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/*
* 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"
#ifdef __cplusplus
extern "C" {
#endif
/* Mutex. */
struct OVS_LOCKABLE ovs_mutex {
pthread_mutex_t lock;
const char *where; /* NULL if and only if uninitialized. */
};
#ifdef HAVE_PTHREAD_SPIN_LOCK
struct OVS_LOCKABLE ovs_spin {
pthread_spinlock_t lock;
const char *where; /* NULL if and only if uninitialized. */
};
#endif
/* "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 *mutex)
OVS_REQUIRES(mutex);
#ifdef HAVE_PTHREAD_SPIN_LOCK
void ovs_spin_init(const struct ovs_spin *);
void ovs_spin_destroy(const struct ovs_spin *);
void ovs_spin_unlock(const struct ovs_spin *spin) OVS_RELEASES(spin);
void ovs_spin_lock_at(const struct ovs_spin *spin, const char *where)
OVS_ACQUIRES(spin);
#define ovs_spin_lock(spin) \
ovs_spin_lock_at(spin, OVS_SOURCE_LOCATOR)
int ovs_spin_trylock_at(const struct ovs_spin *spin, const char *where)
OVS_TRY_LOCK(0, spin);
#define ovs_spin_trylock(spin) \
ovs_spin_trylock_at(spin, OVS_SOURCE_LOCATOR)
#endif
/* 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));
}
#ifdef __cplusplus
}
#endif
#endif /* ovs-thread.h */
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