diff options
Diffstat (limited to 'nsprpub/pr/src/threads/prrwlock.c')
| -rw-r--r-- | nsprpub/pr/src/threads/prrwlock.c | 483 |
1 files changed, 483 insertions, 0 deletions
diff --git a/nsprpub/pr/src/threads/prrwlock.c b/nsprpub/pr/src/threads/prrwlock.c new file mode 100644 index 0000000000..2e0f9ea4e8 --- /dev/null +++ b/nsprpub/pr/src/threads/prrwlock.c @@ -0,0 +1,483 @@ +/* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 2 -*- */ +/* This Source Code Form is subject to the terms of the Mozilla Public + * License, v. 2.0. If a copy of the MPL was not distributed with this + * file, You can obtain one at http://mozilla.org/MPL/2.0/. */ + +#include "primpl.h" + +#include <string.h> + +#if defined(HPUX) && defined(_PR_PTHREADS) && !defined(_PR_DCETHREADS) + +#include <pthread.h> +#define HAVE_UNIX98_RWLOCK +#define RWLOCK_T pthread_rwlock_t +#define RWLOCK_INIT(lock) pthread_rwlock_init(lock, NULL) +#define RWLOCK_DESTROY(lock) pthread_rwlock_destroy(lock) +#define RWLOCK_RDLOCK(lock) pthread_rwlock_rdlock(lock) +#define RWLOCK_WRLOCK(lock) pthread_rwlock_wrlock(lock) +#define RWLOCK_UNLOCK(lock) pthread_rwlock_unlock(lock) + +#elif defined(SOLARIS) && (defined(_PR_PTHREADS) \ + || defined(_PR_GLOBAL_THREADS_ONLY)) + +#include <synch.h> +#define HAVE_UI_RWLOCK +#define RWLOCK_T rwlock_t +#define RWLOCK_INIT(lock) rwlock_init(lock, USYNC_THREAD, NULL) +#define RWLOCK_DESTROY(lock) rwlock_destroy(lock) +#define RWLOCK_RDLOCK(lock) rw_rdlock(lock) +#define RWLOCK_WRLOCK(lock) rw_wrlock(lock) +#define RWLOCK_UNLOCK(lock) rw_unlock(lock) + +#endif + +/* + * Reader-writer lock + */ +struct PRRWLock { + char *rw_name; /* lock name */ + PRUint32 rw_rank; /* rank of the lock */ + +#if defined(HAVE_UNIX98_RWLOCK) || defined(HAVE_UI_RWLOCK) + RWLOCK_T rw_lock; +#else + PRLock *rw_lock; + PRInt32 rw_lock_cnt; /* == 0, if unlocked */ + /* == -1, if write-locked */ + /* > 0 , # of read locks */ + PRUint32 rw_reader_cnt; /* number of waiting readers */ + PRUint32 rw_writer_cnt; /* number of waiting writers */ + PRCondVar *rw_reader_waitq; /* cvar for readers */ + PRCondVar *rw_writer_waitq; /* cvar for writers */ +#ifdef DEBUG + PRThread *rw_owner; /* lock owner for write-lock */ +#endif +#endif +}; + +#ifdef DEBUG +#define _PR_RWLOCK_RANK_ORDER_DEBUG /* enable deadlock detection using + rank-order for locks + */ +#endif + +#ifdef _PR_RWLOCK_RANK_ORDER_DEBUG + +static PRUintn pr_thread_rwlock_key; /* TPD key for lock stack */ +static PRUintn pr_thread_rwlock_alloc_failed; + +#define _PR_RWLOCK_RANK_ORDER_LIMIT 10 + +typedef struct thread_rwlock_stack { + PRInt32 trs_index; /* top of stack */ + PRRWLock *trs_stack[_PR_RWLOCK_RANK_ORDER_LIMIT]; /* stack of lock + pointers */ + +} thread_rwlock_stack; + +static void _PR_SET_THREAD_RWLOCK_RANK(PRRWLock *rwlock); +static PRUint32 _PR_GET_THREAD_RWLOCK_RANK(void); +static void _PR_UNSET_THREAD_RWLOCK_RANK(PRRWLock *rwlock); +static void _PR_RELEASE_LOCK_STACK(void *lock_stack); + +#endif + +/* + * Reader/Writer Locks + */ + +/* + * PR_NewRWLock + * Create a reader-writer lock, with the given lock rank and lock name + * + */ + +PR_IMPLEMENT(PRRWLock *) +PR_NewRWLock(PRUint32 lock_rank, const char *lock_name) +{ + PRRWLock *rwlock; +#if defined(HAVE_UNIX98_RWLOCK) || defined(HAVE_UI_RWLOCK) + int err; +#endif + + if (!