diff options
Diffstat (limited to 'tsd.c')
| -rw-r--r-- | tsd.c | 436 |
1 files changed, 270 insertions, 166 deletions
@@ -5,202 +5,306 @@ * POSIX thread functions which implement thread-specific data (TSD). */ -/* - * Why we can't use Win32 TLS - * -------------------------- - * - * In a word: Destructors - * - * POSIX 1003.1 1996, Section 17 allows for optional destructor functions - * to be associated with each key value. - * - * This is my (revised) understanding of how destructors work: - * - * A key is created by a single thread, which then provides in every - * existing thread a TSD matching the same key, but initialised - * to NULL. Each new thread will also get a matching key with value NULL. - * The creating thread can optionally associate a function, called a - * destructor, with the key. - * - * When each thread exits, it calls the destructor function, which - * will then perform an action on that threads key value - * only. (Previously I thought that only the key creating thread ran - * the destructor on the key in all threads. That proposition is - * sounding scarier by the minute.) - * - * SOME APPROACHES TO MANAGING TSD MEMORY - * - * We could simply allocate enough memory on process startup to hold - * all possible data for all possible threads. - * - * We could allocate memory for just a table to hold a single pointer - * for each of POSIX_THREAD_KEYS_MAX keys. pthread_key_create() could then - * allocate space for POSIX_THREADS_MAX key values in one hit and store - * the location of the array in the first table. - * - * The standard also suggests that each thread might store key/value pairs - * on its private stack. This seems like a good idea. I had concerns about - * memory leaks and key re-use if a key was deleted, but the standard talks - * at length on this and basically says it's up to the application to - * make sure everything goes smoothly here, making sure that proper cleanup - * is done before a key is deleted. (section B.17.1.3 in particular) - * - * One more thing to note: destructors must never be called on deleted keys. - */ - -#include <errno.h> - #include "pthread.h" #include "implement.h" +/* + * Code contributed by John E. Bossom <JEB>. + */ + int -pthread_key_create(pthread_key_t *key, void (*destructor)(void *)) +pthread_key_create (pthread_key_t * key, void (*destructor) (void *)) + /* + * ------------------------------------------------------ + * DOCPUBLIC + * This function creates a thread-specific data key visible + * to all threads. All existing and new threads have a value + * NULL for key until set using pthread_setspecific. When any + * thread with a non-NULL value for key terminates, 'destructor' + * is called with key's current value for that thread. + * + * PARAMETERS + * key + * pointer to an instance of pthread_key_t + * + * + * DESCRIPTION + * This function creates a thread-specific data key visible + * to all threads. All existing and new threads have a value + * NULL for key until set using pthread_setspecific. When any + * thread with a non-NULL value for key terminates, 'destructor' + * is called with key's current value for that thread. + * + * RESULTS + * 0 successfully created semaphore, + * EAGAIN insufficient resources or PTHREAD_KEYS_MAX + * exceeded, + * ENOMEM insufficient memory to create the key, + * + * ------------------------------------------------------ + */ { - pthread_key_t k; - int ret = 0; - - /* CRITICAL SECTION */ - pthread_mutex_lock(&_pthread_tsd_mutex); - - if (_pthread_key_reuse_top >= 0) + int result = 0; + + if ((*key = (pthread_key_t) calloc (1, sizeof (**key))) == NULL) { - k = _pthread_key_reuse[_pthread_key_reuse_top--]; + result = ENOMEM; } - else + else if (((*key)->key = TlsAlloc ()) == TLS_OUT_OF_INDEXES) { - if (_pthread_key_virgin_next < PTHREAD_KEYS_MAX) - { - k = _pthread_key_virgins[_pthread_key_virgin_next++]; - } - else - { - return EAGAIN; - } - } - - /* FIXME: This needs to be implemented as a list plus a re-use stack as for - thread IDs. _pthread_destructor_run_all() then needs to be changed - to push keys