index: get rid of the locking

We don't support using an index object from multiple threads at the same
time, so the locking doesn't have any effect when following the
rules. If not following the rules, things are going to break down
anyway.

src/index.c

@@ -356,28 +356,6 @@ static unsigned int index_merge_mode(
 	return git_index__create_mode(mode);
 }
 
-static int index_sort_if_needed(git_index *index, bool need_lock)
-{
-	/* not truly threadsafe because between when this checks and/or
-	 * sorts the array another thread could come in and unsort it
-	 */
-
-	if (git_vector_is_sorted(&index->entries))
-		return 0;
-
-	if (need_lock && git_mutex_lock(&index->lock) < 0) {
-		giterr_set(GITERR_OS, "Unable to lock index");
-		return -1;
-	}
-
-	git_vector_sort(&index->entries);
-
-	if (need_lock)
-		git_mutex_unlock(&index->lock);
-
-	return 0;
-}
-
 GIT_INLINE(int) index_find_in_entries(
 	size_t *out, git_vector *entries, git_vector_cmp entry_srch,
 	const char *path, size_t path_len, int stage)
@@ -391,10 +369,9 @@ GIT_INLINE(int) index_find_in_entries(
 
 GIT_INLINE(int) index_find(
 	size_t *out, git_index *index,
-	const char *path, size_t path_len, int stage, bool need_lock)
+	const char *path, size_t path_len, int stage)
 {
-	if (index_sort_if_needed(index, need_lock) < 0)
-		return -1;
+	git_vector_sort(&index->entries);
 
 	return index_find_in_entries(
 		out, &index->entries, index->entries_search, path, path_len, stage);
@@ -418,7 +395,7 @@ void git_index__set_ignore_case(git_index *index, bool ignore_case)
 
 	git_vector_set_cmp(&index->entries,
 		ignore_case ? git_index_entry_icmp : git_index_entry_cmp);
-	index_sort_if_needed(index, true);
+	git_vector_sort(&index->entries);
 
 	git_vector_set_cmp(&index->reuc, ignore_case ? reuc_icmp : reuc_cmp);
 	git_vector_sort(&index->reuc);
@@ -434,12 +411,6 @@ int git_index_open(git_index **index_out, const char *index_path)
 	index = git__calloc(1, sizeof(git_index));
 	GITERR_CHECK_ALLOC(index);
 
-	if (git_mutex_init(&index->lock)) {
-		giterr_set(GITERR_OS, "Failed to initialize lock");
-		git__free(index);
-		return -1;
-	}
-
 	git_pool_init(&index->tree_pool, 1);
 
 	if (index_path != NULL) {
@@ -498,7 +469,6 @@ static void index_free(git_index *index)
 	git_vector_free(&index->deleted);
 
 	git__free(index->index_file_path);
-	git_mutex_free(&index->lock);
 
 	git__memzero(index, sizeof(*index));
 	git__free(index);
@@ -561,11 +531,6 @@ int git_index_clear(git_index *index)
 	index->tree = NULL;
 	git_pool_clear(&index->tree_pool);
 
-	if (git_mutex_lock(&index->lock) < 0) {
-		giterr_set(GITERR_OS, "Failed to lock index");
-		return -1;
-	}
-
 	git_idxmap_clear(index->entries_map);
 	while (!error && index->entries.length > 0)
 		error = index_remove_entry(index, index->entries.length - 1);
@@ -576,8 +541,6 @@ int git_index_clear(git_index *index)
 
 	git_futils_filestamp_set(&index->stamp, NULL);
 
-	git_mutex_unlock(&index->lock);
-
 	return error;
 }
 
@@ -836,8 +799,7 @@ const git_index_entry *git_index_get_byindex(
 	git_index *index, size_t n)
 {
 	assert(index);
-	if (index_sort_if_needed(index, true) < 0)
-		return NULL;
+	git_vector_sort(&index->entries);
 	return git_vector_get(&index->entries, n);
 }
 
@@ -1094,7 +1056,7 @@ static int has_dir_name(git_index *index,
 		}
 		len = slash - name;
 
