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gecko-dev/xpcom/glue/nsAutoLock.cpp

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/* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4 -*- */
/* ***** BEGIN LICENSE BLOCK *****
* Version: MPL 1.1/GPL 2.0/LGPL 2.1
*
* The contents of this file are subject to the Mozilla 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/MPL/
*
* 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.
*
* The Original Code is mozilla.org code.
*
* The Initial Developer of the Original Code is
* Netscape Communications Corporation.
* Portions created by the Initial Developer are Copyright (C) 1998
* the Initial Developer. All Rights Reserved.
*
* Contributor(s):
*
* Alternatively, the contents of this file may be used under the terms of
* either of the GNU General Public License Version 2 or later (the "GPL"),
* or the GNU Lesser General Public License Version 2.1 or later (the "LGPL"),
* in which case the provisions of the GPL or the LGPL are applicable instead
* of those above. If you wish to allow use of your version of this file only
* under the terms of either the GPL or the LGPL, and not to allow others to
* use your version of this file under the terms of the MPL, indicate your
* decision by deleting the provisions above and replace them with the notice
* and other provisions required by the GPL or the LGPL. If you do not delete
* the provisions above, a recipient may use your version of this file under
* the terms of any one of the MPL, the GPL or the LGPL.
*
* ***** END LICENSE BLOCK ***** */
#include "nsAutoLock.h"
#ifdef DEBUG
#include "plhash.h"
#include "prprf.h"
#include "prlock.h"
#include "prthread.h"
#include "nsDebug.h"
#include "nsVoidArray.h"
#ifdef NS_TRACE_MALLOC
# include <stdio.h>
# include "nsTraceMalloc.h"
#endif
static PRUintn LockStackTPI = (PRUintn)-1;
static PLHashTable* OrderTable = 0;
static PRLock* OrderTableLock = 0;
static const char* const LockTypeNames[] = {"Lock", "Monitor", "CMonitor"};
struct nsNamedVector : public nsVoidArray {
const char* mName;
#ifdef NS_TRACE_MALLOC
// Callsites for the inner locks/monitors stored in our base nsVoidArray.
// This array parallels our base nsVoidArray.
nsVoidArray mInnerSites;
#endif
nsNamedVector(const char* name = 0, PRUint32 initialSize = 0)
: nsVoidArray(initialSize),
mName(name)
{
}
};
static void *
_hash_alloc_table(void *pool, PRSize size)
{
return operator new(size);
}
static void
_hash_free_table(void *pool, void *item)
{
operator delete(item);
}
static PLHashEntry *
_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
_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 const PLHashAllocOps _hash_alloc_ops = {
_hash_alloc_table, _hash_free_table,
_hash_alloc_entry, _hash_free_entry
};
static PRIntn
_purge_one(PLHashEntry* he, PRIntn cnt, void* arg)
{
nsNamedVector* vec = (nsNamedVector*) he->value;
if (he->key == arg)
return HT_ENUMERATE_REMOVE;
vec->RemoveElement(arg);
return HT_ENUMERATE_NEXT;
}
static void
OnSemaphoreRecycle(void* addr)
{
if (OrderTable) {
PR_Lock(OrderTableLock);
PL_HashTableEnumerateEntries(OrderTable, _purge_one, addr);
PR_Unlock(OrderTableLock);
}
}
static PLHashNumber
_hash_pointer(const void* key)
{
return PLHashNumber(NS_PTR_TO_INT32(key)) >> 2;
}
// Must be single-threaded here, early in primordial thread.
static void InitAutoLockStatics()
{
(void) PR_NewThreadPrivateIndex(&LockStackTPI, 0);
OrderTable = PL_NewHashTable(64, _hash_pointer,
PL_CompareValues, PL_CompareValues,
&_hash_alloc_ops, 0);
if (OrderTable && !(OrderTableLock = PR_NewLock())) {
PL_HashTableDestroy(OrderTable);
OrderTable = 0;
}
PR_CSetOnMonitorRecycle(OnSemaphoreRecycle);
}
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;
}
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;
nsNamedVector* vec = new nsNamedVector();
if (vec)
PL_HashTableRawAdd(table, hep, hash, key, vec);
return vec;
}
static void OnSemaphoreCreated(const void* key, const char* name )
{
if (key && OrderTable) {
nsNamedVector* value = new nsNamedVector(name);
if (value) {
PR_Lock(OrderTableLock);
PL_HashTableAdd(OrderTable, key, value);
PR_Unlock(OrderTableLock);
}
}
}
// We maintain an acyclic graph in OrderTable, 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);
if (addr == goal || Reachable(table, goal, addr))
return PR_TRUE;
}
return PR_FALSE;
}
static PRBool WellOrdered(const void* addr1, const void* addr2,
const void *callsite2, PRUint32* index2p,
nsNamedVector** vec1p, nsNamedVector** vec2p)
{
PRBool rv = PR_TRUE;
PLHashTable* table = OrderTable;
if (!table) return rv;
PR_Lock(OrderTableLock);
// Check whether we've already asserted (addr1 < addr2).
nsNamedVector* vec1 = GetVector(table, addr1);
if (vec1) {
PRUint32 i, n;
for (i = 0, n = vec1->Count(); i < n; i++)
if (vec1->ElementAt(i) == addr2)
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);
PR_ASSERT(addri);
if (addri == addr1 || Reachable(table, addr1, addri)) {
*index2p = i;
*vec1p = vec1;
*vec2p = vec2;
rv = PR_FALSE;
break;
}
}
if (rv) {
// Assert (addr1 < addr2) into the order table.
