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diff --git a/lib/poll-loop.h b/lib/poll-loop.h
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+++ b/lib/poll-loop.h
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+/*
+ * Copyright (c) 2008 Nicira Networks.
+ *
+ * Permission to use, copy, modify, and/or distribute this software for any
+ * purpose with or without fee is hereby granted, provided that the above
+ * copyright notice and this permission notice appear in all copies.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+ * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
+ * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
+ * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+ * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
+ * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
+ * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+ */
+
+/* High-level wrapper around the "poll" system call.
+ *
+ * Intended usage is for the program'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.
+ *
+ * There is also some support for autonomous subroutines that are executed by
+ * poll_block() when a file descriptor becomes ready.  To prevent these
+ * routines from starving if events are continuously ready, the application
+ * should bound the amount of work it does between poll_block() calls. */
+
+#ifndef POLL_LOOP_H
+#define POLL_LOOP_H 1
+
+#include <poll.h>
+
+struct poll_waiter;
+
+/* Schedule events to wake up the following poll_block(). */
+struct poll_waiter *poll_fd_wait(int fd, short int events);
+void poll_timer_wait(int msec);
+void poll_immediate_wake(void);
+
+/* Wait until an event occurs. */
+void poll_block(void);
+
+/* Autonomous function callbacks. */
+typedef void poll_fd_func(int fd, short int revents, void *aux);
+struct poll_waiter *poll_fd_callback(int fd, short int events,
+                                     poll_fd_func *, void *aux);
+
+/* Cancel a file descriptor callback or event. */
+void poll_cancel(struct poll_waiter *);
+
+#endif /* poll-loop.h */