-		if (!index_find(&pos, index, name, len, stage, false)) {
+		if (!index_find(&pos, index, name, len, stage)) {
 			retval = -1;
 			if (!ok_to_replace)
 				break;
@@ -1231,7 +1193,7 @@ static void index_existing_and_best(
 	int error;
 
 	error = index_find(&pos,
-		index, entry->path, 0, GIT_IDXENTRY_STAGE(entry), false);
+		index, entry->path, 0, GIT_IDXENTRY_STAGE(entry));
 
 	if (error == 0) {
 		*existing = index->entries.contents[pos];
@@ -1296,11 +1258,6 @@ static int index_insert(
 	/* this entry is now up-to-date and should not be checked for raciness */
 	entry->flags_extended |= GIT_IDXENTRY_UPTODATE;
 
-	if (git_mutex_lock(&index->lock) < 0) {
-		giterr_set(GITERR_OS, "Unable to acquire index lock");
-		return -1;
-	}
-
 	git_vector_sort(&index->entries);
 
 	/* look if an entry with this path already exists, either staged, or (if
@@ -1355,8 +1312,6 @@ static int index_insert(
 		*entry_ptr = NULL;
 	}
 
-	git_mutex_unlock(&index->lock);
-
 	return error;
 }
 
@@ -1559,11 +1514,6 @@ int git_index__fill(git_index *index, const git_vector *source_entries)
 	if (!source_entries->length)
 		return 0;
 
-	if (git_mutex_lock(&index->lock) < 0) {
-		giterr_set(GITERR_OS, "Unable to acquire index lock");
-		return -1;
-	}
-
 	git_vector_size_hint(&index->entries, source_entries->length);
 	git_idxmap_resize(index->entries_map, source_entries->length * 1.3);
 
@@ -1588,7 +1538,6 @@ int git_index__fill(git_index *index, const git_vector *source_entries)
 	if (!ret)
 		git_vector_sort(&index->entries);
 
-	git_mutex_unlock(&index->lock);
 	return ret;
 }
 
@@ -1619,17 +1568,12 @@ int git_index_remove(git_index *index, const char *path, int stage)
 	size_t position;
 	git_index_entry remove_key = {{ 0 }};
 
-	if (git_mutex_lock(&index->lock) < 0) {
-		giterr_set(GITERR_OS, "Failed to lock index");
-		return -1;
-	}
-
 	remove_key.path = path;
 	GIT_IDXENTRY_STAGE_SET(&remove_key, stage);
 
 	DELETE_IN_MAP(index, &remove_key);
 
-	if (index_find(&position, index, path, 0, stage, false) < 0) {
+	if (index_find(&position, index, path, 0, stage) < 0) {
 		giterr_set(
 			GITERR_INDEX, "Index does not contain %s at stage %d", path, stage);
 		error = GIT_ENOTFOUND;
@@ -1637,7 +1581,6 @@ int git_index_remove(git_index *index, const char *path, int stage)
 		error = index_remove_entry(index, position);
 	}
 
-	git_mutex_unlock(&index->lock);
 	return error;
 }
 
@@ -1648,14 +1591,9 @@ int git_index_remove_directory(git_index *index, const char *dir, int stage)
 	size_t pos;
 	git_index_entry *entry;
 
-	if (git_mutex_lock(&index->lock) < 0) {
-		giterr_set(GITERR_OS, "Failed to lock index");
-		return -1;
-	}
-
 	if (!(error = git_buf_sets(&pfx, dir)) &&
 		!(error = git_path_to_dir(&pfx)))
-		index_find(&pos, index, pfx.ptr, pfx.size, GIT_INDEX_STAGE_ANY, false);
+		index_find(&pos, index, pfx.ptr, pfx.size, GIT_INDEX_STAGE_ANY);
 
 	while (!error) {
 		entry = git_vector_get(&index->entries, pos);
@@ -1672,7 +1610,6 @@ int git_index_remove_directory(git_index *index, const char *dir, int stage)
 		/* removed entry at 'pos' so we don't need to increment */
 	}
 
