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_mutex_*() that abort the process on any error.
88 * This is still needed when ovs-atomic-pthreads.h is used. */
89 void xpthread_mutex_lock(pthread_mutex_t *mutex);
90 void xpthread_mutex_unlock(pthread_mutex_t *mutex);
92 /* Wrappers for pthread_mutexattr_*() that abort the process on any error. */
93 void xpthread_mutexattr_init(pthread_mutexattr_t *);
94 void xpthread_mutexattr_destroy(pthread_mutexattr_t *);
95 void xpthread_mutexattr_settype(pthread_mutexattr_t *, int type);
96 void xpthread_mutexattr_gettype(pthread_mutexattr_t *, int *typep);
98 /* Read-write lock. */
99 struct OVS_LOCKABLE ovs_rwlock {
100 pthread_rwlock_t lock;
105 #define OVS_RWLOCK_INITIALIZER { PTHREAD_RWLOCK_INITIALIZER, NULL }
107 /* ovs_rwlock functions analogous to pthread_rwlock_*() functions.
109 * Most of these functions abort the process with an error message on any
110 * error. The "trylock" functions are exception: they pass through a 0 or
111 * EBUSY return value to the caller and abort on any other error. */
112 void ovs_rwlock_init(const struct ovs_rwlock *);
113 void ovs_rwlock_destroy(const struct ovs_rwlock *);
114 void ovs_rwlock_unlock(const struct ovs_rwlock *rwlock) OVS_RELEASES(rwlock);
116 void ovs_rwlock_wrlock_at(const struct ovs_rwlock *rwlock, const char *where)
117 OVS_ACQ_WRLOCK(rwlock);
118 #define ovs_rwlock_wrlock(rwlock) \
119 ovs_rwlock_wrlock_at(rwlock, SOURCE_LOCATOR);
121 int ovs_rwlock_trywrlock_at(const struct ovs_rwlock *rwlock, const char *where)
122 OVS_TRY_WRLOCK(0, rwlock);
123 #define ovs_rwlock_trywrlock(rwlock) \
124 ovs_rwlock_trywrlock_at(rwlock, SOURCE_LOCATOR)
126 void ovs_rwlock_rdlock_at(const struct ovs_rwlock *rwlock, const char *where)
127 OVS_ACQ_RDLOCK(rwlock);
128 #define ovs_rwlock_rdlock(rwlock) \
129 ovs_rwlock_rdlock_at(rwlock, SOURCE_LOCATOR);
131 int ovs_rwlock_tryrdlock_at(const struct ovs_rwlock *rwlock, const char *where)
132 OVS_TRY_RDLOCK(0, rwlock);
133 #define ovs_rwlock_tryrdlock(rwlock) \
134 ovs_rwlock_tryrdlock_at(rwlock, SOURCE_LOCATOR)
136 /* Wrappers for xpthread_cond_*() that abort the process on any error.
138 * Use ovs_mutex_cond_wait() to wait for a condition. */
139 void xpthread_cond_init(pthread_cond_t *, pthread_condattr_t *);
140 void xpthread_cond_destroy(pthread_cond_t *);
141 void xpthread_cond_signal(pthread_cond_t *);
142 void xpthread_cond_broadcast(pthread_cond_t *);
145 /* Replace these functions by the macros already defined in the <pthread.h>
146 * annotations, because the macro definitions have correct semantics for the
147 * conditional acquisition that can't be captured in a function annotation.
148 * The difference in semantics from pthread_*() to xpthread_*() does not matter
149 * because sparse is not a compiler. */
150 #define xpthread_mutex_trylock pthread_mutex_trylock
151 #define xpthread_rwlock_tryrdlock pthread_rwlock_tryrdlock
152 #define xpthread_rwlock_trywrlock pthread_rwlock_trywrlock
155 void xpthread_key_create(pthread_key_t *, void (*destructor)(void *));
157 void xpthread_create(pthread_t *, pthread_attr_t *, void *(*)(void *), void *);
161 * Multiple forms of per-thread data exist, each with its own pluses and
164 * - POSIX per-thread data via pthread_key_t is portable to any pthreads
165 * implementation, and allows a destructor function to be defined. It
166 * only (directly) supports per-thread pointers, which are always
167 * initialized to NULL. It requires once-only allocation of a
168 * pthread_key_t value. It is relatively slow.
