The Tor Browser: nsprpub/pr/src/misc/pratom.c@6474c204b198 (annotated)

nsprpub/pr/src/misc/pratom.c@6474c204b198 (annotated)

nsprpub/pr/src/misc/pratom.c

Wed, 31 Dec 2014 06:09:35 +0100

author: Michael Schloh von Bennewitz <michael@schloh.com>
date: Wed, 31 Dec 2014 06:09:35 +0100
changeset 0: 6474c204b198
permissions: -rw-r--r--

Cloned upstream origin tor-browser at tor-browser-31.3.0esr-4.5-1-build1
revision ID fc1c9ff7c1b2defdbc039f12214767608f46423f for hacking purpose.

 /* -*- 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/. */
 /*
 **     PR Atomic operations
 */
 #include "pratom.h"
 #include "primpl.h"
 #include <string.h>
 /*
  * The following is a fallback implementation that emulates
  * atomic operations for platforms without atomic operations.
  * If a platform has atomic operations, it should define the
  * macro _PR_HAVE_ATOMIC_OPS, and the following will not be
  * compiled in.
  */
 #if !defined(_PR_HAVE_ATOMIC_OPS)
 #if defined(_PR_PTHREADS) && !defined(_PR_DCETHREADS)
 /*
  * PR_AtomicDecrement() is used in NSPR's thread-specific data
  * destructor.  Because thread-specific data destructors may be
  * invoked after a PR_Cleanup() call, we need an implementation
  * of the atomic routines that doesn't need NSPR to be initialized.
  */
 /*
  * We use a set of locks for all the emulated atomic operations.
  * By hashing on the address of the integer to be locked the
  * contention between multiple threads should be lessened.
  *
  * The number of atomic locks can be set by the environment variable
  * NSPR_ATOMIC_HASH_LOCKS
  */
 /*
  * lock counts should be a power of 2
  */
 #define DEFAULT_ATOMIC_LOCKS	16	/* should be in sync with the number of initializers
 										below */
 #define MAX_ATOMIC_LOCKS		(4 * 1024)
 static pthread_mutex_t static_atomic_locks[DEFAULT_ATOMIC_LOCKS] = {
         PTHREAD_MUTEX_INITIALIZER, PTHREAD_MUTEX_INITIALIZER,
         PTHREAD_MUTEX_INITIALIZER, PTHREAD_MUTEX_INITIALIZER,
         PTHREAD_MUTEX_INITIALIZER, PTHREAD_MUTEX_INITIALIZER,
         PTHREAD_MUTEX_INITIALIZER, PTHREAD_MUTEX_INITIALIZER,
         PTHREAD_MUTEX_INITIALIZER, PTHREAD_MUTEX_INITIALIZER,
         PTHREAD_MUTEX_INITIALIZER, PTHREAD_MUTEX_INITIALIZER,
         PTHREAD_MUTEX_INITIALIZER, PTHREAD_MUTEX_INITIALIZER,
         PTHREAD_MUTEX_INITIALIZER, PTHREAD_MUTEX_INITIALIZER };
 #ifdef DEBUG
 static PRInt32 static_hash_lock_counts[DEFAULT_ATOMIC_LOCKS];
 static PRInt32 *hash_lock_counts = static_hash_lock_counts;
 #endif
 static PRUint32	num_atomic_locks = DEFAULT_ATOMIC_LOCKS;
 static pthread_mutex_t *atomic_locks = static_atomic_locks;
 static PRUint32 atomic_hash_mask = DEFAULT_ATOMIC_LOCKS - 1;
 #define _PR_HASH_FOR_LOCK(ptr) 							\
 			((PRUint32) (((PRUptrdiff) (ptr) >> 2)	^	\
 						((PRUptrdiff) (ptr) >> 8)) &	\
 						atomic_hash_mask)
 void _PR_MD_INIT_ATOMIC()
 {
 char *eval;
 int index;
 	PR_ASSERT(PR_FloorLog2(MAX_ATOMIC_LOCKS) ==
 						PR_CeilingLog2(MAX_ATOMIC_LOCKS));
 	PR_ASSERT(PR_FloorLog2(DEFAULT_ATOMIC_LOCKS) ==
 							PR_CeilingLog2(DEFAULT_ATOMIC_LOCKS));
 	if (((eval = getenv("NSPR_ATOMIC_HASH_LOCKS")) != NULL)  &&
 		((num_atomic_locks = atoi(eval)) != DEFAULT_ATOMIC_LOCKS)) {
