grep: move sha1-reading mutex into low-level code

The multi-threaded git-grep code needs to serialize access
to the thread-unsafe read_sha1_file call. It does this with
a mutex that is local to builtin/grep.c.

Let's instead push this down into grep.c, where it can be
used by both builtin/grep.c and grep.c. This will let us
safely teach the low-level grep.c code tricks that involve
reading from the object db.

Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

1 files changed, 17 insertions, 0 deletions

diff --git a/grep.h b/grep.h
index 3653bb333c..4f1b0251b0 100644
--- a/grep.h
+++ b/grep.h
@@ -139,6 +139,23 @@ extern int grep_threads_ok(const struct grep_opt *opt);
  */
 extern int grep_use_locks;
 extern pthread_mutex_t grep_attr_mutex;
+extern pthread_mutex_t grep_read_mutex;
+
+static inline void grep_read_lock(void)
+{
+	if (grep_use_locks)
+		pthread_mutex_lock(&grep_read_mutex);
+}
+
+static inline void grep_read_unlock(void)
+{
+	if (grep_use_locks)
+		pthread_mutex_unlock(&grep_read_mutex);
+}
+
+#else
+#define grep_read_lock()
+#define grep_read_unlock()
 #endif
 
 #endif