/*
- * Copyright (c) 2013 Nicira, Inc.
+ * 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.
#include <stddef.h>
#include <sys/types.h>
#include "ovs-atomic.h"
+#include "openvswitch/thread.h"
#include "util.h"
-/* glibc has some non-portable mutex types and initializers:
- *
- * - PTHREAD_MUTEX_ADAPTIVE_NP is a mutex type that works as a spinlock that
- * falls back to a mutex after spinning for some number of iterations.
+struct seq;
+
+/* Poll-block()-able barrier similar to pthread_barrier_t. */
+struct ovs_barrier {
+ uint32_t size; /* Number of threads to wait. */
+ atomic_count count; /* Number of threads already hit the barrier. */
+ struct seq *seq;
+};
+
+/* 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.
*
- * - PTHREAD_ERRORCHECK_MUTEX_INITIALIZER_NP is a non-portable initializer
- * for an error-checking mutex.
+ * An ovs_rwlock does not support recursive readers, because POSIX allows
+ * taking the reader lock recursively to deadlock when a thread is waiting on
+ * the write-lock. (NetBSD does deadlock.) glibc rwlocks in their default
+ * configuration do not deadlock, but ovs_rwlock_init() initializes rwlocks as
+ * non-recursive (which will deadlock) for two reasons:
*
- * We use these definitions to fall back to PTHREAD_MUTEX_NORMAL instead in
- * these cases.
+ * - glibc only provides fairness to writers in this mode.
*
- * (glibc has other non-portable initializers, but we can't reasonably
- * substitute for them here.) */
-#ifdef PTHREAD_ADAPTIVE_MUTEX_INITIALIZER_NP
-#define PTHREAD_MUTEX_ADAPTIVE PTHREAD_MUTEX_ADAPTIVE_NP
-#define PTHREAD_ADAPTIVE_MUTEX_INITIALIZER \
- PTHREAD_ADAPTIVE_MUTEX_INITIALIZER_NP
+ * - It's better to find bugs in the primary Open vSwitch target rather
+ * than exposing them only to porters. */
+struct OVS_LOCKABLE ovs_rwlock {
+ pthread_rwlock_t lock;
+ const char *where; /* NULL if and only if uninitialized. */
+};
+
+/* Initializer. */
+#ifdef PTHREAD_RWLOCK_WRITER_NONRECURSIVE_INITIALIZER_NP
+#define OVS_RWLOCK_INITIALIZER \
+ { PTHREAD_RWLOCK_WRITER_NONRECURSIVE_INITIALIZER_NP, "<unlocked>" }
#else
-#define PTHREAD_MUTEX_ADAPTIVE PTHREAD_MUTEX_NORMAL
-#define PTHREAD_ADAPTIVE_MUTEX_INITIALIZER PTHREAD_MUTEX_INITIALIZER
+#define OVS_RWLOCK_INITIALIZER { PTHREAD_RWLOCK_INITIALIZER, "<unlocked>" }
#endif
-#ifdef PTHREAD_ERRORCHECK_MUTEX_INITIALIZER_NP
-#define PTHREAD_ERRORCHECK_MUTEX_INITIALIZER \
- PTHREAD_ERRORCHECK_MUTEX_INITIALIZER_NP
-#else
-#define PTHREAD_ERRORCHECK_MUTEX_INITIALIZER PTHREAD_MUTEX_INITIALIZER
+/* 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);
+
+/* Wrappers for pthread_rwlockattr_*() that abort the process on any error. */
+void xpthread_rwlockattr_init(pthread_rwlockattr_t *);
+void xpthread_rwlockattr_destroy(pthread_rwlockattr_t *);
+#ifdef PTHREAD_RWLOCK_WRITER_NONRECURSIVE_INITIALIZER_NP
+void xpthread_rwlockattr_setkind_np(pthread_rwlockattr_t *, int kind);
#endif
-\f
-/* Simple wrappers for pthreads functions. Most of these functions abort the
- * process with an error message on any error. The *_trylock() functions are
- * exceptions: they pass through a 0 or EBUSY return value to the caller and
- * abort on any other error. */
-void xpthread_mutex_init(pthread_mutex_t *, pthread_mutexattr_t *);
-void xpthread_mutex_destroy(pthread_mutex_t *);
-void xpthread_mutex_lock(pthread_mutex_t *mutex) OVS_ACQUIRES(mutex);
-void xpthread_mutex_unlock(pthread_mutex_t *mutex) OVS_RELEASES(mutex);
-int xpthread_mutex_trylock(pthread_mutex_t *);
+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, OVS_SOURCE_LOCATOR)
-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);
+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, OVS_SOURCE_LOCATOR)
-void xpthread_rwlock_init(pthread_rwlock_t *, pthread_rwlockattr_t *);
-void xpthread_rwlock_destroy(pthread_rwlock_t *);
-void xpthread_rwlock_rdlock(pthread_rwlock_t *rwlock) OVS_ACQUIRES(rwlock);
-void xpthread_rwlock_wrlock(pthread_rwlock_t *rwlock) OVS_ACQUIRES(rwlock);
-void xpthread_rwlock_unlock(pthread_rwlock_t *rwlock) OVS_RELEASES(rwlock);
-int xpthread_rwlock_tryrdlock(pthread_rwlock_t *);
-int xpthread_rwlock_trywrlock(pthread_rwlock_t *);
+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, OVS_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, OVS_SOURCE_LOCATOR)
+
+/* ovs_barrier functions analogous to pthread_barrier_*() functions. */
+void ovs_barrier_init(struct ovs_barrier *, uint32_t count);
+void ovs_barrier_destroy(struct ovs_barrier *);
+void ovs_barrier_block(struct ovs_barrier *);
+
+/* 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 *);
-void xpthread_cond_wait(pthread_cond_t *, pthread_mutex_t *mutex)
- OVS_MUST_HOLD(mutex);
-
-#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_key_delete(pthread_key_t);
+void xpthread_setspecific(pthread_key_t, const void *);
+
+#ifndef _WIN32
+void xpthread_sigmask(int, const sigset_t *, sigset_t *);
+#endif
-void xpthread_create(pthread_t *, pthread_attr_t *, void *(*)(void *), void *);
+pthread_t ovs_thread_create(const char *name, void *(*)(void *), void *);
+void xpthread_join(pthread_t, void **);
\f
/* Per-thread data.