 		if (num_atomic_locks > MAX_ATOMIC_LOCKS)
 			num_atomic_locks = MAX_ATOMIC_LOCKS;
 		else if (num_atomic_locks < 1)
 			num_atomic_locks = 1;
 		else {
 			num_atomic_locks = PR_FloorLog2(num_atomic_locks);
 			num_atomic_locks = 1L << num_atomic_locks;
 		}
 		atomic_locks = (pthread_mutex_t *) PR_Malloc(sizeof(pthread_mutex_t) *
 						num_atomic_locks);
 		if (atomic_locks) {
 			for (index = 0; index < num_atomic_locks; index++) {
 				if (pthread_mutex_init(&atomic_locks[index], NULL)) {
 						PR_DELETE(atomic_locks);
 						atomic_locks = NULL;
 						break;
 				}
 			}
 		}
 #ifdef DEBUG
 		if (atomic_locks) {
 			hash_lock_counts = PR_CALLOC(num_atomic_locks * sizeof(PRInt32));
 			if (hash_lock_counts == NULL) {
 				PR_DELETE(atomic_locks);
 				atomic_locks = NULL;
 			}
 		}
 #endif
 		if (atomic_locks == NULL) {
 			/*
 			 *	Use statically allocated locks
 			 */
 			atomic_locks = static_atomic_locks;
 			num_atomic_locks = DEFAULT_ATOMIC_LOCKS;
 	#ifdef DEBUG
 			hash_lock_counts = static_hash_lock_counts;
 	#endif
 		}
 		atomic_hash_mask = num_atomic_locks - 1;
 	}
 	PR_ASSERT(PR_FloorLog2(num_atomic_locks) ==
 								PR_CeilingLog2(num_atomic_locks));
 }
 PRInt32
 _PR_MD_ATOMIC_INCREMENT(PRInt32 *val)
 {
     PRInt32 rv;
     PRInt32 idx = _PR_HASH_FOR_LOCK(val);
     pthread_mutex_lock(&atomic_locks[idx]);
     rv = ++(*val);
 #ifdef DEBUG
     hash_lock_counts[idx]++;
 #endif
     pthread_mutex_unlock(&atomic_locks[idx]);
     return rv;
 }
 PRInt32
 _PR_MD_ATOMIC_ADD(PRInt32 *ptr, PRInt32 val)
 {
     PRInt32 rv;
     PRInt32 idx = _PR_HASH_FOR_LOCK(ptr);
     pthread_mutex_lock(&atomic_locks[idx]);
     rv = ((*ptr) += val);
 #ifdef DEBUG
     hash_lock_counts[idx]++;
 #endif
     pthread_mutex_unlock(&atomic_locks[idx]);
     return rv;
 }
 PRInt32
 _PR_MD_ATOMIC_DECREMENT(PRInt32 *val)
 {
     PRInt32 rv;
     PRInt32 idx = _PR_HASH_FOR_LOCK(val);
     pthread_mutex_lock(&atomic_locks[idx]);
     rv = --(*val);
 #ifdef DEBUG
     hash_lock_counts[idx]++;
 #endif
     pthread_mutex_unlock(&atomic_locks[idx]);
     return rv;
 }
 PRInt32
 _PR_MD_ATOMIC_SET(PRInt32 *val, PRInt32 newval)
 {
     PRInt32 rv;
     PRInt32 idx = _PR_HASH_FOR_LOCK(val);
     pthread_mutex_lock(&atomic_locks[idx]);
     rv = *val;
     *val = newval;
 #ifdef DEBUG
     hash_lock_counts[idx]++;
 #endif
     pthread_mutex_unlock(&atomic_locks[idx]);
     return rv;
 }
 #else  /* _PR_PTHREADS && !_PR_DCETHREADS */
 /*
  * We use a single lock for all the emulated atomic operations.
  * The lock contention should be acceptable.
  */
 static PRLock *atomic_lock = NULL;
 void _PR_MD_INIT_ATOMIC(void)
 {
     if (atomic_lock == NULL) {
         atomic_lock = PR_NewLock();
     }
 }
 PRInt32
 _PR_MD_ATOMIC_INCREMENT(PRInt32 *val)
 {
     PRInt32 rv;
     if (!_pr_initialized) {
         _PR_ImplicitInitialization();
     }
     PR_Lock(atomic_lock);
     rv = ++(*val);
     PR_Unlock(atomic_lock);
     return rv;
 }
 PRInt32
 _PR_MD_ATOMIC_ADD(PRInt32 *ptr, PRInt32 val)
 {
     PRInt32 rv;
     if (!_pr_initialized) {
         _PR_ImplicitInitialization();
     }
     PR_Lock(atomic_lock);
     rv = ((*ptr) += val);
     PR_Unlock(atomic_lock);
     return rv;
 }
 PRInt32
