selinux_restorecon: add a global mutex to synchronize progress output

Another small incremental change to pave the way for a parallel
selinux_restorecon() function.

Signed-off-by: Ondrej Mosnacek <omosnace@redhat.com>
diff --git a/libselinux/src/selinux_restorecon.c b/libselinux/src/selinux_restorecon.c
index 732f0cc..252b775 100644
--- a/libselinux/src/selinux_restorecon.c
+++ b/libselinux/src/selinux_restorecon.c
@@ -60,6 +60,7 @@
 static struct edir *exclude_lst = NULL;
 static uint64_t fc_count = 0;	/* Number of files processed so far */
 static uint64_t efile_count;	/* Estimated total number of files */
+static pthread_mutex_t progress_mutex = PTHREAD_MUTEX_INITIALIZER;
 
 /* Store information on directories with xattr's. */
 static struct dir_xattr *dir_xattr_list;
@@ -647,6 +648,7 @@
 	}
 
 	if (flags->progress) {
+		__pthread_mutex_lock(&progress_mutex);
 		fc_count++;
 		if (fc_count % STAR_COUNT == 0) {
 			if (flags->mass_relabel && efile_count > 0) {
@@ -658,6 +660,7 @@
 			}
 			fflush(stdout);
 		}
+		__pthread_mutex_unlock(&progress_mutex);
 	}
 
 	if (flags->add_assoc) {