2 * Copyright (c) 2013, 2014 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" initializer. */
34 #ifdef PTHREAD_ERRORCHECK_MUTEX_INITIALIZER_NP
35 #define OVS_MUTEX_INITIALIZER { PTHREAD_ERRORCHECK_MUTEX_INITIALIZER_NP, NULL }
37 #define OVS_MUTEX_INITIALIZER { PTHREAD_MUTEX_INITIALIZER, NULL }
40 #ifdef PTHREAD_ADAPTIVE_MUTEX_INITIALIZER_NP
41 #define OVS_ADAPTIVE_MUTEX_INITIALIZER \
42 { PTHREAD_ADAPTIVE_MUTEX_INITIALIZER_NP, NULL }
44 #define OVS_ADAPTIVE_MUTEX_INITIALIZER OVS_MUTEX_INITIALIZER
47 /* ovs_mutex functions analogous to pthread_mutex_*() functions.
49 * Most of these functions abort the process with an error message on any
50 * error. ovs_mutex_trylock() is an exception: it passes through a 0 or EBUSY
51 * return value to the caller and aborts on any other error. */
52 void ovs_mutex_init(const struct ovs_mutex *);
53 void ovs_mutex_init_recursive(const struct ovs_mutex *);
54 void ovs_mutex_init_adaptive(const struct ovs_mutex *);
55 void ovs_mutex_destroy(const struct ovs_mutex *);
56 void ovs_mutex_unlock(const struct ovs_mutex *mutex) OVS_RELEASES(mutex);
57 void ovs_mutex_lock_at(const struct ovs_mutex *mutex, const char *where)
59 #define ovs_mutex_lock(mutex) \
60 ovs_mutex_lock_at(mutex, SOURCE_LOCATOR)
62 int ovs_mutex_trylock_at(const struct ovs_mutex *mutex, const char *where)
63 OVS_TRY_LOCK(0, mutex);
64 #define ovs_mutex_trylock(mutex) \
65 ovs_mutex_trylock_at(mutex, SOURCE_LOCATOR)
67 void ovs_mutex_cond_wait(pthread_cond_t *, const struct ovs_mutex *);
69 /* Wrappers for pthread_mutex_*() that abort the process on any error.
70 * This is still needed when ovs-atomic-pthreads.h is used. */
71 void xpthread_mutex_lock(pthread_mutex_t *mutex);
72 void xpthread_mutex_unlock(pthread_mutex_t *mutex);
74 /* Wrappers for pthread_mutexattr_*() that abort the process on any error. */
75 void xpthread_mutexattr_init(pthread_mutexattr_t *);
76 void xpthread_mutexattr_destroy(pthread_mutexattr_t *);
77 void xpthread_mutexattr_settype(pthread_mutexattr_t *, int type);
78 void xpthread_mutexattr_gettype(pthread_mutexattr_t *, int *typep);
80 /* Read-write lock. */
81 struct OVS_LOCKABLE ovs_rwlock {
82 pthread_rwlock_t lock;
87 #define OVS_RWLOCK_INITIALIZER { PTHREAD_RWLOCK_INITIALIZER, NULL }
89 /* ovs_rwlock functions analogous to pthread_rwlock_*() functions.
