[mirror_ovs.git] / lib / ovs-thread.h

/*
 * Copyright (c) 2013 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 OVS_THREAD_H
#define OVS_THREAD_H 1

#include <pthread.h>
#include <stddef.h>
#include <sys/types.h>
#include "ovs-atomic.h"
#include "util.h"


/* Mutex. */
struct OVS_LOCKABLE ovs_mutex {
    pthread_mutex_t lock;
    const char *where;
};

/* "struct ovs_mutex" initializers:
 *
 *    - OVS_MUTEX_INITIALIZER: common case.
 *
 *    - OVS_ADAPTIVE_MUTEX_INITIALIZER for a mutex that spins briefly then goes
 *      to sleeps after some number of iterations.
 *
 *    - OVS_ERRORCHECK_MUTEX_INITIALIZER for a mutex that is used for
 *      error-checking. */
#define OVS_MUTEX_INITIALIZER { PTHREAD_MUTEX_INITIALIZER, NULL }
#ifdef PTHREAD_ADAPTIVE_MUTEX_INITIALIZER_NP
#define OVS_ADAPTIVE_MUTEX_INITIALIZER \
    { PTHREAD_ADAPTIVE_MUTEX_INITIALIZER_NP, NULL }
#else
#define OVS_ADAPTIVE_MUTEX_INITIALIZER OVS_MUTEX_INITIALIZER
#endif
#ifdef PTHREAD_ERRORCHECK_MUTEX_INITIALIZER_NP
#define OVS_ERRORCHECK_MUTEX_INITIALIZER \
    { PTHREAD_ERRORCHECK_MUTEX_INITIALIZER_NP, NULL }
#else
#define OVS_ERRORCHECK_MUTEX_INITIALIZER OVS_MUTEX_INITIALIZER
#endif
\f
/* Mutex types, suitable for use with pthread_mutexattr_settype().
 * There is only one nonstandard type:
 *
 *    - PTHREAD_MUTEX_ADAPTIVE_NP, the type used for
 *      OVS_ADAPTIVE_MUTEX_INITIALIZER. */
#ifdef PTHREAD_ADAPTIVE_MUTEX_INITIALIZER_NP
#define OVS_MUTEX_ADAPTIVE PTHREAD_MUTEX_ADAPTIVE_NP
#else
#define OVS_MUTEX_ADAPTIVE PTHREAD_MUTEX_NORMAL
#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 *, int type);
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, 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, SOURCE_LOCATOR)

void ovs_mutex_cond_wait(pthread_cond_t *, const struct ovs_mutex *);

/* Wrappers for pthread_mutex_*() that abort the process on any error.
 * This is still needed when ovs-atomic-pthreads.h is used. */
void xpthread_mutex_lock(pthread_mutex_t *mutex);
void xpthread_mutex_unlock(pthread_mutex_t *mutex);

/* Wrappers for pthread_mutexattr_*() that abort the process on any error. */
void xpthread_mutexattr_init(pthread_mutexattr_t *);
void xpthread_mutexattr_destroy(pthread_mutexattr_t *);
void xpthread_mutexattr_settype(pthread_mutexattr_t *, int type);
void xpthread_mutexattr_gettype(pthread_mutexattr_t *, int *typep);

/* Read-write lock. */
struct OVS_LOCKABLE ovs_rwlock {
    pthread_rwlock_t lock;
    const char *where;
};

/* Initializer. */
#define OVS_RWLOCK_INITIALIZER { PTHREAD_RWLOCK_INITIALIZER, NULL }

/* ovs_rwlock functions analogous to pthread_rwlock_*() functions.
 *
 * Most of these functions abort the process with an error message on any
 * error.  The "trylock" functions are exception: they pass through a 0 or
 * EBUSY return value to the caller and abort on any other error. */
void ovs_rwlock_init(const struct ovs_rwlock *);
void ovs_rwlock_destroy(const struct ovs_rwlock *);
void ovs_rwlock_unlock(const struct ovs_rwlock *rwlock) OVS_RELEASES(rwlock);

void ovs_rwlock_wrlock_at(const struct ovs_rwlock *rwlock, const char *where)
    OVS_ACQ_WRLOCK(rwlock);
#define ovs_rwlock_wrlock(rwlock) \
        ovs_rwlock_wrlock_at(rwlock, SOURCE_LOCATOR);

int ovs_rwlock_trywrlock_at(const struct ovs_rwlock *rwlock, const char *where)
    OVS_TRY_WRLOCK(0, rwlock);
#define ovs_rwlock_trywrlock(rwlock) \
    ovs_rwlock_trywrlock_at(rwlock, SOURCE_LOCATOR)

void ovs_rwlock_rdlock_at(const struct ovs_rwlock *rwlock, const char *where)
    OVS_ACQ_RDLOCK(rwlock);
#define ovs_rwlock_rdlock(rwlock) \
        ovs_rwlock_rdlock_at(rwlock, SOURCE_LOCATOR);

int ovs_rwlock_tryrdlock_at(const struct ovs_rwlock *rwlock, const char *where)
    OVS_TRY_RDLOCK(0, rwlock);
#define ovs_rwlock_tryrdlock(rwlock) \
        ovs_rwlock_tryrdlock_at(rwlock, SOURCE_LOCATOR)