onto the re-use stack. - */ - - _pthread_tsd_key_table[k].in_use = 0; - _pthread_tsd_key_table[k].status = _PTHREAD_TSD_KEY_INUSE; - _pthread_tsd_key_table[k].destructor = destructor; - - pthread_mutex_unlock(&_pthread_tsd_mutex); - /* END CRITICAL SECTION */ - - *key = k; - - return ret; -} - -int -pthread_setspecific(pthread_key_t key, void *value) -{ - void ** keys; - int inuse; - - /* CRITICAL SECTION */ - pthread_mutex_lock(&_pthread_tsd_mutex); - - inuse = (_pthread_tsd_key_table[key].status == _PTHREAD_TSD_KEY_INUSE); - - pthread_mutex_unlock(&_pthread_tsd_mutex); - /* END CRITICAL SECTION */ - - if (! inuse) - return EINVAL; - - keys = (void **) TlsGetValue(_pthread_TSD_keys_TlsIndex); + /* + * Create system key + */ + result = EAGAIN; - if (keys[key] != NULL) - { - if (value == NULL) - { - /* Key is no longer in use by this thread. */ - _pthread_tsd_key_table[key].in_use--; - } + free (*key); + *key = NULL; } - else + else if (destructor != NULL) { - if (value != NULL) - { - /* Key is now in use by this thread. */ - _pthread_tsd_key_table[key].in_use++; - } + /* + * Have to manage associations between thread and key; + * Therefore, need a lock that allows multiple threads + * to gain exclusive access to the key->threads list + */ + result = pthread_mutex_init (&((*key)->threadsLock), NULL); + + if (result != 0) + { + TlsFree ((*key)->key); + + free (*key); + *key = NULL; + } + (*key)->destructor = destructor; } - keys[key] = value; - - return 0; + return (result); } -void * -pthread_getspecific(pthread_key_t key) +int +pthread_key_delete (pthread_key_t key) + /* + * ------------------------------------------------------ + * DOCPUBLIC + * This function deletes a thread-specific data key. This + * does not change the value of the thread spcific data key + * for any thread and does not run the key's destructor + * in any thread so it should be used with caution. + * + * PARAMETERS + * key + * pointer to an instance of pthread_key_t + * + * + * DESCRIPTION + * This function deletes a thread-specific data key. This + * does not change the value of the thread spcific data key + * for any thread and does not run the key's destructor + * in any thread so it should be used with caution. + * + * RESULTS + * 0 successfully deleted the key, + * EINVAL key is invalid, + * + * ------------------------------------------------------ + */ { - void ** keys; - int inuse; - - /* CRITICAL SECTION */ - pthread_mutex_lock(&_pthread_tsd_mutex); - - inuse = (_pthread_tsd_key_table[key].status == _PTHREAD_TSD_KEY_INUSE); + int result = 0; - pthread_mutex_unlock(&_pthread_tsd_mutex); - /* END CRITICAL SECTION */ - - if (! inuse) - return (void *) NULL; + if (key != NULL) + { + if (key->threads != NULL && + pthread_mutex_lock (&(key->threadsLock)) == 0) + { + /* + * Run through all Thread<-->Key associations + * for this key. + * If the pthread_t still exits (ie the assoc->thread + * is not NULL) then leave the assoc for the thread to + * destroy. + * Notes: + * If assoc->thread is NULL, then the associated thread + * is no longer referencing this assoc. + * The association is only referenced + * by this key and must be released; otherwise + * the assoc will be destroyed when the thread is destroyed. + */ + ThreadKeyAssoc *assoc; + + assoc = (ThreadKeyAssoc *) key->threads; + + while (assoc != NULL) + { + if (pthread_mutex_lock (&(assoc->lock)) == 0) + { + ThreadKeyAssoc *next; + + assoc->key = NULL; + next = assoc->nextThread; + assoc->nextThread = NULL; + + pthread_mutex_unlock (&(assoc->lock)); + + _pthread_tkAssocDestroy (assoc); + + assoc = next; + } + } + pthread_mutex_unlock (&(key->threadsLock)); + } + + TlsFree (key->key); + if (key->destructor != NULL) + { + pthread_mutex_destroy (&(key->threadsLock)); + } + +#if defined( _DEBUG ) + memset ((char *) key, 0, sizeof (*key)); +#endif + free (key); + } - keys = (void **) TlsGetValue(_pthread_TSD_keys_TlsIndex); - return keys[key]; + return (result); } -/* - pthread_key_delete: - - ANSI/IEEE Std 1003.1, 1996 Edition - - Section 17.1.3.2 - - This function deletes a thread-specific