2 * Copyright (c) 2013 Nicira, Inc.
4 * Licensed under the Apache License, Version 2.0 (the "License");
5 * you may not use this file except in compliance with the License.
6 * You may obtain a copy of the License at:
8 * http://www.apache.org/licenses/LICENSE-2.0
10 * Unless required by applicable law or agreed to in writing, software
11 * distributed under the License is distributed on an "AS IS" BASIS,
12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13 * See the License for the specific language governing permissions and
14 * limitations under the License.
18 #define OVS_THREAD_H 1
22 #include <sys/types.h>
23 #include "ovs-atomic.h"
28 struct OVS_LOCKABLE ovs_mutex {
33 /* "struct ovs_mutex" initializers:
35 * - OVS_MUTEX_INITIALIZER: common case.
37 * - OVS_ADAPTIVE_MUTEX_INITIALIZER for a mutex that spins briefly then goes
38 * to sleeps after some number of iterations.
40 * - OVS_ERRORCHECK_MUTEX_INITIALIZER for a mutex that is used for
42 #define OVS_MUTEX_INITIALIZER { PTHREAD_MUTEX_INITIALIZER, NULL }
43 #ifdef PTHREAD_ADAPTIVE_MUTEX_INITIALIZER_NP
44 #define OVS_ADAPTIVE_MUTEX_INITIALIZER \
45 { PTHREAD_ADAPTIVE_MUTEX_INITIALIZER_NP, NULL }
47 #define OVS_ADAPTIVE_MUTEX_INITIALIZER OVS_MUTEX_INITIALIZER
49 #ifdef PTHREAD_ERRORCHECK_MUTEX_INITIALIZER_NP
50 #define OVS_ERRORCHECK_MUTEX_INITIALIZER \
51 { PTHREAD_ERRORCHECK_MUTEX_INITIALIZER_NP, NULL }
53 #define OVS_ERRORCHECK_MUTEX_INITIALIZER OVS_MUTEX_INITIALIZER
56 /* Mutex types, suitable for use with pthread_mutexattr_settype().
57 * There is only one nonstandard type:
59 * - PTHREAD_MUTEX_ADAPTIVE_NP, the type used for
60 * OVS_ADAPTIVE_MUTEX_INITIALIZER. */
61 #ifdef PTHREAD_ADAPTIVE_MUTEX_INITIALIZER_NP
62 #define OVS_MUTEX_ADAPTIVE PTHREAD_MUTEX_ADAPTIVE_NP
64 #define OVS_MUTEX_ADAPTIVE PTHREAD_MUTEX_NORMAL
67 /* ovs_mutex functions analogous to pthread_mutex_*() functions.
69 * Most of these functions abort the process with an error message on any
70 * error. ovs_mutex_trylock() is an exception: it passes through a 0 or EBUSY
71 * return value to the caller and aborts on any other error. */
72 void ovs_mutex_init(const struct ovs_mutex *, int type);
73 void ovs_mutex_destroy(const struct ovs_mutex *);
74 void ovs_mutex_unlock(const struct ovs_mutex *mutex) OVS_RELEASES(mutex);
75 void ovs_mutex_lock_at(const struct ovs_mutex *mutex, const char *where)
77 #define ovs_mutex_lock(mutex) \
78 ovs_mutex_lock_at(mutex, SOURCE_LOCATOR)
80 int ovs_mutex_trylock_at(const struct ovs_mutex *mutex, const char *where)
81 OVS_TRY_LOCK(0, mutex);
82 #define ovs_mutex_trylock(mutex) \
83 ovs_mutex_trylock_at(mutex, SOURCE_LOCATOR)
85 void ovs_mutex_cond_wait(pthread_cond_t *, const struct ovs_mutex *);
87 /* Wrappers for pthread_mutexattr_*() that abort the process on any error. */
88 void xpthread_mutexattr_init(pthread_mutexattr_t *);
89 void xpthread_mutexattr_destroy(pthread_mutexattr_t *);
90 void xpthread_mutexattr_settype(pthread_mutexattr_t *, int type);
91 void xpthread_mutexattr_gettype(pthread_mutexattr_t *, int *typep);
93 /* Read-write lock. */
94 struct OVS_LOCKABLE ovs_rwlock {
95 pthread_rwlock_t lock;
100 #define OVS_RWLOCK_INITIALIZER { PTHREAD_RWLOCK_INITIALIZER, NULL }
102 /* ovs_rwlock functions analogous to pthread_rwlock_*() functions.