/* Wrappers for xpthread_cond_*() that abort the process on any error.
 *
 * Use ovs_mutex_cond_wait() to wait for a condition. */
void xpthread_cond_init(pthread_cond_t *, pthread_condattr_t *);
void xpthread_cond_destroy(pthread_cond_t *);
void xpthread_cond_signal(pthread_cond_t *);
void xpthread_cond_broadcast(pthread_cond_t *);

#ifdef __CHECKER__
/* Replace these functions by the macros already defined in the <pthread.h>
 * annotations, because the macro definitions have correct semantics for the
 * conditional acquisition that can't be captured in a function annotation.
 * The difference in semantics from pthread_*() to xpthread_*() does not matter
 * because sparse is not a compiler. */
#define xpthread_mutex_trylock pthread_mutex_trylock
#define xpthread_rwlock_tryrdlock pthread_rwlock_tryrdlock
#define xpthread_rwlock_trywrlock pthread_rwlock_trywrlock
#endif

void xpthread_key_create(pthread_key_t *, void (*destructor)(void *));
void xpthread_setspecific(pthread_key_t, const void *);

void xpthread_create(pthread_t *, pthread_attr_t *, void *(*)(void *), void *);
\f
/* Per-thread data.
 *
 * Multiple forms of per-thread data exist, each with its own pluses and
 * minuses:
 *
 *     - POSIX per-thread data via pthread_key_t is portable to any pthreads
 *       implementation, and allows a destructor function to be defined.  It
 *       only (directly) supports per-thread pointers, which are always
 *       initialized to NULL.  It requires once-only allocation of a
 *       pthread_key_t value.  It is relatively slow.
 *
 *     - The thread_local feature newly defined in C11 <threads.h> works with
 *       any data type and initializer, and it is fast.  thread_local does not
 *       require once-only initialization like pthread_key_t.  C11 does not
 *       define what happens if one attempts to access a thread_local object
 *       from a thread other than the one to which that object belongs.  There
 *       is no provision to call a user-specified destructor when a thread
 *       ends.
 *
 *     - The __thread keyword is a GCC extension similar to thread_local but
 *       with a longer history.  __thread is not portable to every GCC version
 *       or environment.  __thread does not restrict the use of a thread-local
 *       object outside its own thread.
 *
 * Here's a handy summary:
 *
 *                     pthread_key_t     thread_local       __thread
 *                     -------------     ------------     -------------
 * portability             high               low             medium
 * speed                    low              high               high
 * supports destructors?    yes                no                 no
 * needs key allocation?    yes                no                 no
 * arbitrary initializer?    no               yes                yes
 * cross-thread access?     yes                no                yes
 */

/* For static data, use this macro in a source file:
 *
 *    DEFINE_STATIC_PER_THREAD_DATA(TYPE, NAME, INITIALIZER).
 *
 * For global data, "declare" the data in the header and "define" it in
 * the source file, with:
 *
 *    DECLARE_EXTERN_PER_THREAD_DATA(TYPE, NAME).
 *    DEFINE_EXTERN_PER_THREAD_DATA(NAME, INITIALIZER).
 *
 * One should prefer to use POSIX per-thread data, via pthread_key_t, when its
 * performance is acceptable, because of its portability (see the table above).
 * This macro is an alternatives that takes advantage of thread_local (and
 * __thread), for its performance, when it is available, and falls back to
 * POSIX per-thread data otherwise.
 *
 * Defines per-thread variable NAME with the given TYPE, initialized to
 * INITIALIZER (which must be valid as an initializer for a variable with
 * static lifetime).
 *
 * The public interface to the variable is:
 *
 *    TYPE *NAME_get(void)
 *    TYPE *NAME_get_unsafe(void)
 *
 *       Returns the address of this thread's instance of NAME.
 *
 *       Use NAME_get() in a context where this might be the first use of the
 *       per-thread variable in the program.  Use NAME_get_unsafe(), which
 *       avoids a conditional test and is thus slightly faster, in a context
 *       where one knows that NAME_get() has already been called previously.
 *
 * There is no "NAME_set()" (or "NAME_set_unsafe()") function.  To set the
 * value of the per-thread variable, dereference the pointer returned by
 * TYPE_get() or TYPE_get_unsafe(), e.g. *TYPE_get() = 0.
 */
#if HAVE_THREAD_LOCAL || HAVE___THREAD

