lib: Move lib/poll-loop.h to include/openvswitch

Poll-loop is the core to implement main loop. It should be available in
libopenvswitch.

Signed-off-by: Xiao Liang <shaw.leon@gmail.com>
Signed-off-by: Ben Pfaff <blp@ovn.org>

include/openvswitch/poll-loop.h

@@ -0,0 +1,83 @@
+/*
+ * Copyright (c) 2008, 2009, 2010, 2011, 2013, 2017 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.
+ */
+
+/* High-level wrapper around the "poll" system call.
+ *
+ * The intended usage is for each thread's main loop to go about its business
+ * servicing whatever events it needs to.  Then, when it runs out of immediate
+ * tasks, it calls each subordinate module's "wait" function, which in turn
+ * calls one (or more) of the functions poll_fd_wait(), poll_immediate_wake(),
+ * and poll_timer_wait() to register to be awakened when the appropriate event
+ * occurs.  Then the main loop calls poll_block(), which blocks until one of
+ * the registered events happens.
+ *
+ *
+ * Thread-safety
+ * =============
+ *
+ * The poll set is per-thread, so all functions in this module are thread-safe.
+ */
+#ifndef POLL_LOOP_H
+#define POLL_LOOP_H 1
+
+#ifndef _WIN32
+#include <poll.h>
+#endif
+
+#ifdef _WIN32
+#include <windows.h>
+#endif
+
+#ifdef  __cplusplus
+extern "C" {
+#endif
+
+
+/* Schedule events to wake up the following poll_block().
+ *
+ * The poll_loop logs the 'where' argument to each function at "debug" level
+ * when an event causes a wakeup.  Each of these ways to schedule an event has
+ * a function and a macro wrapper.  The macro version automatically supplies
+ * the source code location of the caller.  The function version allows the
+ * caller to supply a location explicitly, which is useful if the caller's own
+ * caller would be more useful in log output.  See timer_wait_at() for an
+ * example. */
+void poll_fd_wait_at(int fd, short int events, const char *where);
+#define poll_fd_wait(fd, events) poll_fd_wait_at(fd, events, OVS_SOURCE_LOCATOR)
+
+#ifdef _WIN32
+void poll_wevent_wait_at(HANDLE wevent, const char *where);
+#define poll_wevent_wait(wevent) poll_wevent_wait_at(wevent, OVS_SOURCE_LOCATOR)
+#endif /* _WIN32 */
+
+void poll_timer_wait_at(long long int msec, const char *where);
+#define poll_timer_wait(msec) poll_timer_wait_at(msec, OVS_SOURCE_LOCATOR)
+
+void poll_timer_wait_until_at(long long int msec, const char *where);
+#define poll_timer_wait_until(msec)             \
+    poll_timer_wait_until_at(msec, OVS_SOURCE_LOCATOR)
+
+void poll_immediate_wake_at(const char *where);
+#define poll_immediate_wake() poll_immediate_wake_at(OVS_SOURCE_LOCATOR)
+
+/* Wait until an event occurs. */
+void poll_block(void);
+
+#ifdef  __cplusplus
+}
+#endif
+
+#endif /* poll-loop.h */