*
- * Multiple forms of per-thread data exist, each with its own pluses and
- * minuses:
+ *
+ * Standard Forms
+ * ==============
+ *
+ * Multiple forms of standard per-thread data exist, each with its own pluses
+ * and minuses. In general, if one of these forms is appropriate, then it's a
+ * good idea to use it:
*
* - 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.
+ * pthread_key_t value. It is relatively slow. Typically few
+ * "pthread_key_t"s are available (POSIX requires only at least 128,
+ * glibc supplies only 1024).
*
* - 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
* 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.
+ * ends. Typical implementations allow for an arbitrary amount of
+ * thread_local storage, but statically allocated only.
*
* - The __thread keyword is a GCC extension similar to thread_local but
* with a longer history. __thread is not portable to every GCC version
* needs key allocation? yes no no
* arbitrary initializer? no yes yes
* cross-thread access? yes no yes
+ * amount available? few arbitrary arbitrary
+ * dynamically allocated? yes no no
+ *
+ *
+ * Extensions
+ * ==========
+ *
+ * OVS provides some extensions and wrappers:
+ *
+ * - In a situation where the performance of thread_local or __thread is
+ * desirable, but portability is required, DEFINE_STATIC_PER_THREAD_DATA
+ * and DECLARE_EXTERN_PER_THREAD_DATA/DEFINE_EXTERN_PER_THREAD_DATA may
+ * be appropriate (see below).
+ *
+ * - DEFINE_PER_THREAD_MALLOCED_DATA can be convenient for simple
+ * per-thread malloc()'d buffers.
+ *
+ * - struct ovs_tsd provides an alternative to pthread_key_t that isn't
+ * limited to a small number of keys.
*/
-/* DEFINE_PER_THREAD_DATA(TYPE, NAME, INITIALIZER).
+/* 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).
#error
#endif
-#define DEFINE_PER_THREAD_DATA(TYPE, NAME, ...) \
- typedef TYPE NAME##_type; \
- static thread_local NAME##_type NAME##_var = __VA_ARGS__; \
- \
- static NAME##_type * \
- NAME##_get_unsafe(void) \
- { \
- return &NAME##_var; \
- } \
- \
- static NAME##_type * \
- NAME##_get(void) \
- { \
- return NAME##_get_unsafe(); \
+#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_PER_THREAD_DATA(TYPE, NAME, ...) \
+#define DEFINE_STATIC_PER_THREAD_DATA(TYPE, NAME, ...) \
typedef TYPE NAME##_type; \
static pthread_key_t NAME##_key; \
\
if (!value) { \
static const NAME##_type initial_value = __VA_ARGS__; \
\
- value = xmalloc(sizeof *value); \
+ value = malloc(sizeof *value); \
+ if (value == NULL) { \
+ out_of_memory(); \
+ } \
*value = initial_value; \
- pthread_setspecific(NAME##_key, 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 = malloc(sizeof *value); \
+ if (value == NULL) { \
+ out_of_memory(); \
+ } \
+ *value = initial_value; \
+ xpthread_setspecific(NAME##_key, value); \
} \
return value; \
}
NAME##_set_unsafe(TYPE value) \
{ \
TYPE old_value = NAME##_get_unsafe(); \
- pthread_setspecific(NAME##_key, value); \
+ xpthread_setspecific(NAME##_key, value); \
return old_value; \
} \
\
NAME##_init(); \
return NAME##_set_unsafe(value); \
}
-\f
-/* Convenient once-only execution.