#if HAVE_THREAD_LOCAL
#include <threads.h>
#elif HAVE___THREAD
#define thread_local __thread
#else
#error
#endif

#define DEFINE_STATIC_PER_THREAD_DATA(TYPE, NAME, ...)                  \
    typedef TYPE NAME##_type;                                           \
                                                                        \
    static NAME##_type *                                                \
    NAME##_get_unsafe(void)                                             \
    {                                                                   \
        static thread_local NAME##_type var = __VA_ARGS__;              \
        return &var;                                                    \
    }                                                                   \
                                                                        \
    static NAME##_type *                                                \
    NAME##_get(void)                                                    \
    {                                                                   \
        return NAME##_get_unsafe();                                     \
    }
#define DECLARE_EXTERN_PER_THREAD_DATA(TYPE, NAME)                      \
    typedef TYPE NAME##_type;                                           \
    extern thread_local NAME##_type NAME##_var;                         \
                                                                        \
    static inline NAME##_type *                                         \
    NAME##_get_unsafe(void)                                             \
    {                                                                   \
        return &NAME##_var;                                             \
    }                                                                   \
                                                                        \
    static inline NAME##_type *                                         \
    NAME##_get(void)                                                    \
    {                                                                   \
        return NAME##_get_unsafe();                                     \
    }
#define DEFINE_EXTERN_PER_THREAD_DATA(NAME, ...)         \
    thread_local NAME##_type NAME##_var = __VA_ARGS__;
#else  /* no C implementation support for thread-local storage  */
#define DEFINE_STATIC_PER_THREAD_DATA(TYPE, NAME, ...)                  \
    typedef TYPE NAME##_type;                                           \
    static pthread_key_t NAME##_key;                                    \
                                                                        \
    static NAME##_type *                                                \
    NAME##_get_unsafe(void)                                             \
    {                                                                   \
        return pthread_getspecific(NAME##_key);                         \
    }                                                                   \
                                                                        \
    static void                                                         \
    NAME##_once_init(void)                                              \
    {                                                                   \
        if (pthread_key_create(&NAME##_key, free)) {                    \
            abort();                                                    \
        }                                                               \
    }                                                                   \
                                                                        \
    static NAME##_type *                                                \
    NAME##_get(void)                                                    \
    {                                                                   \
        static pthread_once_t once = PTHREAD_ONCE_INIT;                 \
        NAME##_type *value;                                             \
                                                                        \
        pthread_once(&once, NAME##_once_init);                          \
        value = NAME##_get_unsafe();                                    \
        if (!value) {                                                   \
            static const NAME##_type initial_value = __VA_ARGS__;       \
                                                                        \
            value = xmalloc(sizeof *value);                             \
            *value = initial_value;                                     \
            xpthread_setspecific(NAME##_key, value);                    \
        }                                                               \
        return value;                                                   \
    }
#define DECLARE_EXTERN_PER_THREAD_DATA(TYPE, NAME)                      \
    typedef TYPE NAME##_type;                                           \
    static pthread_key_t NAME##_key;                                    \
                                                                        \
    static inline NAME##_type *                                         \
    NAME##_get_unsafe(void)                                             \
    {                                                                   \
        return pthread_getspecific(NAME##_key);                         \
    }                                                                   \
                                                                        \
    NAME##_type *NAME##_get(void);
#define DEFINE_EXTERN_PER_THREAD_DATA(NAME, ...)                        \
    static void                                                         \
    NAME##_once_init(void)                                              \
    {                                                                   \
        if (pthread_key_create(&NAME##_key, free)) {                    \
            abort();                                                    \
        }                                                               \
    }                                                                   \
                                                                        \
    NAME##_type *                                                       \
    NAME##_get(void)                                                    \
    {                                                                   \
        static pthread_once_t once = PTHREAD_ONCE_INIT;                 \
        NAME##_type *value;                                             \
                                                                        \
        pthread_once(&once, NAME##_once_init);                          \
        value = NAME##_get_unsafe();                                    \
        if (!value) {                                                   \
            static const NAME##_type initial_value = __VA_ARGS__;       \
                                                                        \
            value = xmalloc(sizeof *value);                             \
            *value = initial_value;                                     \
            xpthread_setspecific(NAME##_key, value);                    \
        }                                                               \
        return value;                                                   \
    }
#endif