104 * Most of these functions abort the process with an error message on any
105 * error. The "trylock" functions are exception: they pass through a 0 or
106 * EBUSY return value to the caller and abort on any other error. */
107 void ovs_rwlock_init(const struct ovs_rwlock *);
108 void ovs_rwlock_destroy(const struct ovs_rwlock *);
109 void ovs_rwlock_unlock(const struct ovs_rwlock *rwlock) OVS_RELEASES(rwlock);
111 void ovs_rwlock_wrlock_at(const struct ovs_rwlock *rwlock, const char *where)
112 OVS_ACQ_WRLOCK(rwlock);
113 #define ovs_rwlock_wrlock(rwlock) \
114 ovs_rwlock_wrlock_at(rwlock, SOURCE_LOCATOR);
116 int ovs_rwlock_trywrlock_at(const struct ovs_rwlock *rwlock, const char *where)
117 OVS_TRY_WRLOCK(0, rwlock);
118 #define ovs_rwlock_trywrlock(rwlock) \
119 ovs_rwlock_trywrlock_at(rwlock, SOURCE_LOCATOR)
121 void ovs_rwlock_rdlock_at(const struct ovs_rwlock *rwlock, const char *where)
122 OVS_ACQ_RDLOCK(rwlock);
123 #define ovs_rwlock_rdlock(rwlock) \
124 ovs_rwlock_rdlock_at(rwlock, SOURCE_LOCATOR);
126 int ovs_rwlock_tryrdlock_at(const struct ovs_rwlock *rwlock, const char *where)
127 OVS_TRY_RDLOCK(0, rwlock);
128 #define ovs_rwlock_tryrdlock(rwlock) \
129 ovs_rwlock_tryrdlock_at(rwlock, SOURCE_LOCATOR)
131 /* Wrappers for xpthread_cond_*() that abort the process on any error.
133 * Use ovs_mutex_cond_wait() to wait for a condition. */
134 void xpthread_cond_init(pthread_cond_t *, pthread_condattr_t *);
135 void xpthread_cond_destroy(pthread_cond_t *);
136 void xpthread_cond_signal(pthread_cond_t *);
137 void xpthread_cond_broadcast(pthread_cond_t *);
140 /* Replace these functions by the macros already defined in the <pthread.h>
141 * annotations, because the macro definitions have correct semantics for the
142 * conditional acquisition that can't be captured in a function annotation.
143 * The difference in semantics from pthread_*() to xpthread_*() does not matter
144 * because sparse is not a compiler. */
145 #define xpthread_mutex_trylock pthread_mutex_trylock
146 #define xpthread_rwlock_tryrdlock pthread_rwlock_tryrdlock
147 #define xpthread_rwlock_trywrlock pthread_rwlock_trywrlock
150 void xpthread_key_create(pthread_key_t *, void (*destructor)(void *));
152 void xpthread_create(pthread_t *, pthread_attr_t *, void *(*)(void *), void *);
156 * Multiple forms of per-thread data exist, each with its own pluses and
159 * - POSIX per-thread data via pthread_key_t is portable to any pthreads
160 * implementation, and allows a destructor function to be defined. It
161 * only (directly) supports per-thread pointers, which are always
162 * initialized to NULL. It requires once-only allocation of a
163 * pthread_key_t value. It is relatively slow.
165 * - The thread_local feature newly defined in C11 <threads.h> works with
166 * any data type and initializer, and it is fast. thread_local does not
167 * require once-only initialization like pthread_key_t. C11 does not
168 * define what happens if one attempts to access a thread_local object
169 * from a thread other than the one to which that object belongs. There
170 * is no provision to call a user-specified destructor when a thread
173 * - The __thread keyword is a GCC extension similar to thread_local but
174 * with a longer history. __thread is not portable to every GCC version
175 * or environment. __thread does not restrict the use of a thread-local
176 * object outside its own thread.
