openflow build environment setup

openflow/include/openvswitch/thread.h

@@ -0,0 +1,137 @@
+/*
+ * Copyright (c) 2013, 2014 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 OPENVSWITCH_THREAD_H
+#define OPENVSWITCH_THREAD_H 1
+
+#include <pthread.h>
+#include <stddef.h>
+#include <stdbool.h>
+#include <sys/types.h>
+#include "openvswitch/compiler.h"
+
+/* Mutex. */
+struct OVS_LOCKABLE ovs_mutex {
+    pthread_mutex_t lock;
+    const char *where;          /* NULL if and only if uninitialized. */
+};
+
+/* "struct ovs_mutex" initializer. */
+#ifdef PTHREAD_ERRORCHECK_MUTEX_INITIALIZER_NP
+#define OVS_MUTEX_INITIALIZER { PTHREAD_ERRORCHECK_MUTEX_INITIALIZER_NP, \
+                                "<unlocked>" }
+#else
+#define OVS_MUTEX_INITIALIZER { PTHREAD_MUTEX_INITIALIZER, "<unlocked>" }
+#endif
+
+#ifdef PTHREAD_ADAPTIVE_MUTEX_INITIALIZER_NP
+#define OVS_ADAPTIVE_MUTEX_INITIALIZER                  \
+    { PTHREAD_ADAPTIVE_MUTEX_INITIALIZER_NP, "<unlocked>" }
+#else
+#define OVS_ADAPTIVE_MUTEX_INITIALIZER OVS_MUTEX_INITIALIZER
+#endif
+
+/* ovs_mutex functions analogous to pthread_mutex_*() functions.
+ *
+ * Most of these functions abort the process with an error message on any
+ * error.  ovs_mutex_trylock() is an exception: it passes through a 0 or EBUSY
+ * return value to the caller and aborts on any other error. */
+void ovs_mutex_init(const struct ovs_mutex *);
+void ovs_mutex_init_recursive(const struct ovs_mutex *);
+void ovs_mutex_init_adaptive(const struct ovs_mutex *);
+void ovs_mutex_destroy(const struct ovs_mutex *);
+void ovs_mutex_unlock(const struct ovs_mutex *mutex) OVS_RELEASES(mutex);
+void ovs_mutex_lock_at(const struct ovs_mutex *mutex, const char *where)
+    OVS_ACQUIRES(mutex);
+#define ovs_mutex_lock(mutex) \
+        ovs_mutex_lock_at(mutex, OVS_SOURCE_LOCATOR)
+
+int ovs_mutex_trylock_at(const struct ovs_mutex *mutex, const char *where)
+    OVS_TRY_LOCK(0, mutex);
+#define ovs_mutex_trylock(mutex) \
+        ovs_mutex_trylock_at(mutex, OVS_SOURCE_LOCATOR)
+
+void ovs_mutex_cond_wait(pthread_cond_t *, const struct ovs_mutex *);
+
+/* Convenient once-only execution.
+ *
+ *
+ * Problem
+ * =======
+ *
+ * POSIX provides pthread_once_t and pthread_once() as primitives for running a
+ * set of code only once per process execution.  They are used like this:
+ *
+ *     static void run_once(void) { ...initialization... }
+ *     static pthread_once_t once = PTHREAD_ONCE_INIT;
+ * ...
+ *     pthread_once(&once, run_once);
+ *
+ * pthread_once() does not allow passing any parameters to the initialization
+ * function, which is often inconvenient, because it means that the function
+ * can only access data declared at file scope.
+ *
+ *
+ * Solution
+ * ========
+ *
+ * Use ovsthread_once, like this, instead:
+ *
+ *     static struct ovsthread_once once = OVSTHREAD_ONCE_INITIALIZER;
+ *
+ *     if (ovsthread_once_start(&once)) {
+ *         ...initialization...
+ *         ovsthread_once_done(&once);
+ *     }
+ */
+
+struct ovsthread_once {
+    bool done;               /* Non-atomic, false negatives possible. */
+    struct ovs_mutex mutex;
+};
+
+#define OVSTHREAD_ONCE_INITIALIZER              \
+    {                                           \
+        false,                                  \
+        OVS_MUTEX_INITIALIZER,                  \
+    }
+
+static inline bool ovsthread_once_start(struct ovsthread_once *once)
+    OVS_TRY_LOCK(true, once->mutex);
+void ovsthread_once_done(struct ovsthread_once *once)
+    OVS_RELEASES(once->mutex);
+
+bool ovsthread_once_start__(struct ovsthread_once *once)
+    OVS_TRY_LOCK(true, once->mutex);
+
+/* Returns true if this is the first call to ovsthread_once_start() for
+ * 'once'.  In this case, the caller should perform whatever initialization
+ * actions it needs to do, then call ovsthread_once_done() for 'once'.
+ *
+ * Returns false if this is not the first call to ovsthread_once_start() for
+ * 'once'.  In this case, the call will not return until after
+ * ovsthread_once_done() has been called. */
+static inline bool
+ovsthread_once_start(struct ovsthread_once *once)
+{
+    /* We may be reading 'done' at the same time as the first thread
+     * is writing on it, or we can be using a stale copy of it.  The
+     * worst that can happen is that we call ovsthread_once_start__()
+     * once when strictly not necessary. */
+    return OVS_UNLIKELY(!once->done && ovsthread_once_start__(once));
+}
+
+#endif /* ovs-thread.h */