/* DEFINE_PER_THREAD_MALLOCED_DATA(TYPE, NAME).
 *
 * This is a simple wrapper around POSIX per-thread data primitives.  It
 * defines per-thread variable NAME with the given TYPE, which must be a
 * pointer type.  In each thread, the per-thread variable is initialized to
 * NULL.  When a thread terminates, the variable is freed with free().
 *
 * The public interface to the variable is:
 *
 *    TYPE NAME_get(void)
 *    TYPE NAME_get_unsafe(void)
 *
 *       Returns the value of per-thread variable NAME in this thread.
 *
 *       Use NAME_get() in a context where this might be the first use of the
 *       per-thread variable in the program.  Use NAME_get_unsafe(), which
 *       avoids a conditional test and is thus slightly faster, in a context
 *       where one knows that NAME_get() has already been called previously.
 *
 *    TYPE NAME_set(TYPE new_value)
 *    TYPE NAME_set_unsafe(TYPE new_value)
 *
 *       Sets the value of per-thread variable NAME to 'new_value' in this
 *       thread, and returns its previous value.
 *
 *       Use NAME_set() in a context where this might be the first use of the
 *       per-thread variable in the program.  Use NAME_set_unsafe(), which
 *       avoids a conditional test and is thus slightly faster, in a context
 *       where one knows that NAME_set() has already been called previously.
 */
#define DEFINE_PER_THREAD_MALLOCED_DATA(TYPE, NAME)     \
    static pthread_key_t NAME##_key;                    \
                                                        \
    static void                                         \
    NAME##_once_init(void)                              \
    {                                                   \
        if (pthread_key_create(&NAME##_key, free)) {    \
            abort();                                    \
        }                                               \
    }                                                   \
                                                        \
    static void                                         \
    NAME##_init(void)                                   \
    {                                                   \
        static pthread_once_t once = PTHREAD_ONCE_INIT; \
        pthread_once(&once, NAME##_once_init);          \
    }                                                   \
                                                        \
    static TYPE                                         \
    NAME##_get_unsafe(void)                             \
    {                                                   \
        return pthread_getspecific(NAME##_key);         \
    }                                                   \
                                                        \
    static OVS_UNUSED TYPE                              \
    NAME##_get(void)                                    \
    {                                                   \
        NAME##_init();                                  \
        return NAME##_get_unsafe();                     \
    }                                                   \
                                                        \
    static TYPE                                         \
    NAME##_set_unsafe(TYPE value)                       \
    {                                                   \
        TYPE old_value = NAME##_get_unsafe();           \
        xpthread_setspecific(NAME##_key, value);        \
        return old_value;                               \
    }                                                   \
                                                        \
    static OVS_UNUSED TYPE                              \
    NAME##_set(TYPE value)                              \
    {                                                   \
        NAME##_init();                                  \
        return NAME##_set_unsafe(value);                \
    }
\f
/* 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 {
    atomic_bool done;
    struct ovs_mutex mutex;
};

#define OVSTHREAD_ONCE_INITIALIZER              \
    {                                           \
        ATOMIC_VAR_INIT(false),                 \
        OVS_ADAPTIVE_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(false, &once->mutex);

static inline bool
ovsthread_once_is_done__(const struct ovsthread_once *once)
{
    bool done;

    atomic_read_explicit(&once->done, &done, memory_order_relaxed);
    return done;
}

/* 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)
{
    return OVS_UNLIKELY(!ovsthread_once_is_done__(once)
                        && !ovsthread_once_start__(once));
}

#ifdef __CHECKER__
#define ovsthread_once_start(ONCE) \
    ((ONCE)->done ? false : ({ OVS_MACRO_LOCK((&ONCE->mutex)); true; }))
#endif
\f
/* Thread ID.
 *
 * pthread_t isn't so nice for some purposes.  Its size and representation are
 * implementation dependent, which means that there is no way to hash it.
 * This thread ID avoids the problem.
 */

DECLARE_EXTERN_PER_THREAD_DATA(unsigned int, ovsthread_id);

/* Returns a per-thread identifier unique within the lifetime of the
 * process. */
static inline unsigned int
ovsthread_id_self(void)
{
    return *ovsthread_id_get();
}
\f
void assert_single_threaded_at(const char *where);
#define assert_single_threaded() assert_single_threaded_at(SOURCE_LOCATOR)

pid_t xfork_at(const char *where);
#define xfork() xfork_at(SOURCE_LOCATOR)

void forbid_forking(const char *reason);
bool may_fork(void);

