Subject: [PATCH 3/5] Make lookup_*() functions thread-safe

From: Nguyễn Thái Ngọc Duy <[email-masked]>
Date: Tue, 10 Apr 2012 21:39:29 +0700

Signed-off-by: Nguyễn Thái Ngọc Duy <[email-masked]>
---
 blob.c         |   11 +++++++++--
 commit.c       |   12 +++++++++---
 list-objects.c |    2 ++
 object.c       |    9 ++++++++-
 object.h       |    6 ++++++
 tag.c          |    9 +++++++--
 tree.c         |   18 ++++++++++++++----
 7 files changed, 55 insertions(+), 12 deletions(-)

diff --git a/blob.c b/blob.c
index ae320bd..606e2be 100644
--- a/blob.c
+++ b/blob.c
@@ -6,8 +6,13 @@ const char *blob_type = "blob";
 struct blob *lookup_blob(const unsigned char *sha1)
 {
 	struct object *obj = lookup_object(sha1);
-	if (!obj)
-		return create_object(sha1, OBJ_BLOB, alloc_blob_node());
+	LOCK();
+	if (!obj) {
+		obj = create_object(sha1, OBJ_BLOB, alloc_blob_node());
+		UNLOCK();
+		return obj;
+	}
+	UNLOCK();
 	if (!obj->type)
 		obj->type = OBJ_BLOB;
 	if (obj->type != OBJ_BLOB) {
@@ -20,6 +25,8 @@ struct blob *lookup_blob(const unsigned char *sha1)
 
 int parse_blob_buffer(struct blob *item, void *buffer, unsigned long size)
 {
+	LOCK();
 	item->object.parsed = 1;
+	UNLOCK();
 	return 0;
 }
diff --git a/commit.c b/commit.c
index 4b39c19..f84152c 100644
--- a/commit.c
+++ b/commit.c
@@ -54,9 +54,15 @@ struct commit *lookup_commit_or_die(const unsigned char *sha1, const char *ref_n
 
 struct commit *lookup_commit(const unsigned char *sha1)
 {
-	struct object *obj = lookup_object(sha1);
-	if (!obj)
-		return create_object(sha1, OBJ_COMMIT, alloc_commit_node());
+	struct object *obj;
+	LOCK();
+	obj = lookup_object(sha1);
+	if (!obj) {
+		obj = create_object(sha1, OBJ_COMMIT, alloc_commit_node());
+		UNLOCK();
+		return (struct commit*)obj;
+	}
+	UNLOCK();
 	if (!obj->type)
 		obj->type = OBJ_COMMIT;
 	return check_commit(obj, sha1, 0);
diff --git a/list-objects.c b/list-objects.c
index 3dd4a96..2605b63 100644
--- a/list-objects.c
+++ b/list-objects.c
@@ -123,8 +123,10 @@ static void process_tree(struct rev_info *revs,
 				     cb_data);
 	}
 	strbuf_setlen(base, baselen);
+	LOCK();
 	free(tree->buffer);
 	tree->buffer = NULL;
+	UNLOCK();
 }
 
 static void mark_edge_parents_uninteresting(struct commit *commit,
diff --git a/object.c b/object.c
index 6b06297..05fb91f 100644
--- a/object.c
+++ b/object.c
@@ -8,6 +8,9 @@
 static struct object **obj_hash;
 static int nr_objs, obj_hash_size;
 
+int multithread_object_access;
+pthread_mutex_t mtx;
+
 unsigned int get_max_object_index(void)
 {
 	return obj_hash_size;
@@ -126,9 +129,13 @@ void *create_object(const unsigned char *sha1, int type, void *o)
 
 struct object *lookup_unknown_object(const unsigned char *sha1)
 {
-	struct object *obj = lookup_object(sha1);
+	struct object *obj;
+
+	LOCK();
+	obj = lookup_object(sha1);
 	if (!obj)
 		obj = create_object(sha1, OBJ_NONE, alloc_object_node());
+	UNLOCK();
 	return obj;
 }
 
diff --git a/object.h b/object.h
index b6618d9..17c7c65 100644
--- a/object.h
+++ b/object.h
@@ -32,6 +32,12 @@ struct object {
 	unsigned char sha1[20];
 };
 
+extern int multithread_object_access;
+extern pthread_mutex_t mtx;
+
+#define LOCK() { if (multithread_object_access) pthread_mutex_lock(&mtx); }
+#define UNLOCK() { if (multithread_object_access) pthread_mutex_unlock(&mtx); }
+
 extern const char *typename(unsigned int type);
 extern int type_from_string(const char *str);
 
diff --git a/tag.c b/tag.c
index 78d272b..4f16c5b 100644
--- a/tag.c
+++ b/tag.c
@@ -39,8 +39,13 @@ struct object *deref_tag_noverify(struct object *o)
 struct tag *lookup_tag(const unsigned char *sha1)
 {
 	struct object *obj = lookup_object(sha1);
-	if (!obj)
-		return create_object(sha1, OBJ_TAG, alloc_tag_node());
+	LOCK();
+	if (!obj) {
+		obj = create_object(sha1, OBJ_TAG, alloc_tag_node());
+		UNLOCK();
+		return obj;
+	}
+	UNLOCK();
 	if (!obj->type)
 		obj->type = OBJ_TAG;
 	if (obj->type != OBJ_TAG) {
diff --git a/tree.c b/tree.c
index 676e9f7..6d3c6a2 100644
--- a/tree.c
+++ b/tree.c
@@ -180,9 +180,15 @@ int read_tree(struct tree *tree, int stage, struct pathspec *match)
 
 struct tree *lookup_tree(const unsigned char *sha1)
 {
-	struct object *obj = lookup_object(sha1);
-	if (!obj)
-		return create_object(sha1, OBJ_TREE, alloc_tree_node());
+	struct object *obj;
+	LOCK();
+	obj = lookup_object(sha1);
+	if (!obj) {
+		obj = create_object(sha1, OBJ_TREE, alloc_tree_node());
+		UNLOCK();
+		return obj;
+	}
+	UNLOCK();
 	if (!obj->type)
 		obj->type = OBJ_TREE;
 	if (obj->type != OBJ_TREE) {
@@ -195,11 +201,15 @@ struct tree *lookup_tree(const unsigned char *sha1)
 
 int parse_tree_buffer(struct tree *item, void *buffer, unsigned long size)
 {
-	if (item->object.parsed)
+	LOCK();
+	if (item->object.parsed) {
+		UNLOCK();
 		return 0;
+	}
 	item->object.parsed = 1;
 	item->buffer = buffer;
 	item->size = size;
+	UNLOCK();
 
 	return 0;
 }
-- 
1.7.8.36.g69ee2