91 * Most of these functions abort the process with an error message on any
92 * error. The "trylock" functions are exception: they pass through a 0 or
93 * EBUSY return value to the caller and abort on any other error. */
94 void ovs_rwlock_init(const struct ovs_rwlock *);
95 void ovs_rwlock_destroy(const struct ovs_rwlock *);
96 void ovs_rwlock_unlock(const struct ovs_rwlock *rwlock) OVS_RELEASES(rwlock);
98 void ovs_rwlock_wrlock_at(const struct ovs_rwlock *rwlock, const char *where)
99 OVS_ACQ_WRLOCK(rwlock);
100 #define ovs_rwlock_wrlock(rwlock) \
101 ovs_rwlock_wrlock_at(rwlock, SOURCE_LOCATOR)
103 int ovs_rwlock_trywrlock_at(const struct ovs_rwlock *rwlock, const char *where)
104 OVS_TRY_WRLOCK(0, rwlock);
105 #define ovs_rwlock_trywrlock(rwlock) \
106 ovs_rwlock_trywrlock_at(rwlock, SOURCE_LOCATOR)
108 void ovs_rwlock_rdlock_at(const struct ovs_rwlock *rwlock, const char *where)
109 OVS_ACQ_RDLOCK(rwlock);
110 #define ovs_rwlock_rdlock(rwlock) \
111 ovs_rwlock_rdlock_at(rwlock, SOURCE_LOCATOR)
113 int ovs_rwlock_tryrdlock_at(const struct ovs_rwlock *rwlock, const char *where)
114 OVS_TRY_RDLOCK(0, rwlock);
115 #define ovs_rwlock_tryrdlock(rwlock) \
116 ovs_rwlock_tryrdlock_at(rwlock, SOURCE_LOCATOR)
118 /* Wrappers for xpthread_cond_*() that abort the process on any error.
120 * Use ovs_mutex_cond_wait() to wait for a condition. */
121 void xpthread_cond_init(pthread_cond_t *, pthread_condattr_t *);
122 void xpthread_cond_destroy(pthread_cond_t *);
123 void xpthread_cond_signal(pthread_cond_t *);
124 void xpthread_cond_broadcast(pthread_cond_t *);
126 void xpthread_key_create(pthread_key_t *, void (*destructor)(void *));
127 void xpthread_key_delete(pthread_key_t);
128 void xpthread_setspecific(pthread_key_t, const void *);
130 void xpthread_create(pthread_t *, pthread_attr_t *, void *(*)(void *), void *);
131 void xpthread_join(pthread_t, void **);
139 * Multiple forms of standard per-thread data exist, each with its own pluses
140 * and minuses. In general, if one of these forms is appropriate, then it's a
141 * good idea to use it:
143 * - POSIX per-thread data via pthread_key_t is portable to any pthreads
144 * implementation, and allows a destructor function to be defined. It
145 * only (directly) supports per-thread pointers, which are always
146 * initialized to NULL. It requires once-only allocation of a
147 * pthread_key_t value. It is relatively slow. Typically few
148 * "pthread_key_t"s are available (POSIX requires only at least 128,
149 * glibc supplies only 1024).
151 * - The thread_local feature newly defined in C11 <threads.h> works with
152 * any data type and initializer, and it is fast. thread_local does not
153 * require once-only initialization like pthread_key_t. C11 does not
154 * define what happens if one attempts to access a thread_local object
155 * from a thread other than the one to which that object belongs. There
156 * is no provision to call a user-specified destructor when a thread
157 * ends. Typical implementations allow for an arbitrary amount of
158 * thread_local storage, but statically allocated only.
160 * - The __thread keyword is a GCC extension similar to thread_local but
161 * with a longer history. __thread is not portable to every GCC version
162 * or environment. __thread does not restrict the use of a thread-local
163 * object outside its own thread.
165 * Here's a handy summary:
167 * pthread_key_t thread_local __thread
168 * ------------- ------------ -------------
169 * portability high low medium
170 * speed low high high
171 * supports destructors? yes no no
172 * needs key allocation? yes no no
173 * arbitrary initializer? no yes yes
174 * cross-thread access? yes no yes
175 * amount available? few arbitrary arbitrary
176 * dynamically allocated? yes no no
182 * OVS provides some extensions and wrappers:
184 * - In a situation where the performance of thread_local or __thread is
185 * desirable, but portability is required, DEFINE_STATIC_PER_THREAD_DATA
186 * and DECLARE_EXTERN_PER_THREAD_DATA/DEFINE_EXTERN_PER_THREAD_DATA may
187 * be appropriate (see below).
189 * - DEFINE_PER_THREAD_MALLOCED_DATA can be convenient for simple
190 * per-thread malloc()'d buffers.