 _PR_MD_ATOMIC_DECREMENT(PRInt32 *val)
 {
     PRInt32 rv;
     if (!_pr_initialized) {
         _PR_ImplicitInitialization();
     }
     PR_Lock(atomic_lock);
     rv = --(*val);
     PR_Unlock(atomic_lock);
     return rv;
 }
 PRInt32
 _PR_MD_ATOMIC_SET(PRInt32 *val, PRInt32 newval)
 {
     PRInt32 rv;
     if (!_pr_initialized) {
         _PR_ImplicitInitialization();
     }
     PR_Lock(atomic_lock);
     rv = *val;
     *val = newval;
     PR_Unlock(atomic_lock);
     return rv;
 }
 #endif  /* _PR_PTHREADS && !_PR_DCETHREADS */
 #endif  /* !_PR_HAVE_ATOMIC_OPS */
 void _PR_InitAtomic(void)
 {
     _PR_MD_INIT_ATOMIC();
 }
 PR_IMPLEMENT(PRInt32)
 PR_AtomicIncrement(PRInt32 *val)
 {
     return _PR_MD_ATOMIC_INCREMENT(val);
 }
 PR_IMPLEMENT(PRInt32)
 PR_AtomicDecrement(PRInt32 *val)
 {
     return _PR_MD_ATOMIC_DECREMENT(val);
 }
 PR_IMPLEMENT(PRInt32)
 PR_AtomicSet(PRInt32 *val, PRInt32 newval)
 {
     return _PR_MD_ATOMIC_SET(val, newval);
 }
 PR_IMPLEMENT(PRInt32)
 PR_AtomicAdd(PRInt32 *ptr, PRInt32 val)
 {
     return _PR_MD_ATOMIC_ADD(ptr, val);
 }
 /*
  * For platforms, which don't support the CAS (compare-and-swap) instruction
  * (or an equivalent), the stack operations are implemented by use of PRLock
  */
 PR_IMPLEMENT(PRStack *)
 PR_CreateStack(const char *stack_name)
 {
 PRStack *stack;
     if (!_pr_initialized) {
         _PR_ImplicitInitialization();
     }
     if ((stack = PR_NEW(PRStack)) == NULL) {
 		return NULL;
 	}
 	if (stack_name) {
 		stack->prstk_name = (char *) PR_Malloc(strlen(stack_name) + 1);
 		if (stack->prstk_name == NULL) {
 			PR_DELETE(stack);
 			return NULL;
 		}
 		strcpy(stack->prstk_name, stack_name);
 	} else
 		stack->prstk_name = NULL;
 #ifndef _PR_HAVE_ATOMIC_CAS
     stack->prstk_lock = PR_NewLock();
 	if (stack->prstk_lock == NULL) {
 		PR_Free(stack->prstk_name);
 		PR_DELETE(stack);
 		return NULL;
 	}
 #endif /* !_PR_HAVE_ATOMIC_CAS */
 	stack->prstk_head.prstk_elem_next = NULL;
     return stack;
 }
 PR_IMPLEMENT(PRStatus)
 PR_DestroyStack(PRStack *stack)
 {
 	if (stack->prstk_head.prstk_elem_next != NULL) {
 		PR_SetError(PR_INVALID_STATE_ERROR, 0);
 		return PR_FAILURE;
 	}
 	if (stack->prstk_name)
 		PR_Free(stack->prstk_name);
 #ifndef _PR_HAVE_ATOMIC_CAS
 	PR_DestroyLock(stack->prstk_lock);
 #endif /* !_PR_HAVE_ATOMIC_CAS */
 	PR_DELETE(stack);
 	return PR_SUCCESS;
 }
 #ifndef _PR_HAVE_ATOMIC_CAS
 PR_IMPLEMENT(void)
 PR_StackPush(PRStack *stack, PRStackElem *stack_elem)
 {
     PR_Lock(stack->prstk_lock);
 	stack_elem->prstk_elem_next = stack->prstk_head.prstk_elem_next;
 	stack->prstk_head.prstk_elem_next = stack_elem;
     PR_Unlock(stack->prstk_lock);
     return;
 }
 PR_IMPLEMENT(PRStackElem *)
 PR_StackPop(PRStack *stack)
 {
 PRStackElem *element;
     PR_Lock(stack->prstk_lock);
 	element = stack->prstk_head.prstk_elem_next;
 	if (element != NULL) {
 		stack->prstk_head.prstk_elem_next = element->prstk_elem_next;
 		element->prstk_elem_next = NULL;	/* debugging aid */
 	}
     PR_Unlock(stack->prstk_lock);
     return element;
 }
 #endif /* !_PR_HAVE_ATOMIC_CAS */

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nsprpub/pr/src/misc/pratom.c@6474c204b198 (annotated)

nsprpub/pr/src/misc/pratom.c