The Tor Browser: nsprpub/pr/src/threads/prrwlock.c@ca08bd8f51b2 (annotated)

nsprpub/pr/src/threads/prrwlock.c@ca08bd8f51b2 (annotated)

nsprpub/pr/src/threads/prrwlock.c

Wed, 31 Dec 2014 06:55:46 +0100

author: Michael Schloh von Bennewitz <michael@schloh.com>
date: Wed, 31 Dec 2014 06:55:46 +0100
changeset 1: ca08bd8f51b2
permissions: -rw-r--r--

Added tag TORBROWSER_REPLICA for changeset 6474c204b198

 /* -*- 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 */

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nsprpub/pr/src/threads/prrwlock.c@ca08bd8f51b2 (annotated)

nsprpub/pr/src/threads/prrwlock.c