192 * - struct ovs_tsd provides an alternative to pthread_key_t that isn't
193 * limited to a small number of keys.
196 /* For static data, use this macro in a source file:
198 * DEFINE_STATIC_PER_THREAD_DATA(TYPE, NAME, INITIALIZER).
200 * For global data, "declare" the data in the header and "define" it in
201 * the source file, with:
203 * DECLARE_EXTERN_PER_THREAD_DATA(TYPE, NAME).
204 * DEFINE_EXTERN_PER_THREAD_DATA(NAME, INITIALIZER).
206 * One should prefer to use POSIX per-thread data, via pthread_key_t, when its
207 * performance is acceptable, because of its portability (see the table above).
208 * This macro is an alternatives that takes advantage of thread_local (and
209 * __thread), for its performance, when it is available, and falls back to
210 * POSIX per-thread data otherwise.
212 * Defines per-thread variable NAME with the given TYPE, initialized to
213 * INITIALIZER (which must be valid as an initializer for a variable with
216 * The public interface to the variable is:
218 * TYPE *NAME_get(void)
219 * TYPE *NAME_get_unsafe(void)
221 * Returns the address of this thread's instance of NAME.
223 * Use NAME_get() in a context where this might be the first use of the
224 * per-thread variable in the program. Use NAME_get_unsafe(), which
225 * avoids a conditional test and is thus slightly faster, in a context
226 * where one knows that NAME_get() has already been called previously.
228 * There is no "NAME_set()" (or "NAME_set_unsafe()") function. To set the
229 * value of the per-thread variable, dereference the pointer returned by
230 * TYPE_get() or TYPE_get_unsafe(), e.g. *TYPE_get() = 0.
232 #if HAVE_THREAD_LOCAL || HAVE___THREAD
234 #if HAVE_THREAD_LOCAL
237 #define thread_local __thread
242 #define DEFINE_STATIC_PER_THREAD_DATA(TYPE, NAME, ...) \
243 typedef TYPE NAME##_type; \
245 static NAME##_type * \
246 NAME##_get_unsafe(void) \
248 static thread_local NAME##_type var = __VA_ARGS__; \
252 static NAME##_type * \
255 return NAME##_get_unsafe(); \
257 #define DECLARE_EXTERN_PER_THREAD_DATA(TYPE, NAME) \
258 typedef TYPE NAME##_type; \
259 extern thread_local NAME##_type NAME##_var; \
261 static inline NAME##_type * \
262 NAME##_get_unsafe(void) \
264 return &NAME##_var; \
267 static inline NAME##_type * \
270 return NAME##_get_unsafe(); \
272 #define DEFINE_EXTERN_PER_THREAD_DATA(NAME, ...) \
273 thread_local NAME##_type NAME##_var = __VA_ARGS__;
274 #else /* no C implementation support for thread-local storage */
275 #define DEFINE_STATIC_PER_THREAD_DATA(TYPE, NAME, ...) \
276 typedef TYPE NAME##_type; \
277 static pthread_key_t NAME##_key; \
279 static NAME##_type * \
280 NAME##_get_unsafe(void) \
282 return pthread_getspecific(NAME##_key); \
286 NAME##_once_init(void) \
288 if (pthread_key_create(&NAME##_key, free)) { \
293 static NAME##_type * \
296 static pthread_once_t once = PTHREAD_ONCE_INIT; \
297 NAME##_type *value; \
299 pthread_once(&once, NAME##_once_init); \
300 value = NAME##_get_unsafe(); \
302 static const NAME##_type initial_value = __VA_ARGS__; \
304 value = malloc(sizeof *value); \
305 if (value == NULL) { \
308 *value = initial_value; \
309 xpthread_setspecific(NAME##_key, value); \
313 #define DECLARE_EXTERN_PER_THREAD_DATA(TYPE, NAME) \
314 typedef TYPE NAME##_type; \
315 static pthread_key_t NAME##_key; \
317 static inline NAME##_type * \
318 NAME##_get_unsafe(void) \
320 return pthread_getspecific(NAME##_key); \
323 NAME##_type *NAME##_get(void);
324 #define DEFINE_EXTERN_PER_THREAD_DATA(NAME, ...) \
326 NAME##_once_init(void) \
328 if (pthread_key_create(&NAME##_key, free)) { \
336 static pthread_once_t once = PTHREAD_ONCE_INIT; \
337 NAME##_type *value; \
339 pthread_once(&once, NAME##_once_init); \
340 value = NAME##_get_unsafe(); \
342 static const NAME##_type initial_value = __VA_ARGS__; \
344 value = malloc(sizeof *value); \
345 if (value == NULL) { \
348 *value = initial_value; \
349 xpthread_setspecific(NAME##_key, value); \
355 /* DEFINE_PER_THREAD_MALLOCED_DATA(TYPE, NAME).