170 * - The thread_local feature newly defined in C11 <threads.h> works with
171 * any data type and initializer, and it is fast. thread_local does not
172 * require once-only initialization like pthread_key_t. C11 does not
173 * define what happens if one attempts to access a thread_local object
174 * from a thread other than the one to which that object belongs. There
175 * is no provision to call a user-specified destructor when a thread
178 * - The __thread keyword is a GCC extension similar to thread_local but
179 * with a longer history. __thread is not portable to every GCC version
180 * or environment. __thread does not restrict the use of a thread-local
181 * object outside its own thread.
183 * Here's a handy summary:
185 * pthread_key_t thread_local __thread
186 * ------------- ------------ -------------
187 * portability high low medium
188 * speed low high high
189 * supports destructors? yes no no
190 * needs key allocation? yes no no
191 * arbitrary initializer? no yes yes
192 * cross-thread access? yes no yes
195 /* DEFINE_PER_THREAD_DATA(TYPE, NAME, INITIALIZER).
197 * One should prefer to use POSIX per-thread data, via pthread_key_t, when its
198 * performance is acceptable, because of its portability (see the table above).
199 * This macro is an alternatives that takes advantage of thread_local (and
200 * __thread), for its performance, when it is available, and falls back to
201 * POSIX per-thread data otherwise.
203 * Defines per-thread variable NAME with the given TYPE, initialized to
204 * INITIALIZER (which must be valid as an initializer for a variable with
207 * The public interface to the variable is:
209 * TYPE *NAME_get(void)
210 * TYPE *NAME_get_unsafe(void)
212 * Returns the address of this thread's instance of NAME.
214 * Use NAME_get() in a context where this might be the first use of the
215 * per-thread variable in the program. Use NAME_get_unsafe(), which
216 * avoids a conditional test and is thus slightly faster, in a context
217 * where one knows that NAME_get() has already been called previously.
219 * There is no "NAME_set()" (or "NAME_set_unsafe()") function. To set the
220 * value of the per-thread variable, dereference the pointer returned by
221 * TYPE_get() or TYPE_get_unsafe(), e.g. *TYPE_get() = 0.
223 #if HAVE_THREAD_LOCAL || HAVE___THREAD
225 #if HAVE_THREAD_LOCAL
228 #define thread_local __thread
233 #define DEFINE_PER_THREAD_DATA(TYPE, NAME, ...) \
234 typedef TYPE NAME##_type; \
235 static thread_local NAME##_type NAME##_var = __VA_ARGS__; \
237 static NAME##_type * \
238 NAME##_get_unsafe(void) \
240 return &NAME##_var; \
243 static NAME##_type * \
246 return NAME##_get_unsafe(); \
248 #else /* no C implementation support for thread-local storage */
249 #define DEFINE_PER_THREAD_DATA(TYPE, NAME, ...) \
250 typedef TYPE NAME##_type; \
251 static pthread_key_t NAME##_key; \
253 static NAME##_type * \
254 NAME##_get_unsafe(void) \
256 return pthread_getspecific(NAME##_key); \
260 NAME##_once_init(void) \
262 if (pthread_key_create(&NAME##_key, free)) { \
267 static NAME##_type * \
270 static pthread_once_t once = PTHREAD_ONCE_INIT; \
271 NAME##_type *value; \
273 pthread_once(&once, NAME##_once_init); \
274 value = NAME##_get_unsafe(); \
276 static const NAME##_type initial_value = __VA_ARGS__; \
278 value = xmalloc(sizeof *value); \
279 *value = initial_value; \
280 pthread_setspecific(NAME##_key, value); \
286 /* DEFINE_PER_THREAD_MALLOCED_DATA(TYPE, NAME).
288 * This is a simple wrapper around POSIX per-thread data primitives. It
289 * defines per-thread variable NAME with the given TYPE, which must be a
290 * pointer type. In each thread, the per-thread variable is initialized to
291 * NULL. When a thread terminates, the variable is freed with free().
293 * The public interface to the variable is:
295 * TYPE NAME_get(void)
296 * TYPE NAME_get_unsafe(void)
298 * Returns the value of per-thread variable NAME in this thread.