data key previously returned by - pthread_key_create(). The thread specific data values associated with - "key" need not be NULL at the time pthread_key_delete() is called. It is - the responsibility of the application to free any application storage - or perform any cleanup actions for data structures related to the deleted - key or associated thread-specific data in any threads; this cleanup - can be done either before or after pthread_key_delete() is called. Any - attempt to use "key" following the call to pthread_key_delete() - results in undefined behaviour. - - The pthread_key_delete() function shall be callable from within - destructor functions. No destructor functions shall be invoked by - pthread_key_delete(). Any destructor function that may have been associated - with "key" shall no longer be called upon thread exit. - */ int -pthread_key_delete(pthread_key_t key) +pthread_setspecific (pthread_key_t key, const void *value) + /* + * ------------------------------------------------------ + * DOCPUBLIC + * This function initializes an unnamed semaphore. the + * initial value of the semaphore is 'value' + * + * PARAMETERS + * sem + * pointer to an instance of sem_t + * + * + * DESCRIPTION + * This function initializes an unnamed semaphore. The + * initial value of the semaphore is set to 'value'. + * + * RESULTS + * 0 successfully created semaphore, + * EINVAL 'sem' is not a valid semaphore, + * ENOSPC a required resource has been exhausted, + * ENOSYS semaphores are not supported, + * EPERM the process lacks appropriate privilege + * + * ------------------------------------------------------ + */ { - int ret = 0; - - /* CRITICAL SECTION */ - pthread_mutex_lock(&_pthread_tsd_mutex); + pthread_t self; + int result = 0; - if (_pthread_tsd_key_table[key].status != _PTHREAD_TSD_KEY_INUSE) + if (key != _pthread_selfThreadKey) { - ret = EINVAL; + /* + * Using pthread_self will implicitly create + * an instance of pthread_t for the current + * thread if one wasn't explicitly created + */ + self = pthread_self (); } else { - _pthread_tsd_key_table[key].status = _PTHREAD_TSD_KEY_DELETED; - _pthread_tsd_key_table[key].destructor = NULL; + /* + * Resolve catch-22 of registering thread with threadSelf + * key + */ + self = pthread_getspecific (_pthread_selfThreadKey); + if (self == NULL) + { + self = (pthread_t) value; + } + } + + result = 0; + + if (key != NULL) + { + ThreadKeyAssoc *assoc; + + if (self != NULL && + key->destructor != NULL && + value != NULL) + { + /* + * Only require associations if we have to + * call user destroy routine. + * Don't need to locate an existing association + * when setting data to NULL for WIN32 since the + * data is stored with the operating system; not + * on the association; setting assoc to NULL short + * circuits the search. + */ + assoc = (ThreadKeyAssoc *) self->keys; + /* + * Locate existing association + */ + while (assoc != NULL) + { + if (assoc->key == key) + { + /* + * Association already exists + */ + break; + } + assoc = assoc->nextKey; + } + + /* + * create an association if not found + */ + result = (assoc == NULL) + ? _pthread_tkAssocCreate (&assoc, self, key) + : 0; + } + else + { + result = 0; + } + + if (result == 0) + { + TlsSetValue (key->key, (LPVOID) value); + } } + return (result); +} /* pthread_setspecific */ - pthread_mutex_unlock(&_pthread_tsd_mutex); - /* END CRITICAL SECTION */ - return ret; +void * +pthread_getspecific (pthread_key_t key) + /* + * ------------------------------------------------------ + * DOCPUBLIC + * This function returns the current value of key in the + * calling thread. If no value has been set for 'key' in + * the thread, NULL is returned. + * + * PARAMETERS + * key + * an instance of pthread_key_t + * + * + * DESCRIPTION + * This function returns the current value of key in the + * calling thread. If no value has been set for 'key' in + * the thread, NULL is returned. + * + * RESULTS + * key value + * + * ------------------------------------------------------ + */ +{ + return (TlsGetValue (key->key)); } +/* </JEB> */ + |