357 * This is a simple wrapper around POSIX per-thread data primitives. It
358 * defines per-thread variable NAME with the given TYPE, which must be a
359 * pointer type. In each thread, the per-thread variable is initialized to
360 * NULL. When a thread terminates, the variable is freed with free().
362 * The public interface to the variable is:
364 * TYPE NAME_get(void)
365 * TYPE NAME_get_unsafe(void)
367 * Returns the value of per-thread variable NAME in this thread.
369 * Use NAME_get() in a context where this might be the first use of the
370 * per-thread variable in the program. Use NAME_get_unsafe(), which
371 * avoids a conditional test and is thus slightly faster, in a context
372 * where one knows that NAME_get() has already been called previously.
374 * TYPE NAME_set(TYPE new_value)
375 * TYPE NAME_set_unsafe(TYPE new_value)
377 * Sets the value of per-thread variable NAME to 'new_value' in this
378 * thread, and returns its previous value.
380 * Use NAME_set() in a context where this might be the first use of the
381 * per-thread variable in the program. Use NAME_set_unsafe(), which
382 * avoids a conditional test and is thus slightly faster, in a context
383 * where one knows that NAME_set() has already been called previously.
385 #define DEFINE_PER_THREAD_MALLOCED_DATA(TYPE, NAME) \
386 static pthread_key_t NAME##_key; \
389 NAME##_once_init(void) \
391 if (pthread_key_create(&NAME##_key, free)) { \
399 static pthread_once_t once = PTHREAD_ONCE_INIT; \
400 pthread_once(&once, NAME##_once_init); \
404 NAME##_get_unsafe(void) \
406 return pthread_getspecific(NAME##_key); \
409 static OVS_UNUSED TYPE \
413 return NAME##_get_unsafe(); \
417 NAME##_set_unsafe(TYPE value) \
419 TYPE old_value = NAME##_get_unsafe(); \
420 xpthread_setspecific(NAME##_key, value); \
424 static OVS_UNUSED TYPE \
425 NAME##_set(TYPE value) \
428 return NAME##_set_unsafe(value); \
431 /* Dynamically allocated thread-specific data with lots of slots.
433 * pthread_key_t can provide as few as 128 pieces of thread-specific data (even
434 * glibc is limited to 1,024). Thus, one must be careful to allocate only a
435 * few keys globally. One cannot, for example, allocate a key for every
436 * instance of a data structure if there might be an arbitrary number of those
439 * This API is similar to the pthread one (simply search and replace pthread_
440 * by ovsthread_) but it a much larger limit that can be raised if necessary
441 * (by recompiling). Thus, one may more freely use this form of
442 * thread-specific data.
444 * ovsthread_key_t also differs from pthread_key_t in the following ways:
446 * - Destructors must not access thread-specific data (via ovsthread_key).