-	git_mutex_unlock(&index->lock);
 	git_buf_free(&pfx);
 
 	return error;
@@ -1684,12 +1621,7 @@ int git_index_find_prefix(size_t *at_pos, git_index *index, const char *prefix)
 	size_t pos;
 	const git_index_entry *entry;
 
-	if (git_mutex_lock(&index->lock) < 0) {
-		giterr_set(GITERR_OS, "Failed to lock index");
-		return -1;
-	}
-
-	index_find(&pos, index, prefix, strlen(prefix), GIT_INDEX_STAGE_ANY, false);
+	index_find(&pos, index, prefix, strlen(prefix), GIT_INDEX_STAGE_ANY);
 	entry = git_vector_get(&index->entries, pos);
 	if (!entry || git__prefixcmp(entry->path, prefix) != 0)
 		error = GIT_ENOTFOUND;
@@ -1697,8 +1629,6 @@ int git_index_find_prefix(size_t *at_pos, git_index *index, const char *prefix)
 	if (!error && at_pos)
 		*at_pos = pos;
 
-	git_mutex_unlock(&index->lock);
-
 	return error;
 }
 
@@ -1706,7 +1636,7 @@ int git_index__find_pos(
 	size_t *out, git_index *index, const char *path, size_t path_len, int stage)
 {
 	assert(index && path);
-	return index_find(out, index, path, path_len, stage, true);
+	return index_find(out, index, path, path_len, stage);
 }
 
 int git_index_find(size_t *at_pos, git_index *index, const char *path)
@@ -1715,14 +1645,8 @@ int git_index_find(size_t *at_pos, git_index *index, const char *path)
 
 	assert(index && path);
 
-	if (git_mutex_lock(&index->lock) < 0) {
-		giterr_set(GITERR_OS, "Failed to lock index");
-		return -1;
-	}
-
 	if (git_vector_bsearch2(
 			&pos, &index->entries, index->entries_search_path, path) < 0) {
-		git_mutex_unlock(&index->lock);
 		giterr_set(GITERR_INDEX, "Index does not contain %s", path);
 		return GIT_ENOTFOUND;
 	}
@@ -1740,7 +1664,6 @@ int git_index_find(size_t *at_pos, git_index *index, const char *path)
 	if (at_pos)
 		*at_pos = pos;
 
-	git_mutex_unlock(&index->lock);
 	return 0;
 }
 
@@ -1896,11 +1819,6 @@ static int index_conflict_remove(git_index *index, const char *path)
 	if (path != NULL && git_index_find(&pos, index, path) < 0)
 		return GIT_ENOTFOUND;
 
-	if (git_mutex_lock(&index->lock) < 0) {
-		giterr_set(GITERR_OS, "Unable to lock index");
-		return -1;
-	}
-
 	while ((conflict_entry = git_vector_get(&index->entries, pos)) != NULL) {
 
 		if (path != NULL &&
@@ -1916,8 +1834,6 @@ static int index_conflict_remove(git_index *index, const char *path)
 			break;
 	}
 
-	git_mutex_unlock(&index->lock);
-
 	return error;
 }
 
@@ -2456,11 +2372,6 @@ static int parse_index(git_index *index, const char *buffer, size_t buffer_size)
 
 	seek_forward(INDEX_HEADER_SIZE);
 
-	if (git_mutex_lock(&index->lock) < 0) {
-		giterr_set(GITERR_OS, "Unable to acquire index lock");
-		return -1;
-	}
-
 	assert(!index->entries.length);
 
 	if (index->ignore_case)
@@ -2490,6 +2401,7 @@ static int parse_index(git_index *index, const char *buffer, size_t buffer_size)
 			index_entry_free(entry);
 			goto done;
 		}
+		error = 0;
 
 		seek_forward(entry_size);
 	}
@@ -2537,10 +2449,9 @@ static int parse_index(git_index *index, const char *buffer, size_t buffer_size)
 	 * in-memory index is supposed to be case-insensitive
 	 */
 	git_vector_set_sorted(&index->entries, !index->ignore_case);
-	error = index_sort_if_needed(index, false);
+	git_vector_sort(&index->entries);
 
 done:
-	git_mutex_unlock(&index->lock);
 	return error;
 }
 
@@ -2630,11 +2541,6 @@ static int write_entries(git_index *index, git_filebuf *file)
 	git_vector case_sorted, *entries;
 	git_index_entry *entry;
 
