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/* -*- 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
#include "primpl.h"
#include <string.h>
#if defined(HPUX) && defined(_PR_PTHREADS)
#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 */