object-store: allow threaded access to object reading

[thirdparty/git.git] / object-store.h

diff --git a/object-store.h b/object-store.h
index 33739c9deeb5f18ae878c75b88e7e452f30e38a9..7c80e0d64cbadf6f4db28d21b2c99aae0e952a9e 100644 (file)
--- a/object-store.h
+++ b/object-store.h
@@ -6,6 +6,7 @@
 #include "list.h"
 #include "sha1-array.h"
 #include "strbuf.h"
+#include "thread-utils.h"
 
 struct object_directory {
        struct object_directory *next;
@@ -251,6 +252,40 @@ int has_loose_object_nonlocal(const struct object_id *);
 
 void assert_oid_type(const struct object_id *oid, enum object_type expect);
 
+/*
+ * Enabling the object read lock allows multiple threads to safely call the
+ * following functions in parallel: repo_read_object_file(), read_object_file(),
+ * read_object_file_extended(), read_object_with_reference(), read_object(),
+ * oid_object_info() and oid_object_info_extended().
+ *
+ * obj_read_lock() and obj_read_unlock() may also be used to protect other
+ * section which cannot execute in parallel with object reading. Since the used
+ * lock is a recursive mutex, these sections can even contain calls to object
+ * reading functions. However, beware that in these cases zlib inflation won't
+ * be performed in parallel, losing performance.
+ *
+ * TODO: oid_object_info_extended()'s call stack has a recursive behavior. If
+ * any of its callees end up calling it, this recursive call won't benefit from
+ * parallel inflation.
+ */
+void enable_obj_read_lock(void);
+void disable_obj_read_lock(void);
+
+extern int obj_read_use_lock;
+extern pthread_mutex_t obj_read_mutex;
+
+static inline void obj_read_lock(void)
+{
+       if(obj_read_use_lock)
+               pthread_mutex_lock(&obj_read_mutex);
+}
+
+static inline void obj_read_unlock(void)
+{
+       if(obj_read_use_lock)
+               pthread_mutex_unlock(&obj_read_mutex);
+}
+
 struct object_info {
        /* Request */
        enum object_type *typep;