178 * Here's a handy summary:
180 * pthread_key_t thread_local __thread
181 * ------------- ------------ -------------
182 * portability high low medium
183 * speed low high high
184 * supports destructors? yes no no
185 * needs key allocation? yes no no
186 * arbitrary initializer? no yes yes
187 * cross-thread access? yes no yes
190 /* DEFINE_PER_THREAD_DATA(TYPE, NAME, INITIALIZER).
192 * One should prefer to use POSIX per-thread data, via pthread_key_t, when its
193 * performance is acceptable, because of its portability (see the table above).
194 * This macro is an alternatives that takes advantage of thread_local (and
195 * __thread), for its performance, when it is available, and falls back to
196 * POSIX per-thread data otherwise.
198 * Defines per-thread variable NAME with the given TYPE, initialized to
199 * INITIALIZER (which must be valid as an initializer for a variable with
202 * The public interface to the variable is:
204 * TYPE *NAME_get(void)
205 * TYPE *NAME_get_unsafe(void)
207 * Returns the address of this thread's instance of NAME.
209 * Use NAME_get() in a context where this might be the first use of the
210 * per-thread variable in the program. Use NAME_get_unsafe(), which
211 * avoids a conditional test and is thus slightly faster, in a context
212 * where one knows that NAME_get() has already been called previously.
214 * There is no "NAME_set()" (or "NAME_set_unsafe()") function. To set the
215 * value of the per-thread variable, dereference the pointer returned by
216 * TYPE_get() or TYPE_get_unsafe(), e.g. *TYPE_get() = 0.
218 #if HAVE_THREAD_LOCAL || HAVE___THREAD
220 #if HAVE_THREAD_LOCAL
223 #define thread_local __thread
228 #define DEFINE_PER_THREAD_DATA(TYPE, NAME, ...) \
229 typedef TYPE NAME##_type; \
230 static thread_local NAME##_type NAME##_var = __VA_ARGS__; \
232 static NAME##_type * \
233 NAME##_get_unsafe(void) \
235 return &NAME##_var; \
238 static NAME##_type * \
241 return NAME##_get_unsafe(); \
243 #else /* no C implementation support for thread-local storage */
244 #define DEFINE_PER_THREAD_DATA(TYPE, NAME, ...) \
245 typedef TYPE NAME##_type; \
246 static pthread_key_t NAME##_key; \
248 static NAME##_type * \
249 NAME##_get_unsafe(void) \
251 return pthread_getspecific(NAME##_key); \
255 NAME##_once_init(void) \
257 if (pthread_key_create(&NAME##_key, free)) { \
262 static NAME##_type * \
265 static pthread_once_t once = PTHREAD_ONCE_INIT; \
266 NAME##_type *value; \
268 pthread_once(&once, NAME##_once_init); \
269 value = NAME##_get_unsafe(); \
271 static const NAME##_type initial_value = __VA_ARGS__; \
273 value = xmalloc(sizeof *value); \
274 *value = initial_value; \
275 pthread_setspecific(NAME##_key, value); \
281 /* DEFINE_PER_THREAD_MALLOCED_DATA(TYPE, NAME).
283 * This is a simple wrapper around POSIX per-thread data primitives. It
284 * defines per-thread variable NAME with the given TYPE, which must be a
285 * pointer type. In each thread, the per-thread variable is initialized to
286 * NULL. When a thread terminates, the variable is freed with free().
288 * The public interface to the variable is:
290 * TYPE NAME_get(void)
291 * TYPE NAME_get_unsafe(void)
293 * Returns the value of per-thread variable NAME in this thread.
295 * Use NAME_get() in a context where this might be the first use of the
296 * per-thread variable in the program. Use NAME_get_unsafe(), which
297 * avoids a conditional test and is thus slightly faster, in a context
298 * where one knows that NAME_get() has already been called previously.
