diff options
Diffstat (limited to 'src/libs/xpcom18a4/xpcom/threads/nsAutoLock.cpp')
| -rw-r--r-- | src/libs/xpcom18a4/xpcom/threads/nsAutoLock.cpp | 435 |
1 files changed, 435 insertions, 0 deletions
diff --git a/src/libs/xpcom18a4/xpcom/threads/nsAutoLock.cpp b/src/libs/xpcom18a4/xpcom/threads/nsAutoLock.cpp new file mode 100644 index 00000000..df89408c --- /dev/null +++ b/src/libs/xpcom18a4/xpcom/threads/nsAutoLock.cpp @@ -0,0 +1,435 @@ +/* -*- 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_XXX +# 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_XXX + // 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 * 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 const PLHashAllocOps _hash_alloc_ops = { + _hash_alloc_table, _hash_free_table, + _hash_alloc_entry, _hash_free_entry +}; + +PR_STATIC_CALLBACK(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; +} + +PR_STATIC_CALLBACK(void) +OnMonitorRecycle(void* addr) +{ + PR_Lock(OrderTableLock); + PL_HashTableEnumerateEntries(OrderTable, _purge_one, addr); + PR_Unlock(OrderTableLock); +} + +PR_STATIC_CALLBACK(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(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; +} + +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; +} + +// 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_XXX + 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_XXX + NS_GetStackTrace(1) +#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_XXX + fprintf(stderr, "\n*** %s\n\nCurrent stack:\n", buf); + NS_DumpStackTrace(node, stderr); + + fputs("\nPrevious stack:\n", stderr); + NS_DumpStackTrace(vec2->mInnerSites.ElementAt(i2), stderr); + 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; +} + +#endif /* DEBUG */ + +PRMonitor* nsAutoMonitor::NewMonitor(const char* name) +{ + PRMonitor* mon = PR_NewMonitor(); +#ifdef DEBUG + if (mon && OrderTable) { + nsNamedVector* value = new nsNamedVector(name); + if (value) { + PR_Lock(OrderTableLock); + PL_HashTableAdd(OrderTable, mon, value); + PR_Unlock(OrderTableLock); + } + } +#endif + return mon; +} + +void nsAutoMonitor::DestroyMonitor(PRMonitor* mon) +{ +#ifdef DEBUG + if (OrderTable) + OnMonitorRecycle(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; +} |