ref),
 
 	TP_STRUCT__entry(
 		__field(int, debug_id)
@@ -209,7 +211,7 @@
 	),
 	TP_fast_assign(
 		__entry->debug_id = t->debug_id;
-		__entry->node_debug_id = src_ref->node->debug_id;
+		__entry->node_debug_id = node->debug_id;
 		__entry->src_ref_debug_id = src_ref->debug_id;
 		__entry->src_ref_desc = src_ref->desc;
 		__entry->dest_ref_debug_id = dest_ref->debug_id;