300 * TYPE NAME_set(TYPE new_value)
301 * TYPE NAME_set_unsafe(TYPE new_value)
303 * Sets the value of per-thread variable NAME to 'new_value' in this
304 * thread, and returns its previous value.
306 * Use NAME_set() in a context where this might be the first use of the
307 * per-thread variable in the program. Use NAME_set_unsafe(), which
308 * avoids a conditional test and is thus slightly faster, in a context
309 * where one knows that NAME_set() has already been called previously.
311 #define DEFINE_PER_THREAD_MALLOCED_DATA(TYPE, NAME) \
312 static pthread_key_t NAME##_key; \
315 NAME##_once_init(void) \
317 if (pthread_key_create(&NAME##_key, free)) { \
325 static pthread_once_t once = PTHREAD_ONCE_INIT; \
326 pthread_once(&once, NAME##_once_init); \
330 NAME##_get_unsafe(void) \
332 return pthread_getspecific(NAME##_key); \
335 static OVS_UNUSED TYPE \
339 return NAME##_get_unsafe(); \
343 NAME##_set_unsafe(TYPE value) \
345 TYPE old_value = NAME##_get_unsafe(); \
346 pthread_setspecific(NAME##_key, value); \
350 static OVS_UNUSED TYPE \
351 NAME##_set(TYPE value) \
354 return NAME##_set_unsafe(value); \
357 /* Convenient once-only execution.
363 * POSIX provides pthread_once_t and pthread_once() as primitives for running a
364 * set of code only once per process execution. They are used like this:
366 * static void run_once(void) { ...initialization... }
367 * static pthread_once_t once = PTHREAD_ONCE_INIT;
369 * pthread_once(&once, run_once);
371 * pthread_once() does not allow passing any parameters to the initialization
372 * function, which is often inconvenient, because it means that the function
373 * can only access data declared at file scope.
379 * Use ovsthread_once, like this, instead:
381 * static struct ovsthread_once once = OVSTHREAD_ONCE_INITIALIZER;
383 * if (ovsthread_once_start(&once)) {
384 * ...initialization...
385 * ovsthread_once_done(&once);
389 struct ovsthread_once {
391 struct ovs_mutex mutex;
394 #define OVSTHREAD_ONCE_INITIALIZER \
396 ATOMIC_VAR_INIT(false), \
397 OVS_ADAPTIVE_MUTEX_INITIALIZER, \
400 static inline bool ovsthread_once_start(struct ovsthread_once *once)
401 OVS_TRY_LOCK(true, &once->mutex);
402 void ovsthread_once_done(struct ovsthread_once *once)
403 OVS_RELEASES(&once->mutex);
405 bool ovsthread_once_start__(struct ovsthread_once *once)
406 OVS_TRY_LOCK(false, &once->mutex);
409 ovsthread_once_is_done__(const struct ovsthread_once *once)
413 atomic_read_explicit(&once->done, &done, memory_order_relaxed);
417 /* Returns true if this is the first call to ovsthread_once_start() for
418 * 'once'. In this case, the caller should perform whatever initialization
419 * actions it needs to do, then call ovsthread_once_done() for 'once'.
421 * Returns false if this is not the first call to ovsthread_once_start() for
422 * 'once'. In this case, the call will not return until after
423 * ovsthread_once_done() has been called. */
425 ovsthread_once_start(struct ovsthread_once *once)
427 return OVS_UNLIKELY(!ovsthread_once_is_done__(once)
428 && !ovsthread_once_start__(once));
432 #define ovsthread_once_start(ONCE) \
433 ((ONCE)->done ? false : ({ OVS_MACRO_LOCK((&ONCE->mutex)); true; }))
436 void assert_single_threaded_at(const char *where);
437 #define assert_single_threaded() assert_single_threaded_at(SOURCE_LOCATOR)
439 pid_t xfork_at(const char *where);
440 #define xfork() xfork_at(SOURCE_LOCATOR)
442 void forbid_forking(const char *reason);
445 #endif /* ovs-thread.h */