_pr_initialized) _PR_ImplicitInitialization(); + + rwlock = PR_NEWZAP(PRRWLock); + if (rwlock == NULL) + return NULL; + + rwlock->rw_rank = lock_rank; + if (lock_name != NULL) { + rwlock->rw_name = (char*) PR_Malloc(strlen(lock_name) + 1); + if (rwlock->rw_name == NULL) { + PR_DELETE(rwlock); + return(NULL); + } + strcpy(rwlock->rw_name, lock_name); + } else { + rwlock->rw_name = NULL; + } + +#if defined(HAVE_UNIX98_RWLOCK) || defined(HAVE_UI_RWLOCK) + err = RWLOCK_INIT(&rwlock->rw_lock); + if (err != 0) { + PR_SetError(PR_UNKNOWN_ERROR, err); + PR_Free(rwlock->rw_name); + PR_DELETE(rwlock); + return NULL; + } + return rwlock; +#else + rwlock->rw_lock = PR_NewLock(); + if (rwlock->rw_lock == NULL) { + goto failed; + } + rwlock->rw_reader_waitq = PR_NewCondVar(rwlock->rw_lock); + if (rwlock->rw_reader_waitq == NULL) { + goto failed; + } + rwlock->rw_writer_waitq = PR_NewCondVar(rwlock->rw_lock); + if (rwlock->rw_writer_waitq == NULL) { + goto failed; + } + rwlock->rw_reader_cnt = 0; + rwlock->rw_writer_cnt = 0; + rwlock->rw_lock_cnt = 0; + return rwlock; + +failed: + if (rwlock->rw_reader_waitq != NULL) { + PR_DestroyCondVar(rwlock->rw_reader_waitq); + } + if (rwlock->rw_lock != NULL) { + PR_DestroyLock(rwlock->rw_lock); + } + PR_Free(rwlock->rw_name); + PR_DELETE(rwlock); + return NULL; +#endif +} + +/* +** Destroy the given RWLock "lock". +*/ +PR_IMPLEMENT(void) +PR_DestroyRWLock(PRRWLock *rwlock) +{ +#if defined(HAVE_UNIX98_RWLOCK) || defined(HAVE_UI_RWLOCK) + int err; + err = RWLOCK_DESTROY(&rwlock->rw_lock); + PR_ASSERT(err == 0); +#else + PR_ASSERT(rwlock->rw_reader_cnt == 0); + PR_DestroyCondVar(rwlock->rw_reader_waitq); + PR_DestroyCondVar(rwlock->rw_writer_waitq); + PR_DestroyLock(rwlock->rw_lock); +#endif + if (rwlock->rw_name != NULL) + PR_Free(rwlock->rw_name); + PR_DELETE(rwlock); +} + +/* +** Read-lock the RWLock. +*/ +PR_IMPLEMENT(void) +PR_RWLock_Rlock(PRRWLock *rwlock) +{ +#if defined(HAVE_UNIX98_RWLOCK) || defined(HAVE_UI_RWLOCK) +int err; +#endif + +#ifdef _PR_RWLOCK_RANK_ORDER_DEBUG + /* + * assert that rank ordering is not violated; the rank of 'rwlock' should + * be equal to or greater than the highest rank of all the locks held by + * the thread. + */ + PR_ASSERT((rwlock->rw_rank == PR_RWLOCK_RANK_NONE) || + (rwlock->rw_rank >= _PR_GET_THREAD_RWLOCK_RANK())); +#endif + +#if defined(HAVE_UNIX98_RWLOCK) || defined(HAVE_UI_RWLOCK) + err = RWLOCK_RDLOCK(&rwlock->rw_lock); + PR_ASSERT(err == 0); +#else + PR_Lock(rwlock->rw_lock); + /* + * wait if write-locked or if a writer is waiting; preference for writers + */ + while ((rwlock->rw_lock_cnt < 0) || + (rwlock->rw_writer_cnt > 0)) { + rwlock->rw_reader_cnt++; + PR_WaitCondVar(rwlock->rw_reader_waitq, PR_INTERVAL_NO_TIMEOUT); + rwlock->rw_reader_cnt--; + } + /* + * Increment