+
+/* Dynamically allocated thread-specific data with lots of slots.
*
+ * pthread_key_t can provide as few as 128 pieces of thread-specific data (even
+ * glibc is limited to 1,024). Thus, one must be careful to allocate only a
+ * few keys globally. One cannot, for example, allocate a key for every
+ * instance of a data structure if there might be an arbitrary number of those
+ * data structures.
*
- * Problem
- * =======
+ * This API is similar to the pthread one (simply search and replace pthread_
+ * by ovsthread_) but it a much larger limit that can be raised if necessary
+ * (by recompiling). Thus, one may more freely use this form of
+ * thread-specific data.
*
- * 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:
+ * ovsthread_key_t also differs from pthread_key_t in the following ways:
*
- * static void run_once(void) { ...initialization... }
- * static pthread_once_t once = PTHREAD_ONCE_INIT;
- * ...
- * pthread_once(&once, run_once);
+ * - Destructors must not access thread-specific data (via ovsthread_key).
*
- * 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.
+ * - The pthread_key_t API allows concurrently exiting threads to start
+ * executing the destructor after pthread_key_delete() returns. The
+ * ovsthread_key_t API guarantees that, when ovsthread_key_delete()
+ * returns, all destructors have returned and no new ones will start
+ * execution.
+ */
+typedef struct ovsthread_key *ovsthread_key_t;
+
+void ovsthread_key_create(ovsthread_key_t *, void (*destructor)(void *));
+void ovsthread_key_delete(ovsthread_key_t);
+
+void ovsthread_setspecific(ovsthread_key_t, const void *);
+void *ovsthread_getspecific(ovsthread_key_t);
+\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
+/* Simulated global counter.
*
- * Solution
- * ========
+ * Incrementing such a counter is meant to be cheaper than incrementing a
+ * global counter protected by a lock. It is probably more expensive than
+ * incrementing a truly thread-local variable, but such a variable has no
+ * straightforward way to get the sum.
*
- * Use ovsthread_once, like this, instead:
*
- * static struct ovsthread_once once = OVSTHREAD_ONCE_INITIALIZER;
+ * Thread-safety
+ * =============
*
- * if (ovsthread_once_start(&once)) {
- * ...initialization...
- * ovsthread_once_done(&once);
- * }
- */
+ * Fully thread-safe. */
-struct ovsthread_once {
- atomic_bool done;
- pthread_mutex_t mutex;
+struct ovsthread_stats {
+ struct ovs_mutex mutex;
+ void *volatile buckets[16];
};
-#define OVSTHREAD_ONCE_INITIALIZER \
- { \
- ATOMIC_VAR_INIT(false), \
- PTHREAD_ADAPTIVE_MUTEX_INITIALIZER, \
- }
-
-static inline bool ovsthread_once_start(struct ovsthread_once *);
-void ovsthread_once_done(struct ovsthread_once *once) OVS_RELEASES(once);
-
-bool ovsthread_once_start__(struct ovsthread_once *);
-
-static inline bool
-ovsthread_once_is_done__(const struct ovsthread_once *once)
-{
- bool done;
+void ovsthread_stats_init(struct ovsthread_stats *);
+void ovsthread_stats_destroy(struct ovsthread_stats *);
- 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));
-}
+void *ovsthread_stats_bucket_get(struct ovsthread_stats *,
+ void *(*new_bucket)(void));
-#ifdef __CHECKER__
-#define ovsthread_once_start(ONCE) \
- ((ONCE)->done ? false : ({ OVS_ACQUIRE(ONCE); true; }))
-#endif
+#define OVSTHREAD_STATS_FOR_EACH_BUCKET(BUCKET, IDX, STATS) \
+ for ((IDX) = ovs_thread_stats_next_bucket(STATS, 0); \
+ ((IDX) < ARRAY_SIZE((STATS)->buckets) \
+ ? ((BUCKET) = (STATS)->buckets[IDX], true) \
+ : false); \
+ (IDX) = ovs_thread_stats_next_bucket(STATS, (IDX) + 1))
+size_t ovs_thread_stats_next_bucket(const struct ovsthread_stats *, size_t);
\f
+bool single_threaded(void);
+
void assert_single_threaded_at(const char *where);
-#define assert_single_threaded() assert_single_threaded_at(SOURCE_LOCATOR)
+#define assert_single_threaded() assert_single_threaded_at(OVS_SOURCE_LOCATOR)
+#ifndef _WIN32
pid_t xfork_at(const char *where);
-#define xfork() xfork_at(SOURCE_LOCATOR)
+#define xfork() xfork_at(OVS_SOURCE_LOCATOR)
+#endif
void forbid_forking(const char *reason);
bool may_fork(void);
+\f
+/* Useful functions related to threading. */
+
+int count_cpu_cores(void);
+bool thread_is_pmd(void);
#endif /* ovs-thread.h */
projects / cascardo / ovs.git / blobdiff