#endif /* ovs-thread.h */
Commit	Line	Data
ec68790f BP	1	/*
	2	* Copyright (c) 2013 Nicira, Inc.
	3	*
	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:
	7	*
	8	* http://www.apache.org/licenses/LICENSE-2.0
	9	*
	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.
	15	*/
	16
	17	#ifndef OVS_THREAD_H
	18	#define OVS_THREAD_H 1
	19
	20	#include <pthread.h>
728a8b14 BP	21	#include <stddef.h>
728a8b14 BP	22	#include <sys/types.h>
1514b275	23	#include "ovs-atomic.h"
ec68790f BP	24	#include "util.h"
ec68790f BP	25
97be1538 EJ	26
	27	/* Mutex. */
	28	struct OVS_LOCKABLE ovs_mutex {
	29	pthread_mutex_t lock;
	30	const char *where;
	31	};
	32
	33	/* "struct ovs_mutex" initializers:
ec68790f	34	*
97be1538	35	* - OVS_MUTEX_INITIALIZER: common case.
ec68790f	36	*
97be1538 EJ	37	* - OVS_ADAPTIVE_MUTEX_INITIALIZER for a mutex that spins briefly then goes
97be1538 EJ	38	* to sleeps after some number of iterations.
ec68790f	39	*
97be1538 EJ	40	* - OVS_ERRORCHECK_MUTEX_INITIALIZER for a mutex that is used for
	41	* error-checking. */
	42	#define OVS_MUTEX_INITIALIZER { PTHREAD_MUTEX_INITIALIZER, NULL }
ec68790f	43	#ifdef PTHREAD_ADAPTIVE_MUTEX_INITIALIZER_NP
97be1538 EJ	44	#define OVS_ADAPTIVE_MUTEX_INITIALIZER \
97be1538 EJ	45	{ PTHREAD_ADAPTIVE_MUTEX_INITIALIZER_NP, NULL }
ec68790f	46	#else
97be1538	47	#define OVS_ADAPTIVE_MUTEX_INITIALIZER OVS_MUTEX_INITIALIZER
ec68790f	48	#endif
ec68790f	49	#ifdef PTHREAD_ERRORCHECK_MUTEX_INITIALIZER_NP
97be1538 EJ	50	#define OVS_ERRORCHECK_MUTEX_INITIALIZER \
97be1538 EJ	51	{ PTHREAD_ERRORCHECK_MUTEX_INITIALIZER_NP, NULL }
ec68790f	52	#else
97be1538	53	#define OVS_ERRORCHECK_MUTEX_INITIALIZER OVS_MUTEX_INITIALIZER
ec68790f BP	54	#endif
ec68790f BP	55	\f
97be1538 EJ	56	/* Mutex types, suitable for use with pthread_mutexattr_settype().
	57	* There is only one nonstandard type:
	58	*
	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
	63	#else
	64	#define OVS_MUTEX_ADAPTIVE PTHREAD_MUTEX_NORMAL
	65	#endif
	66
	67	/* ovs_mutex functions analogous to pthread_mutex_*() functions.
	68	*
	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)
	76	OVS_ACQUIRES(mutex);
	77	#define ovs_mutex_lock(mutex) \
	78	ovs_mutex_lock_at(mutex, SOURCE_LOCATOR)
b847adc6	79
97be1538 EJ	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)
ec68790f	84
97be1538 EJ	85	void ovs_mutex_cond_wait(pthread_cond_t , const struct ovs_mutex );
97be1538 EJ	86
13d94ee9 AW	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);
	91
97be1538	92	/* Wrappers for pthread_mutexattr_() that abort the process on any error. /
b847adc6 BP	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);
	97
97be1538 EJ	98	/* Read-write lock. */
	99	struct OVS_LOCKABLE ovs_rwlock {
	100	pthread_rwlock_t lock;
	101	const char *where;
	102	};
	103
	104	/* Initializer. */
	105	#define OVS_RWLOCK_INITIALIZER { PTHREAD_RWLOCK_INITIALIZER, NULL }
	106
	107	/* ovs_rwlock functions analogous to pthread_rwlock_*() functions.
	108	*
	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);
	115
	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);
ec68790f	120
97be1538 EJ	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)
	125
	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);
	130
	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)
	135
	136	/* Wrappers for xpthread_cond_*() that abort the process on any error.
	137	*
	138	* Use ovs_mutex_cond_wait() to wait for a condition. */
ec68790f	139	void xpthread_cond_init(pthread_cond_t , pthread_condattr_t );
a8e736a8	140	void xpthread_cond_destroy(pthread_cond_t *);
ec68790f BP	141	void xpthread_cond_signal(pthread_cond_t *);
ec68790f BP	142	void xpthread_cond_broadcast(pthread_cond_t *);
ec68790f BP	143
	144	#ifdef __CHECKER__
	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
	153	#endif
	154
	155	void xpthread_key_create(pthread_key_t , void (destructor)(void *));
9c4c45ed	156	void xpthread_setspecific(pthread_key_t, const void *);