-	if (git_mutex_lock(&index->lock) < 0) {
-		giterr_set(GITERR_OS, "Failed to lock index");
-		return -1;
-	}
-
 	/* If index->entries is sorted case-insensitively, then we need
 	 * to re-sort it case-sensitively before writing */
 	if (index->ignore_case) {
@@ -2649,8 +2555,6 @@ static int write_entries(git_index *index, git_filebuf *file)
 		if ((error = write_disk_entry(file, entry)) < 0)
 			break;
 
-	git_mutex_unlock(&index->lock);
-
 	if (index->ignore_case)
 		git_vector_free(&case_sorted);
 
@@ -2935,8 +2839,7 @@ int git_index_read_tree(git_index *index, const git_tree *tree)
 	index->tree = NULL;
 	git_pool_clear(&index->tree_pool);
 
-	if (index_sort_if_needed(index, true) < 0)
-		return -1;
+	git_vector_sort(&index->entries);
 
 	if ((error = git_tree_walk(tree, GIT_TREEWALK_POST, read_tree_cb, &data)) < 0)
 		goto cleanup;
@@ -2959,15 +2862,11 @@ int git_index_read_tree(git_index *index, const git_tree *tree)
 
 	git_vector_sort(&entries);
 
-	if ((error = git_index_clear(index)) < 0)
+	if ((error = git_index_clear(index)) < 0) {
 		/* well, this isn't good */;
-	else if (git_mutex_lock(&index->lock) < 0) {
-		giterr_set(GITERR_OS, "Unable to acquire index lock");
-		error = -1;
 	} else {
 		git_vector_swap(&entries, &index->entries);
 		entries_map = git__swap(index->entries_map, entries_map);
-		git_mutex_unlock(&index->lock);
 	}
 
 cleanup:
@@ -3367,18 +3266,11 @@ int git_index_snapshot_new(git_vector *snap, git_index *index)
 
 	GIT_REFCOUNT_INC(index);
 
-	if (git_mutex_lock(&index->lock) < 0) {
-		giterr_set(GITERR_OS, "Failed to lock index");
-		return -1;
-	}
-
 	git_atomic_inc(&index->readers);
 	git_vector_sort(&index->entries);
 
 	error = git_vector_dup(snap, &index->entries, index->entries._cmp);
 
-	git_mutex_unlock(&index->lock);
-
 	if (error < 0)
 		git_index_free(index);
 
@@ -3391,11 +3283,6 @@ void git_index_snapshot_release(git_vector *snap, git_index *index)
 
 	git_atomic_dec(&index->readers);
 
-	if (!git_mutex_lock(&index->lock)) {
-		index_free_deleted(index); /* try to free pending deleted items */
-		git_mutex_unlock(&index->lock);
-	}
-
 	git_index_free(index);
 }
 
@@ -3460,9 +3347,7 @@ int git_indexwriter_commit(git_indexwriter *writer)
 	if (!writer->should_write)
 		return 0;
 
-	if (index_sort_if_needed(writer->index, true) < 0)
-		return -1;
-
+	git_vector_sort(&writer->index->entries);
 	git_vector_sort(&writer->index->reuc);
 
 	if ((error = write_index(&checksum, writer->index, &writer->file)) < 0) {

src/index.h

@@ -28,7 +28,6 @@ struct git_index {
 	git_vector entries;
 	git_idxmap *entries_map;
 
-	git_mutex  lock;    /* lock held while entries is being changed */
 	git_vector deleted; /* deleted entries if readers > 0 */
 	git_atomic readers; /* number of active iterators */