shared: add generic IPC barrier

[elogind.git] / src / shared / barrier.h

diff --git a/src/shared/barrier.h b/src/shared/barrier.h
new file mode 100644 (file)
index 0000000..7f76ec7
--- /dev/null
+++ b/src/shared/barrier.h
@@ -0,0 +1,92 @@
+/*-*- Mode: C; c-basic-offset: 8; indent-tabs-mode: nil -*-*/
+
+#pragma once
+
+/***
+  This file is part of systemd.
+
+  Copyright 2014 David Herrmann <dh.herrmann@gmail.com>
+
+  systemd is free software; you can redistribute it and/or modify it
+  under the terms of the GNU Lesser General Public License as published by
+  the Free Software Foundation; either version 2.1 of the License, or
+  (at your option) any later version.
+
+  systemd is distributed in the hope that it will be useful, but
+  WITHOUT ANY WARRANTY; without even the implied warranty of
+  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+  Lesser General Public License for more details.
+
+  You should have received a copy of the GNU Lesser General Public License
+  along with systemd; If not, see <http://www.gnu.org/licenses/>.
+***/
+
+#include <errno.h>
+#include <inttypes.h>
+#include <stdlib.h>
+#include <string.h>
+#include <sys/types.h>
+
+#include "macro.h"
+#include "util.h"
+
+/* See source file for an API description. */
+
+typedef struct Barrier Barrier;
+
+enum {
+        BARRIER_SINGLE                  = 1LL,
+        BARRIER_ABORTION                = INT64_MAX,
+
+        /* bias values to store state; keep @WE < @THEY < @I */
+        BARRIER_BIAS                    = INT64_MIN,
+        BARRIER_WE_ABORTED              = BARRIER_BIAS + 1LL,
+        BARRIER_THEY_ABORTED            = BARRIER_BIAS + 2LL,
+        BARRIER_I_ABORTED               = BARRIER_BIAS + 3LL,
+};
+
+enum {
+        BARRIER_PARENT,
+        BARRIER_CHILD,
+};
+
+struct Barrier {
+        int me;
+        int them;
+        int pipe[2];
+        int64_t barriers;
+};
+
+int barrier_init(Barrier *obj);
+void barrier_destroy(Barrier *b);
+
+void barrier_set_role(Barrier *b, unsigned int role);
+
+bool barrier_place(Barrier *b);
+bool barrier_abort(Barrier *b);
+
+bool barrier_wait_next(Barrier *b);
+bool barrier_wait_abortion(Barrier *b);
+bool barrier_sync_next(Barrier *b);
+bool barrier_sync(Barrier *b);
+
+static inline bool barrier_i_aborted(Barrier *b) {
+        return b->barriers == BARRIER_I_ABORTED || b->barriers == BARRIER_WE_ABORTED;
+}
+
+static inline bool barrier_they_aborted(Barrier *b) {
+        return b->barriers == BARRIER_THEY_ABORTED || b->barriers == BARRIER_WE_ABORTED;
+}
+
+static inline bool barrier_we_aborted(Barrier *b) {
+        return b->barriers == BARRIER_WE_ABORTED;
+}
+
+static inline bool barrier_is_aborted(Barrier *b) {
+        return b->barriers == BARRIER_I_ABORTED || b->barriers == BARRIER_THEY_ABORTED || b->barriers == BARRIER_WE_ABORTED;
+}
+
+static inline bool barrier_place_and_sync(Barrier *b) {
+        barrier_place(b);
+        return barrier_sync(b);
+}