ec68790f BP	157
ec68790f BP	158	void xpthread_create(pthread_t , pthread_attr_t , void ()(void ), void );
c22095a5 BP	159	\f
	160	/* Per-thread data.
	161	*
	162	* Multiple forms of per-thread data exist, each with its own pluses and
	163	* minuses:
	164	*
	165	* - POSIX per-thread data via pthread_key_t is portable to any pthreads
	166	* implementation, and allows a destructor function to be defined. It
	167	* only (directly) supports per-thread pointers, which are always
	168	* initialized to NULL. It requires once-only allocation of a
	169	* pthread_key_t value. It is relatively slow.
	170	*
	171	* - The thread_local feature newly defined in C11 <threads.h> works with
	172	* any data type and initializer, and it is fast. thread_local does not
	173	* require once-only initialization like pthread_key_t. C11 does not
	174	* define what happens if one attempts to access a thread_local object
	175	* from a thread other than the one to which that object belongs. There
	176	* is no provision to call a user-specified destructor when a thread
	177	* ends.
	178	*
	179	* - The __thread keyword is a GCC extension similar to thread_local but
	180	* with a longer history. __thread is not portable to every GCC version
	181	* or environment. __thread does not restrict the use of a thread-local
	182	* object outside its own thread.
	183	*
	184	* Here's a handy summary:
	185	*
	186	* pthread_key_t thread_local __thread
	187	* ------------- ------------ -------------
	188	* portability high low medium
	189	* speed low high high
	190	* supports destructors? yes no no
	191	* needs key allocation? yes no no
	192	* arbitrary initializer? no yes yes
	193	* cross-thread access? yes no yes
	194	*/
	195
2ba4f163 BP	196	/* For static data, use this macro in a source file:
	197	*
	198	* DEFINE_STATIC_PER_THREAD_DATA(TYPE, NAME, INITIALIZER).
	199	*
	200	* For global data, "declare" the data in the header and "define" it in
	201	* the source file, with:
	202	*
	203	* DECLARE_EXTERN_PER_THREAD_DATA(TYPE, NAME).
	204	* DEFINE_EXTERN_PER_THREAD_DATA(NAME, INITIALIZER).
c22095a5 BP	205	*
	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.
	211	*
	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
	214	* static lifetime).
	215	*
	216	* The public interface to the variable is:
	217	*
	218	* TYPE *NAME_get(void)
	219	* TYPE *NAME_get_unsafe(void)
	220	*
	221	* Returns the address of this thread's instance of NAME.
	222	*
	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.
	227	*
	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.
	231	*/
	232	#if HAVE_THREAD_LOCAL \|\| HAVE___THREAD
	233
	234	#if HAVE_THREAD_LOCAL
	235	#include <threads.h>
	236	#elif HAVE___THREAD
	237	#define thread_local __thread
	238	#else
	239	#error
	240	#endif
	241
2ba4f163 BP	242	#define DEFINE_STATIC_PER_THREAD_DATA(TYPE, NAME, ...) \
	243	typedef TYPE NAME##_type; \
	244	\
	245	static NAME##_type * \
	246	NAME##_get_unsafe(void) \
	247	{ \
	248	static thread_local NAME##_type var = __VA_ARGS__; \
	249	return &var; \
	250	} \
	251	\
	252	static NAME##_type * \
	253	NAME##_get(void) \
	254	{ \
	255	return NAME##_get_unsafe(); \
c22095a5	256	}
2ba4f163 BP	257	#define DECLARE_EXTERN_PER_THREAD_DATA(TYPE, NAME) \
	258	typedef TYPE NAME##_type; \
	259	extern thread_local NAME##_type NAME##_var; \
	260	\
	261	static inline NAME##_type * \
	262	NAME##_get_unsafe(void) \
	263	{ \
	264	return &NAME##_var; \
	265	} \
	266	\
	267	static inline NAME##_type * \
	268	NAME##_get(void) \
	269	{ \
	270	return NAME##_get_unsafe(); \
	271	}
	272	#define DEFINE_EXTERN_PER_THREAD_DATA(NAME, ...) \
	273	thread_local NAME##_type NAME##_var = __VA_ARGS__;
c22095a5	274	#else /* no C implementation support for thread-local storage */
2ba4f163	275	#define DEFINE_STATIC_PER_THREAD_DATA(TYPE, NAME, ...) \
c22095a5 BP	276	typedef TYPE NAME##_type; \
	277	static pthread_key_t NAME##_key; \
	278	\