300 * Use NAME_get() in a context where this might be the first use of the
301 * per-thread variable in the program. Use NAME_get_unsafe(), which
302 * avoids a conditional test and is thus slightly faster, in a context
303 * where one knows that NAME_get() has already been called previously.
305 * TYPE NAME_set(TYPE new_value)
306 * TYPE NAME_set_unsafe(TYPE new_value)
308 * Sets the value of per-thread variable NAME to 'new_value' in this
309 * thread, and returns its previous value.
311 * Use NAME_set() in a context where this might be the first use of the
312 * per-thread variable in the program. Use NAME_set_unsafe(), which
313 * avoids a conditional test and is thus slightly faster, in a context
314 * where one knows that NAME_set() has already been called previously.
316 #define DEFINE_PER_THREAD_MALLOCED_DATA(TYPE, NAME) \
317 static pthread_key_t NAME##_key; \
320 NAME##_once_init(void) \
322 if (pthread_key_create(&NAME##_key, free)) { \
330 static pthread_once_t once = PTHREAD_ONCE_INIT; \
331 pthread_once(&once, NAME##_once_init); \
335 NAME##_get_unsafe(void) \
337 return pthread_getspecific(NAME##_key); \
340 static OVS_UNUSED TYPE \
344 return NAME##_get_unsafe(); \
348 NAME##_set_unsafe(TYPE value) \
350 TYPE old_value = NAME##_get_unsafe(); \
351 pthread_setspecific(NAME##_key, value); \
355 static OVS_UNUSED TYPE \
356 NAME##_set(TYPE value) \
359 return NAME##_set_unsafe(value); \
362 /* Convenient once-only execution.
368 * POSIX provides pthread_once_t and pthread_once() as primitives for running a
369 * set of code only once per process execution. They are used like this:
371 * static void run_once(void) { ...initialization... }
372 * static pthread_once_t once = PTHREAD_ONCE_INIT;
374 * pthread_once(&once, run_once);
376 * pthread_once() does not allow passing any parameters to the initialization
377 * function, which is often inconvenient, because it means that the function
378 * can only access data declared at file scope.
384 * Use ovsthread_once, like this, instead:
386 * static struct ovsthread_once once = OVSTHREAD_ONCE_INITIALIZER;
388 * if (ovsthread_once_start(&once)) {
389 * ...initialization...
390 * ovsthread_once_done(&once);
394 struct ovsthread_once {
396 struct ovs_mutex mutex;
399 #define OVSTHREAD_ONCE_INITIALIZER \
401 ATOMIC_VAR_INIT(false), \
402 OVS_ADAPTIVE_MUTEX_INITIALIZER, \
405 static inline bool ovsthread_once_start(struct ovsthread_once *once)
406 OVS_TRY_LOCK(true, &once->mutex);
407 void ovsthread_once_done(struct ovsthread_once *once)
408 OVS_RELEASES(&once->mutex);
410 bool ovsthread_once_start__(struct ovsthread_once *once)
411 OVS_TRY_LOCK(false, &once->mutex);
414 ovsthread_once_is_done__(const struct ovsthread_once *once)
418 atomic_read_explicit(&once->done, &done, memory_order_relaxed);
422 /* Returns true if this is the first call to ovsthread_once_start() for
423 * 'once'. In this case, the caller should perform whatever initialization
424 * actions it needs to do, then call ovsthread_once_done() for 'once'.
426 * Returns false if this is not the first call to ovsthread_once_start() for
427 * 'once'. In this case, the call will not return until after
428 * ovsthread_once_done() has been called. */
430 ovsthread_once_start(struct ovsthread_once *once)
432 return OVS_UNLIKELY(!ovsthread_once_is_done__(once)
433 && !ovsthread_once_start__(once));
437 #define ovsthread_once_start(ONCE) \
438 ((ONCE)->done ? false : ({ OVS_MACRO_LOCK((&ONCE->mutex)); true; }))
441 void assert_single_threaded_at(const char *where);
442 #define assert_single_threaded() assert_single_threaded_at(SOURCE_LOCATOR)
444 pid_t xfork_at(const char *where);
445 #define xfork() xfork_at(SOURCE_LOCATOR)
447 void forbid_forking(const char *reason);
450 #endif /* ovs-thread.h */