448 * - The pthread_key_t API allows concurrently exiting threads to start
449 * executing the destructor after pthread_key_delete() returns. The
450 * ovsthread_key_t API guarantees that, when ovsthread_key_delete()
451 * returns, all destructors have returned and no new ones will start
454 typedef struct ovsthread_key *ovsthread_key_t;
456 void ovsthread_key_create(ovsthread_key_t *, void (*destructor)(void *));
457 void ovsthread_key_delete(ovsthread_key_t);
459 void ovsthread_setspecific(ovsthread_key_t, const void *);
460 void *ovsthread_getspecific(ovsthread_key_t);
462 /* Convenient once-only execution.
468 * POSIX provides pthread_once_t and pthread_once() as primitives for running a
469 * set of code only once per process execution. They are used like this:
471 * static void run_once(void) { ...initialization... }
472 * static pthread_once_t once = PTHREAD_ONCE_INIT;
474 * pthread_once(&once, run_once);
476 * pthread_once() does not allow passing any parameters to the initialization
477 * function, which is often inconvenient, because it means that the function
478 * can only access data declared at file scope.
484 * Use ovsthread_once, like this, instead:
486 * static struct ovsthread_once once = OVSTHREAD_ONCE_INITIALIZER;
488 * if (ovsthread_once_start(&once)) {
489 * ...initialization...
490 * ovsthread_once_done(&once);
494 struct ovsthread_once {
496 struct ovs_mutex mutex;
499 #define OVSTHREAD_ONCE_INITIALIZER \
501 ATOMIC_VAR_INIT(false), \
502 OVS_MUTEX_INITIALIZER, \
505 static inline bool ovsthread_once_start(struct ovsthread_once *once)
506 OVS_TRY_LOCK(true, once->mutex);
507 void ovsthread_once_done(struct ovsthread_once *once)
508 OVS_RELEASES(once->mutex);
510 bool ovsthread_once_start__(struct ovsthread_once *once)
511 OVS_TRY_LOCK(false, once->mutex);
514 ovsthread_once_is_done__(struct ovsthread_once *once)
518 atomic_read_explicit(&once->done, &done, memory_order_relaxed);
522 /* Returns true if this is the first call to ovsthread_once_start() for
523 * 'once'. In this case, the caller should perform whatever initialization
524 * actions it needs to do, then call ovsthread_once_done() for 'once'.
526 * Returns false if this is not the first call to ovsthread_once_start() for
527 * 'once'. In this case, the call will not return until after
528 * ovsthread_once_done() has been called. */
530 ovsthread_once_start(struct ovsthread_once *once)
532 return OVS_UNLIKELY(!ovsthread_once_is_done__(once)
533 && !ovsthread_once_start__(once));
538 * pthread_t isn't so nice for some purposes. Its size and representation are
539 * implementation dependent, which means that there is no way to hash it.
540 * This thread ID avoids the problem.
543 DECLARE_EXTERN_PER_THREAD_DATA(unsigned int, ovsthread_id);
545 /* Returns a per-thread identifier unique within the lifetime of the
547 static inline unsigned int
548 ovsthread_id_self(void)
550 return *ovsthread_id_get();
553 /* Simulated global counter.
555 * Incrementing such a counter is meant to be cheaper than incrementing a
556 * global counter protected by a lock. It is probably more expensive than
557 * incrementing a truly thread-local variable, but such a variable has no
558 * straightforward way to get the sum.
564 * Fully thread-safe. */
566 struct ovsthread_counter *ovsthread_counter_create(void);
567 void ovsthread_counter_destroy(struct ovsthread_counter *);
568 void ovsthread_counter_inc(struct ovsthread_counter *, unsigned long long int);
569 unsigned long long int ovsthread_counter_read(
570 const struct ovsthread_counter *);
572 void assert_single_threaded_at(const char *where);
573 #define assert_single_threaded() assert_single_threaded_at(SOURCE_LOCATOR)
575 pid_t xfork_at(const char *where);
576 #define xfork() xfork_at(SOURCE_LOCATOR)
578 void forbid_forking(const char *reason);
581 /* Useful functions related to threading. */
583 int count_cpu_cores(void);
585 #endif /* ovs-thread.h */