latch: New module for a thread-safe, signal-safe, pollable doorbell.

[sliver-openvswitch.git] / lib / latch.h

diff --git a/lib/latch.h b/lib/latch.h
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+/*
+ * Copyright (c) 2013 Nicira, Inc.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at:
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#ifndef LATCH_H
+#define LATCH_H 1
+
+/* A thread-safe, signal-safe, pollable doorbell.
+ *
+ * This is a thin wrapper around a pipe that allows threads to notify each
+ * other that an event has occurred in a signal-safe way  */
+
+#include <stdbool.h>
+#include "util.h"
+
+struct latch {
+    int fds[2];
+};
+
+void latch_init(struct latch *);
+void latch_destroy(struct latch *);
+
+bool latch_poll(struct latch *);
+void latch_set(struct latch *);
+
+bool latch_is_set(const struct latch *);
+void latch_wait(const struct latch *, const char *where);
+#define latch_wait(latch) latch_wait(latch, SOURCE_LOCATOR)
+
+#endif /* latch.h */