	279	static NAME##_type * \
	280	NAME##_get_unsafe(void) \
	281	{ \
	282	return pthread_getspecific(NAME##_key); \
	283	} \
	284	\
	285	static void \
	286	NAME##_once_init(void) \
	287	{ \
	288	if (pthread_key_create(&NAME##_key, free)) { \
	289	abort(); \
	290	} \
	291	} \
	292	\
	293	static NAME##_type * \
	294	NAME##_get(void) \
2ba4f163 BP	295	{ \
	296	static pthread_once_t once = PTHREAD_ONCE_INIT; \
	297	NAME##_type *value; \
	298	\
	299	pthread_once(&once, NAME##_once_init); \
	300	value = NAME##_get_unsafe(); \
	301	if (!value) { \
	302	static const NAME##_type initial_value = __VA_ARGS__; \
	303	\
	304	value = xmalloc(sizeof *value); \
	305	*value = initial_value; \
	306	xpthread_setspecific(NAME##_key, value); \
	307	} \
	308	return value; \
	309	}
	310	#define DECLARE_EXTERN_PER_THREAD_DATA(TYPE, NAME) \
	311	typedef TYPE NAME##_type; \
	312	static pthread_key_t NAME##_key; \
	313	\
	314	static inline NAME##_type * \
	315	NAME##_get_unsafe(void) \
	316	{ \
	317	return pthread_getspecific(NAME##_key); \
	318	} \
	319	\
	320	NAME##_type *NAME##_get(void);
	321	#define DEFINE_EXTERN_PER_THREAD_DATA(NAME, ...) \
	322	static void \
	323	NAME##_once_init(void) \
	324	{ \
	325	if (pthread_key_create(&NAME##_key, free)) { \
	326	abort(); \
	327	} \
	328	} \
	329	\
	330	NAME##_type * \
	331	NAME##_get(void) \
c22095a5 BP	332	{ \
	333	static pthread_once_t once = PTHREAD_ONCE_INIT; \
	334	NAME##_type *value; \
	335	\
	336	pthread_once(&once, NAME##_once_init); \
	337	value = NAME##_get_unsafe(); \
	338	if (!value) { \
	339	static const NAME##_type initial_value = __VA_ARGS__; \
	340	\
	341	value = xmalloc(sizeof *value); \
	342	*value = initial_value; \
9c4c45ed	343	xpthread_setspecific(NAME##_key, value); \
c22095a5 BP	344	} \
	345	return value; \
	346	}
	347	#endif
	348
	349	/* DEFINE_PER_THREAD_MALLOCED_DATA(TYPE, NAME).
	350	*
	351	* This is a simple wrapper around POSIX per-thread data primitives. It
	352	* defines per-thread variable NAME with the given TYPE, which must be a
	353	* pointer type. In each thread, the per-thread variable is initialized to
	354	* NULL. When a thread terminates, the variable is freed with free().
	355	*
	356	* The public interface to the variable is:
	357	*
	358	* TYPE NAME_get(void)
	359	* TYPE NAME_get_unsafe(void)
	360	*
	361	* Returns the value of per-thread variable NAME in this thread.
	362	*
	363	* Use NAME_get() in a context where this might be the first use of the
	364	* per-thread variable in the program. Use NAME_get_unsafe(), which
	365	* avoids a conditional test and is thus slightly faster, in a context
	366	* where one knows that NAME_get() has already been called previously.
	367	*
	368	* TYPE NAME_set(TYPE new_value)
	369	* TYPE NAME_set_unsafe(TYPE new_value)
	370	*
	371	* Sets the value of per-thread variable NAME to 'new_value' in this
	372	* thread, and returns its previous value.
	373	*
	374	* Use NAME_set() in a context where this might be the first use of the
	375	* per-thread variable in the program. Use NAME_set_unsafe(), which
	376	* avoids a conditional test and is thus slightly faster, in a context
	377	* where one knows that NAME_set() has already been called previously.
	378	*/
	379	#define DEFINE_PER_THREAD_MALLOCED_DATA(TYPE, NAME) \
	380	static pthread_key_t NAME##_key; \
	381	\
	382	static void \
	383	NAME##_once_init(void) \
	384	{ \
	385	if (pthread_key_create(&NAME##_key, free)) { \
	386	abort(); \
	387	} \
	388	} \
	389	\
	390	static void \
	391	NAME##_init(void) \
	392	{ \
	393	static pthread_once_t once = PTHREAD_ONCE_INIT; \
	394	pthread_once(&once, NAME##_once_init); \
	395	} \
	396	\
	397	static TYPE \
	398	NAME##_get_unsafe(void) \
	399	{ \
	400	return pthread_getspecific(NAME##_key); \
	401	} \
	402	\
	403	static OVS_UNUSED TYPE \
	404	NAME##_get(void) \
	405	{ \
	406	NAME##_init(); \
	407	return NAME##_get_unsafe(); \
408	} \
409	\
410	static TYPE \
411	NAME##_set_unsafe(TYPE value) \
