gecko-dev/xpcom/threads/nsAutoLock.cpp

337 строки
9.7 KiB
C++
Исходник Обычный вид История

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/* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4 -*-
*
* The contents of this file are subject to the Netscape Public
* License Version 1.1 (the "License"); you may not use this file
* except in compliance with the License. You may obtain a copy of
* the License at http://www.mozilla.org/NPL/
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*
* Software distributed under the License is distributed on an "AS
* IS" basis, WITHOUT WARRANTY OF ANY KIND, either express or
* implied. See the License for the specific language governing
* rights and limitations under the License.
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*
* The Original Code is mozilla.org code.
*
* The Initial Developer of the Original Code is Netscape
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* Communications Corporation. Portions created by Netscape are
* Copyright (C) 1998 Netscape Communications Corporation. All
* Rights Reserved.
*
* Contributor(s):
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*/
#include "nsAutoLock.h"
#ifdef DEBUG
#include "plhash.h"
#include "prprf.h"
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#include "prlock.h"
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#include "prthread.h"
#include "nsDebug.h"
#include "nsVoidArray.h"
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static PRUintn LockStackTPI = (PRUintn)-1;
static PLHashTable* OrderTable = 0;
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static PRLock* OrderTableLock = 0;
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static const char* LockTypeNames[] = {"Lock", "Monitor", "CMonitor"};
struct nsNamedVector : public nsVoidArray {
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const char* mName;
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nsNamedVector(const char* name = 0, PRUint32 initialSize = 0)
: nsVoidArray(initialSize),
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mName(name)
{
}
};
static void * PR_CALLBACK
_hash_alloc_table(void *pool, PRSize size)
{
return operator new(size);
}
static void PR_CALLBACK
_hash_free_table(void *pool, void *item)
{
operator delete(item);
}
static PLHashEntry * PR_CALLBACK
_hash_alloc_entry(void *pool, const void *key)
{
return new PLHashEntry;
}
/*
* Because monitors and locks may be associated with an nsAutoLockBase,
* without having had their associated nsNamedVector created explicitly in
* nsAutoMonitor::NewMonitor/DeleteMonitor, we need to provide a freeEntry
* PLHashTable hook, to avoid leaking nsNamedVectors which are replaced by
* nsAutoMonitor::NewMonitor.
*
* There is still a problem with the OrderTable containing orphaned
* nsNamedVector entries, for manually created locks wrapped by nsAutoLocks.
* (there should be no manually created monitors wrapped by nsAutoMonitors:
* you should use nsAutoMonitor::NewMonitor and nsAutoMonitor::DestroyMonitor
* instead of PR_NewMonitor and PR_DestroyMonitor). These lock vectors don't
* strictly leak, as they are killed on shutdown, but there are unnecessary
* named vectors in the hash table that outlive their associated locks.
*
* XXX so we should have nsLock, nsMonitor, etc. and strongly type their
* XXX nsAutoXXX counterparts to take only the non-auto types as inputs
*/
static void PR_CALLBACK
_hash_free_entry(void *pool, PLHashEntry *entry, PRUintn flag)
{
nsNamedVector* vec = (nsNamedVector*) entry->value;
if (vec) {
entry->value = 0;
delete vec;
}
if (flag == HT_FREE_ENTRY)
delete entry;
}
static PLHashAllocOps _hash_alloc_ops = {
_hash_alloc_table, _hash_free_table,
_hash_alloc_entry, _hash_free_entry
};
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PR_STATIC_CALLBACK(PRIntn)
_purge_one(PLHashEntry* he, PRIntn cnt, void* arg)
{
nsNamedVector* vec = (nsNamedVector*) he->value;
if (he->key == arg)
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return HT_ENUMERATE_REMOVE;
vec->RemoveElement(arg);
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return HT_ENUMERATE_NEXT;
}
PR_STATIC_CALLBACK(void)
OnMonitorRecycle(void* addr)
{
PR_Lock(OrderTableLock);
PL_HashTableEnumerateEntries(OrderTable, _purge_one, addr);
PR_Unlock(OrderTableLock);
}
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PR_STATIC_CALLBACK(PLHashNumber)
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_hash_pointer(const void* key)
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{
return PLHashNumber(key) >> 2;
}
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// Must be single-threaded here, early in primordial thread.
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static void InitAutoLockStatics()
{
(void) PR_NewThreadPrivateIndex(&LockStackTPI, 0);
OrderTable = PL_NewHashTable(64, _hash_pointer,
PL_CompareValues, PL_CompareValues,
&_hash_alloc_ops, 0);
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if (OrderTable && !(OrderTableLock = PR_NewLock())) {
PL_HashTableDestroy(OrderTable);
OrderTable = 0;
}
PR_CSetOnMonitorRecycle(OnMonitorRecycle);
}
void _FreeAutoLockStatics()
{
PLHashTable* table = OrderTable;
if (!table) return;
// Called at shutdown, so we don't need to lock.
