X-Git-Url: http://git.onelab.eu/?a=blobdiff_plain;f=lib%2Fovs-thread.h;h=8cf2ecca3f217fd391ab77c03fdc68e54af14d5b;hb=fe29af4c888d48cc1f16b1a247c2ffb6f0864522;hp=c6a71426905172b1cd221d96155d1f10217cecd3;hpb=0122f6e65c5f92da210d3fc024b781cc4faa8a6f;p=sliver-openvswitch.git diff --git a/lib/ovs-thread.h b/lib/ovs-thread.h index c6a714269..8cf2ecca3 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. @@ -127,6 +127,7 @@ void xpthread_cond_broadcast(pthread_cond_t *); #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 +135,21 @@ 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 +157,8 @@ 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 +175,25 @@ 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: @@ -276,7 +304,10 @@ void xpthread_join(pthread_t, void **); 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; \ xpthread_setspecific(NAME##_key, value); \ } \ @@ -313,7 +344,10 @@ void xpthread_join(pthread_t, void **); 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; \ xpthread_setspecific(NAME##_key, value); \ } \ @@ -396,6 +430,31 @@ 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. + * + * Compared to pthread_key_t, ovsthread_key_t has the follow limitations: + * + * - Destructors must not access thread-specific data (via ovsthread_key). + */ +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. * @@ -488,6 +547,25 @@ 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) @@ -499,6 +577,6 @@ bool may_fork(void); /* Useful functions related to threading. */ -unsigned int count_cpu_cores(void); +int count_cpu_cores(void); #endif /* ovs-thread.h */