// XXX fix plvector/nsVector to use const void*
vec1->AppendElement((void*) addr2);
#ifdef NS_TRACE_MALLOC
vec1->mInnerSites.AppendElement((void*) callsite2);
#endif
}
}
}
}
PR_Unlock(OrderTableLock);
return rv;
}
nsAutoLockBase::nsAutoLockBase(void* addr, nsAutoLockType type)
{
if (LockStackTPI == PRUintn(-1))
InitAutoLockStatics();
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 if (!addr) {
// Ignore null addresses: the caller promises not to use the
// lock at all, and NSPR will assert if you enter it.
} else {
const void* node =
#ifdef NS_TRACE_MALLOC
(const void*)NS_TraceMallocGetStackTrace();
#else
nsnull
#endif
;
nsNamedVector* vec1;
nsNamedVector* vec2;
PRUint32 i2;
if (!WellOrdered(stackTop->mAddr, addr, node, &i2, &vec1, &vec2)) {
char buf[128];
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);
#ifdef NS_TRACE_MALLOC
fprintf(stderr, "\n*** %s\n\nCurrent stack:\n", buf);
NS_TraceMallocPrintStackTrace(stderr,
NS_TraceMallocGetStackTrace());
fputs("\nPrevious stack:\n", stderr);
NS_TraceMallocPrintStackTrace(stderr,
(nsTMStackTraceIDStruct *)vec2->mInnerSites.ElementAt(i2));
putc('\n', stderr);
#endif
NS_ERROR(buf);
}
}
}
mAddr = addr;
mDown = stackTop;
mType = type;
if (mAddr)
(void) PR_SetThreadPrivate(LockStackTPI, this);
}
nsAutoLockBase::~nsAutoLockBase()
{
if (mAddr)
(void) PR_SetThreadPrivate(LockStackTPI, mDown);
}
void nsAutoLockBase::Show()
{
if (!mAddr)
return;
nsAutoLockBase* curr = (nsAutoLockBase*) PR_GetThreadPrivate(LockStackTPI);
nsAutoLockBase* prev = nsnull;
while (curr != mDown) {
prev = curr;
curr = prev->mDown;
}
if (!prev)
PR_SetThreadPrivate(LockStackTPI, this);
else
prev->mDown = this;
}
void nsAutoLockBase::Hide()
{
if (!mAddr)
return;
nsAutoLockBase* curr = (nsAutoLockBase*) PR_GetThreadPrivate(LockStackTPI);
nsAutoLockBase* prev = nsnull;
while (curr != this) {
prev = curr;
curr = prev->mDown;
}
if (!prev)
PR_SetThreadPrivate(LockStackTPI, mDown);
else
prev->mDown = mDown;
}
nsAutoUnlockBase::nsAutoUnlockBase(void* addr)
{
if (addr)
{
nsAutoLockBase* curr = (nsAutoLockBase*) PR_GetThreadPrivate(LockStackTPI);
while (curr && curr->mAddr != addr)
curr = curr->mDown;
mLock = curr;
}
else
mLock = nsnull;
if (mLock)
mLock->Hide();
}
nsAutoUnlockBase::~nsAutoUnlockBase()
{
if (mLock)
mLock->Show();
}
#endif /* DEBUG */
PRLock* nsAutoLock::NewLock(const char* name)
{
PRLock* lock = PR_NewLock();
#ifdef DEBUG
OnSemaphoreCreated(lock, name);
#endif
return lock;
}
void nsAutoLock::DestroyLock(PRLock* lock)
{
#ifdef DEBUG
OnSemaphoreRecycle(lock);
#endif
PR_DestroyLock(lock);
}
PRMonitor* nsAutoMonitor::NewMonitor(const char* name)
{
PRMonitor* mon = PR_NewMonitor();
#ifdef DEBUG
OnSemaphoreCreated(mon, name);
#endif
return mon;
}
void nsAutoMonitor::DestroyMonitor(PRMonitor* mon)
{
#ifdef DEBUG
OnSemaphoreRecycle(mon);
#endif
PR_DestroyMonitor(mon);
}
void nsAutoMonitor::Enter()
{
#ifdef DEBUG
if (!mAddr) {
NS_ERROR("It is not legal to enter a null monitor");
return;
}
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);
mLockCount += 1;
}
void nsAutoMonitor::Exit()
{
#ifdef DEBUG
if (!mAddr) {
NS_ERROR("It is not legal to exit a null monitor");
return;
}
(void) PR_SetThreadPrivate(LockStackTPI, mDown);
#endif
PRStatus status = PR_ExitMonitor(mMonitor);
NS_ASSERTION(status == PR_SUCCESS, "PR_ExitMonitor failed");
mLockCount -= 1;
}
// 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);
mLockCount += 1;
}
void nsAutoCMonitor::Exit()
{
#ifdef DEBUG
(void) PR_SetThreadPrivate(LockStackTPI, mDown);
#endif
PRStatus status = PR_CExitMonitor(mLockObject);
NS_ASSERTION(status == PR_SUCCESS, "PR_CExitMonitor failed");
mLockCount -= 1;
}
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