PR_CSetOnMonitorRecycle(0);
PR_DestroyLock(OrderTableLock);
OrderTableLock = 0;
PL_HashTableDestroy(table);
OrderTable = 0;
}
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static nsNamedVector* GetVector(PLHashTable* table, const void* key)
{
PLHashNumber hash = _hash_pointer(key);
PLHashEntry** hep = PL_HashTableRawLookup(table, hash, key);
PLHashEntry* he = *hep;
if (he)
return (nsNamedVector*) he->value;
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nsNamedVector* vec = new nsNamedVector();
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if (vec)
PL_HashTableRawAdd(table, hep, hash, key, vec);
return vec;
}
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// We maintain an acyclic graph in order table, so recursion can't diverge
static PRBool Reachable(PLHashTable* table, const void* goal, const void* start)
{
PR_ASSERT(goal);
PR_ASSERT(start);
nsNamedVector* vec = GetVector(table, start);
for (PRUint32 i = 0, n = vec->Count(); i < n; i++) {
void* addr = vec->ElementAt(i);
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if (addr == goal || Reachable(table, goal, addr))
return PR_TRUE;
}
return PR_FALSE;
}
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static PRBool WellOrdered(const void* addr1, const void* addr2,
nsNamedVector** vec1p, nsNamedVector** vec2p)
{
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PRBool rv = PR_TRUE;
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PLHashTable* table = OrderTable;
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if (!table) return rv;
PR_Lock(OrderTableLock);
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PRUint32 i, n;
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// Check whether we've already asserted (addr1 < addr2).
nsNamedVector* vec1 = GetVector(table, addr1);
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if (vec1) {
for (i = 0, n = vec1->Count(); i < n; i++)
if (vec1->ElementAt(i) == addr2)
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break;
if (i == n) {
// Now check for (addr2 < addr1) and return false if so.
nsNamedVector* vec2 = GetVector(table, addr2);
if (vec2) {
for (i = 0, n = vec2->Count(); i < n; i++) {
void* addri = vec2->ElementAt(i);
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PR_ASSERT(addri);
if (addri == addr1 || Reachable(table, addr1, addri)) {
*vec1p = vec1;
*vec2p = vec2;
rv = PR_FALSE;
break;
}
}
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if (rv) {
// Assert (addr1 < addr2) into the order table.
// XXX fix plvector/nsVector to use const void*
vec1->AppendElement((void*) addr2);
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}
}
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}
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}
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PR_Unlock(OrderTableLock);
return rv;
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}
nsAutoLockBase::nsAutoLockBase(void* addr, nsAutoLockType type)
{
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if (LockStackTPI == PRUintn(-1))
InitAutoLockStatics();
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nsAutoLockBase* stackTop =
(nsAutoLockBase*) PR_GetThreadPrivate(LockStackTPI);
if (stackTop) {
if (stackTop->mAddr == addr) {
// Ignore reentry: it's legal for monitors, and NSPR will assert
// if you reenter a PRLock.
} else {
nsNamedVector* vec1;
nsNamedVector* vec2;
if (!WellOrdered(stackTop->mAddr, addr, &vec1, &vec2)) {
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char buf[128];
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PR_snprintf(buf, sizeof buf,
"potential deadlock between %s%s@%p and %s%s@%p",
vec1->mName ? vec1->mName : "",
LockTypeNames[stackTop->mType],
stackTop->mAddr,
vec2->mName ? vec2->mName : "",
LockTypeNames[type],
addr);
NS_ERROR(buf);
}
}
}
mAddr = addr;
mDown = stackTop;
mType = type;
(void) PR_SetThreadPrivate(LockStackTPI, this);
}
nsAutoLockBase::~nsAutoLockBase()
{
(void) PR_SetThreadPrivate(LockStackTPI, mDown);
}
#endif /* DEBUG */
PRMonitor* nsAutoMonitor::NewMonitor(const char* name)
{
PRMonitor* mon = PR_NewMonitor();
#ifdef DEBUG
if (mon && OrderTable) {
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nsNamedVector* value = new nsNamedVector(name);
if (value) {
PR_Lock(OrderTableLock);
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PL_HashTableAdd(OrderTable, mon, value);
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PR_Unlock(OrderTableLock);
}
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}
#endif
return mon;
}
void nsAutoMonitor::DestroyMonitor(PRMonitor* mon)
{
#ifdef DEBUG
if (OrderTable)
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OnMonitorRecycle(mon);
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#endif
PR_DestroyMonitor(mon);
}
void nsAutoMonitor::Enter()
{
#ifdef DEBUG
nsAutoLockBase* stackTop =
(nsAutoLockBase*) PR_GetThreadPrivate(LockStackTPI);
NS_ASSERTION(stackTop == mDown, "non-LIFO nsAutoMonitor::Enter");
mDown = stackTop;
(void) PR_SetThreadPrivate(LockStackTPI, this);
#endif
PR_EnterMonitor(mMonitor);
}
void nsAutoMonitor::Exit()
{
#ifdef DEBUG
(void) PR_SetThreadPrivate(LockStackTPI, mDown);
#endif
PRStatus status = PR_ExitMonitor(mMonitor);
NS_ASSERTION(status == PR_SUCCESS, "PR_ExitMonitor failed");
}
// XXX we don't worry about cached monitors being destroyed behind our back.
// XXX current NSPR (mozilla/nsprpub/pr/src/threads/prcmon.c) never destroys
// XXX a cached monitor! potential resource pig in conjunction with necko...
void nsAutoCMonitor::Enter()
{
#ifdef DEBUG
nsAutoLockBase* stackTop =
(nsAutoLockBase*) PR_GetThreadPrivate(LockStackTPI);
NS_ASSERTION(stackTop == mDown, "non-LIFO nsAutoCMonitor::Enter");
mDown = stackTop;
(void) PR_SetThreadPrivate(LockStackTPI, this);
#endif
PR_CEnterMonitor(mLockObject);
}
void nsAutoCMonitor::Exit()
{
#ifdef DEBUG
(void) PR_SetThreadPrivate(LockStackTPI, mDown);
#endif
PRStatus status = PR_CExitMonitor(mLockObject);
NS_ASSERTION(status == PR_SUCCESS, "PR_CExitMonitor failed");
}