412	{ \
413	TYPE old_value = NAME##_get_unsafe(); \
9c4c45ed	414	xpthread_setspecific(NAME##_key, value); \
c22095a5 BP	415	return old_value; \
	416	} \
	417	\
	418	static OVS_UNUSED TYPE \
	419	NAME##_set(TYPE value) \
	420	{ \
	421	NAME##_init(); \
	422	return NAME##_set_unsafe(value); \
	423	}
	424	\f
1514b275 BP	425	/* Convenient once-only execution.
	426	*
	427	*
	428	* Problem
	429	* =======
	430	*
	431	* POSIX provides pthread_once_t and pthread_once() as primitives for running a
	432	* set of code only once per process execution. They are used like this:
	433	*
	434	* static void run_once(void) { ...initialization... }
	435	* static pthread_once_t once = PTHREAD_ONCE_INIT;
	436	* ...
	437	* pthread_once(&once, run_once);
	438	*
	439	* pthread_once() does not allow passing any parameters to the initialization
	440	* function, which is often inconvenient, because it means that the function
	441	* can only access data declared at file scope.
	442	*
	443	*
	444	* Solution
	445	* ========
	446	*
	447	* Use ovsthread_once, like this, instead:
	448	*
	449	* static struct ovsthread_once once = OVSTHREAD_ONCE_INITIALIZER;
	450	*
	451	* if (ovsthread_once_start(&once)) {
	452	* ...initialization...
	453	* ovsthread_once_done(&once);
	454	* }
	455	*/
	456
	457	struct ovsthread_once {
	458	atomic_bool done;
97be1538	459	struct ovs_mutex mutex;
1514b275 BP	460	};
	461
	462	#define OVSTHREAD_ONCE_INITIALIZER \
	463	{ \
	464	ATOMIC_VAR_INIT(false), \
97be1538	465	OVS_ADAPTIVE_MUTEX_INITIALIZER, \
1514b275 BP	466	}
1514b275 BP	467
97be1538 EJ	468	static inline bool ovsthread_once_start(struct ovsthread_once *once)
	469	OVS_TRY_LOCK(true, &once->mutex);
	470	void ovsthread_once_done(struct ovsthread_once *once)
	471	OVS_RELEASES(&once->mutex);
1514b275	472
97be1538 EJ	473	bool ovsthread_once_start__(struct ovsthread_once *once)
97be1538 EJ	474	OVS_TRY_LOCK(false, &once->mutex);
1514b275 BP	475
	476	static inline bool
	477	ovsthread_once_is_done__(const struct ovsthread_once *once)
	478	{
	479	bool done;
	480
	481	atomic_read_explicit(&once->done, &done, memory_order_relaxed);
	482	return done;
	483	}
	484
	485	/* Returns true if this is the first call to ovsthread_once_start() for
	486	* 'once'. In this case, the caller should perform whatever initialization
	487	* actions it needs to do, then call ovsthread_once_done() for 'once'.
	488	*
	489	* Returns false if this is not the first call to ovsthread_once_start() for
	490	* 'once'. In this case, the call will not return until after
	491	* ovsthread_once_done() has been called. */
	492	static inline bool
	493	ovsthread_once_start(struct ovsthread_once *once)
	494	{
	495	return OVS_UNLIKELY(!ovsthread_once_is_done__(once)
	496	&& !ovsthread_once_start__(once));
	497	}
	498
	499	#ifdef __CHECKER__
	500	#define ovsthread_once_start(ONCE) \
97be1538	501	((ONCE)->done ? false : ({ OVS_MACRO_LOCK((&ONCE->mutex)); true; }))
1514b275	502	#endif
728a8b14	503	\f
6878fada BP	504	/* Thread ID.
	505	*
	506	* pthread_t isn't so nice for some purposes. Its size and representation are
	507	* implementation dependent, which means that there is no way to hash it.
	508	* This thread ID avoids the problem.
	509	*/
	510
	511	DECLARE_EXTERN_PER_THREAD_DATA(unsigned int, ovsthread_id);
	512
	513	/* Returns a per-thread identifier unique within the lifetime of the
	514	* process. */
	515	static inline unsigned int
	516	ovsthread_id_self(void)
	517	{
	518	return *ovsthread_id_get();
	519	}
	520	\f
5453ae20 BP	521	void assert_single_threaded_at(const char *where);
5453ae20 BP	522	#define assert_single_threaded() assert_single_threaded_at(SOURCE_LOCATOR)
728a8b14	523
5453ae20 BP	524	pid_t xfork_at(const char *where);
5453ae20 BP	525	#define xfork() xfork_at(SOURCE_LOCATOR)
728a8b14 BP	526
	527	void forbid_forking(const char *reason);
	528	bool may_fork(void);
ec68790f BP	529
ec68790f BP	530	#endif /* ovs-thread.h */