X-Git-Url: http://git.onelab.eu/?a=blobdiff_plain;f=lib%2Fovs-thread.h;h=2e9a937f585b9ca44182abd1c9e2ca64266441a6;hb=3ba9c6a5a5468626dcfeb1f9a750bb0efc8c6a7a;hp=b6d973f6e46beffd20f107970988d4eb5474ed24;hpb=4974b2b8119e8268eb7cababf82f2e7d84455f4a;p=sliver-openvswitch.git diff --git a/lib/ovs-thread.h b/lib/ovs-thread.h index b6d973f6e..2e9a937f5 100644 --- a/lib/ovs-thread.h +++ b/lib/ovs-thread.h @@ -1,5 +1,5 @@ /* - * 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. @@ -37,6 +37,13 @@ struct OVS_LOCKABLE ovs_mutex { #define OVS_MUTEX_INITIALIZER { PTHREAD_MUTEX_INITIALIZER, NULL } #endif +#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 + /* ovs_mutex functions analogous to pthread_mutex_*() functions. * * Most of these functions abort the process with an error message on any @@ -44,6 +51,7 @@ struct OVS_LOCKABLE ovs_mutex { * return value to the caller and aborts on any other error. */ void ovs_mutex_init(const struct ovs_mutex *); void ovs_mutex_init_recursive(const struct ovs_mutex *); +void ovs_mutex_init_adaptive(const struct ovs_mutex *); 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) @@ -69,14 +77,30 @@ 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. */ +/* Read-write lock. + * + * 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: + * + * - glibc only provides fairness to writers in this mode. + * + * - 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; }; /* Initializer. */ +#ifdef PTHREAD_RWLOCK_WRITER_NONRECURSIVE_INITIALIZER_NP +#define OVS_RWLOCK_INITIALIZER \ + { PTHREAD_RWLOCK_WRITER_NONRECURSIVE_INITIALIZER_NP, NULL } +#else #define OVS_RWLOCK_INITIALIZER { PTHREAD_RWLOCK_INITIALIZER, NULL } +#endif /* ovs_rwlock functions analogous to pthread_rwlock_*() functions. * @@ -87,6 +111,13 @@ 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 + void ovs_rwlock_wrlock_at(const struct ovs_rwlock *rwlock, const char *where) OVS_ACQ_WRLOCK(rwlock); #define ovs_rwlock_wrlock(rwlock) \ @@ -115,18 +146,8 @@ 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 - * 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 *); void xpthread_create(pthread_t *, pthread_attr_t *, void *(*)(void *), void *); @@ -134,14 +155,21 @@ void xpthread_join(pthread_t, void **); /* 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 works with * any data type and initializer, and it is fast. thread_local does not @@ -149,7 +177,8 @@ void xpthread_join(pthread_t, void **); * 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 @@ -166,6 +195,25 @@ void xpthread_join(pthread_t, void **); * 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. */ /* For static data, use this macro in a source file: @@ -402,6 +450,37 @@ void xpthread_join(pthread_t, void **); NAME##_init(); \ return NAME##_set_unsafe(value); \ } + +/* 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. + * + * 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. + * + * ovsthread_key_t also differs from pthread_key_t in the following ways: + * + * - Destructors must not access thread-specific data (via ovsthread_key). + * + * - 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); /* Convenient once-only execution. * @@ -494,6 +573,25 @@ ovsthread_id_self(void) return *ovsthread_id_get(); } +/* Simulated global counter. + * + * 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. + * + * + * Thread-safety + * ============= + * + * Fully thread-safe. */ + +struct ovsthread_counter *ovsthread_counter_create(void); +void ovsthread_counter_destroy(struct ovsthread_counter *); +void ovsthread_counter_inc(struct ovsthread_counter *, unsigned long long int); +unsigned long long int ovsthread_counter_read( + const struct ovsthread_counter *); + void assert_single_threaded_at(const char *where); #define assert_single_threaded() assert_single_threaded_at(SOURCE_LOCATOR)