read-lock count + */ + rwlock->rw_lock_cnt++; + + PR_Unlock(rwlock->rw_lock); +#endif + +#ifdef _PR_RWLOCK_RANK_ORDER_DEBUG + /* + * update thread's lock rank + */ + if (rwlock->rw_rank != PR_RWLOCK_RANK_NONE) + _PR_SET_THREAD_RWLOCK_RANK(rwlock); +#endif +} + +/* +** Write-lock the RWLock. +*/ +PR_IMPLEMENT(void) +PR_RWLock_Wlock(PRRWLock *rwlock) +{ +#if defined(DEBUG) +PRThread *me = PR_GetCurrentThread(); +#endif +#if defined(HAVE_UNIX98_RWLOCK) || defined(HAVE_UI_RWLOCK) +int err; +#endif + +#ifdef _PR_RWLOCK_RANK_ORDER_DEBUG + /* + * assert that rank ordering is not violated; the rank of 'rwlock' should + * be equal to or greater than the highest rank of all the locks held by + * the thread. + */ + PR_ASSERT((rwlock->rw_rank == PR_RWLOCK_RANK_NONE) || + (rwlock->rw_rank >= _PR_GET_THREAD_RWLOCK_RANK())); +#endif + +#if defined(HAVE_UNIX98_RWLOCK) || defined(HAVE_UI_RWLOCK) + err = RWLOCK_WRLOCK(&rwlock->rw_lock); + PR_ASSERT(err == 0); +#else + PR_Lock(rwlock->rw_lock); + /* + * wait if read locked + */ + while (rwlock->rw_lock_cnt != 0) { + rwlock->rw_writer_cnt++; + PR_WaitCondVar(rwlock->rw_writer_waitq, PR_INTERVAL_NO_TIMEOUT); + rwlock->rw_writer_cnt--; + } + /* + * apply write lock + */ + rwlock->rw_lock_cnt--; + PR_ASSERT(rwlock->rw_lock_cnt == -1); +#ifdef DEBUG + PR_ASSERT(me != NULL); + rwlock->rw_owner = me; +#endif + PR_Unlock(rwlock->rw_lock); +#endif + +#ifdef _PR_RWLOCK_RANK_ORDER_DEBUG + /* + * update thread's lock rank + */ + if (rwlock->rw_rank != PR_RWLOCK_RANK_NONE) + _PR_SET_THREAD_RWLOCK_RANK(rwlock); +#endif +} + +/* +** Unlock the RW lock. +*/ +PR_IMPLEMENT(void) +PR_RWLock_Unlock(PRRWLock *rwlock) +{ +#if defined(DEBUG) +PRThread *me = PR_GetCurrentThread(); +#endif +#if defined(HAVE_UNIX98_RWLOCK) || defined(HAVE_UI_RWLOCK) +int err; +#endif + +#if defined(HAVE_UNIX98_RWLOCK) || defined(HAVE_UI_RWLOCK) + err = RWLOCK_UNLOCK(&rwlock->rw_lock); + PR_ASSERT(err == 0); +#else + PR_Lock(rwlock->rw_lock); + /* + * lock must be read or write-locked + */ + PR_ASSERT(rwlock->rw_lock_cnt != 0); + if (rwlock->rw_lock_cnt > 0) { + + /* + * decrement read-lock count + */ + rwlock->rw_lock_cnt--; + if (rwlock->rw_lock_cnt == 0) { + /* + * lock is not read-locked anymore; wakeup a waiting writer + */ + if (rwlock->rw_writer_cnt > 0) + PR_NotifyCondVar(rwlock->rw_writer_waitq); + } + } else { + PR_ASSERT(rwlock->rw_lock_cnt == -1); + + rwlock->rw_lock_cnt = 0; +#ifdef DEBUG + PR_ASSERT(rwlock->rw_owner == me); + rwlock->rw_owner = NULL; +#endif + /* + * wakeup a writer, if present; preference for writers + */ + if (rwlock->rw_writer_cnt > 0) + PR_NotifyCondVar(rwlock->rw_writer_waitq); + /* + * else, wakeup all readers, if any + */ + else if (rwlock->rw_reader_cnt > 0) + PR_NotifyAllCondVar(rwlock->rw_reader_waitq); + } + PR_Unlock(rwlock->rw_lock); +#endif + +#ifdef _PR_RWLOCK_RANK_ORDER_DEBUG + /* + * update thread's lock rank + */ + if (rwlock->rw_rank != PR_RWLOCK_RANK_NONE) + _PR_UNSET_THREAD_RWLOCK_RANK(rwlock); +#endif + return; +} + +#ifndef _PR_RWLOCK_RANK_ORDER_DEBUG + +void _PR_InitRWLocks(void) { } + +#else + +void _PR_InitRWLocks(void) +{ + /* + * allocated thread-private-data index for rwlock list + */ + if (PR_NewThreadPrivateIndex(&pr_thread_rwlock_key, + _PR_RELEASE_LOCK_STACK) == PR_FAILURE) { + pr_thread_rwlock_alloc_failed = 1; + return; + } +} + +/* + * _PR_SET_THREAD_RWLOCK_RANK + * Set a thread's lock rank, which is the highest of the ranks of all + * the locks held by the thread. Pointers to the locks are added to a + * per-thread list, which is anchored off a thread-private data key. + */ + +static void +_PR_SET_THREAD_RWLOCK_RANK(PRRWLock *rwlock) +{ +thread_rwlock_stack *lock_stack; +PRStatus rv; + + /* + * allocate a lock stack + */ + if ((lock_stack = PR_GetThreadPrivate(pr_thread_rwlock_key)) == NULL) { + lock_stack = (thread_rwlock_stack *) + PR_CALLOC(1 * sizeof(thread_rwlock_stack)); + if (lock_stack) { + rv = PR_SetThreadPrivate(pr_thread_rwlock_key, lock_stack); + if (rv == PR_FAILURE) { + PR_DELETE(lock_stack); + pr_thread_rwlock_alloc_failed = 1; + return; + } + } else { + pr_thread_rwlock_alloc_failed = 1; + return; + } + } + /* + * add rwlock to lock stack, if limit is not exceeded + */ + if (lock_stack) { + if (lock_stack->trs_index < _PR_RWLOCK_RANK_ORDER_LIMIT) + lock_stack->trs_stack[lock_stack->trs_index++] = rwlock; + } +} + +static void +_PR_RELEASE_LOCK_STACK(void *lock_stack) +{ + PR_ASSERT(lock_stack); + PR_DELETE(lock_stack); +} + +/* + * _PR_GET_THREAD_RWLOCK_RANK + * + * return thread's lock rank. If thread-private-data for the lock + * stack is not allocated, return PR_RWLOCK_RANK_NONE. + */ + +static PRUint32 +_PR_GET_THREAD_RWLOCK_RANK(void) +{ + thread_rwlock_stack *lock_stack; + + lock_stack = PR_GetThreadPrivate(pr_thread_rwlock_key); + if (lock_stack == NULL || lock_stack->trs_index == 0) + return (PR_RWLOCK_RANK_NONE); + else + return(lock_stack->trs_stack[lock_stack->trs_index - 1]->rw_rank); +} + +/* + * _PR_UNSET_THREAD_RWLOCK_RANK + * + * remove the rwlock from the lock stack. Since locks may not be + * unlocked in a FIFO order, the entire lock stack is searched. + */ + +static void +_PR_UNSET_THREAD_RWLOCK_RANK(PRRWLock *rwlock) +{ + thread_rwlock_stack *lock_stack; + int new_index = 0, index, done = 0; + + lock_stack = PR_GetThreadPrivate(pr_thread_rwlock_key); + + PR_ASSERT(lock_stack != NULL); + + for (index = lock_stack->trs_index - 1; index >= 0; index--) { + if (!done && (lock_stack->trs_stack[index] == rwlock)) { + /* + * reset the slot for rwlock + */ + lock_stack->trs_stack[index] = NULL; + done = 1; + } + /* + * search for the lowest-numbered empty slot, above which there are + * no non-empty slots + */ + if (!new_index && (lock_stack->trs_stack[index] != NULL)) + new_index = index + 1; + if (done && new_index) + break; + } + /* + * set top of stack to highest numbered empty slot + */ + lock_stack->trs_index = new_index; + +} + +#endif /* _PR_RWLOCK_RANK_ORDER_DEBUG */ |