mirror of
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386 lines
12 KiB
C++
386 lines
12 KiB
C++
/* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4 -*-
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* vim: sw=4 ts=4 et :
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* ***** BEGIN LICENSE BLOCK *****
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* Version: MPL 1.1/GPL 2.0/LGPL 2.1
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*
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* The contents of this file are subject to the Mozilla Public License Version
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* 1.1 (the "License"); you may not use this file except in compliance with
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* the License. You may obtain a copy of the License at
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* http://www.mozilla.org/MPL/
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*
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* Software distributed under the License is distributed on an "AS IS" basis,
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* WITHOUT WARRANTY OF ANY KIND, either express or implied. See the License
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* for the specific language governing rights and limitations under the
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* License.
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*
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* The Original Code is mozilla.org code.
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*
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* The Initial Developer of the Original Code is
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* Netscape Communications Corporation.
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* Portions created by the Initial Developer are Copyright (C) 1998
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* the Initial Developer. All Rights Reserved.
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*
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* Contributor(s):
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* Chris Jones <jones.chris.g@gmail.com>
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*
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* Alternatively, the contents of this file may be used under the terms of
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* either of the GNU General Public License Version 2 or later (the "GPL"),
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* or the GNU Lesser General Public License Version 2.1 or later (the "LGPL"),
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* in which case the provisions of the GPL or the LGPL are applicable instead
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* of those above. If you wish to allow use of your version of this file only
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* under the terms of either the GPL or the LGPL, and not to allow others to
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* use your version of this file under the terms of the MPL, indicate your
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* decision by deleting the provisions above and replace them with the notice
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* and other provisions required by the GPL or the LGPL. If you do not delete
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* the provisions above, a recipient may use your version of this file under
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* the terms of any one of the MPL, the GPL or the LGPL.
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*
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* ***** END LICENSE BLOCK ***** */
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#include "mozilla/BlockingResourceBase.h"
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#ifdef DEBUG
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#include "nsAutoPtr.h"
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#include "mozilla/CondVar.h"
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#include "mozilla/ReentrantMonitor.h"
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#include "mozilla/Mutex.h"
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#endif // ifdef DEBUG
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namespace mozilla {
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//
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// BlockingResourceBase implementation
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//
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// static members
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const char* const BlockingResourceBase::kResourceTypeName[] =
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{
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// needs to be kept in sync with BlockingResourceType
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"Mutex", "ReentrantMonitor", "CondVar"
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};
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#ifdef DEBUG
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PRCallOnceType BlockingResourceBase::sCallOnce;
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PRUintn BlockingResourceBase::sResourceAcqnChainFrontTPI = (PRUintn)-1;
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BlockingResourceBase::DDT* BlockingResourceBase::sDeadlockDetector;
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bool
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BlockingResourceBase::DeadlockDetectorEntry::Print(
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const DDT::ResourceAcquisition& aFirstSeen,
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nsACString& out,
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bool aPrintFirstSeenCx) const
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{
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CallStack lastAcquisition = mAcquisitionContext; // RACY, but benign
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bool maybeCurrentlyAcquired = (CallStack::kNone != lastAcquisition);
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CallStack printAcquisition =
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(aPrintFirstSeenCx || !maybeCurrentlyAcquired) ?
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aFirstSeen.mCallContext : lastAcquisition;
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fprintf(stderr, "--- %s : %s",
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kResourceTypeName[mType], mName);
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out += BlockingResourceBase::kResourceTypeName[mType];
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out += " : ";
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out += mName;
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if (maybeCurrentlyAcquired) {
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fputs(" (currently acquired)\n", stderr);
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out += " (currently acquired)\n";
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}
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fputs(" calling context\n", stderr);
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printAcquisition.Print(stderr);
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return maybeCurrentlyAcquired;
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}
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BlockingResourceBase::BlockingResourceBase(
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const char* aName,
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BlockingResourceBase::BlockingResourceType aType)
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{
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// PR_CallOnce guaranatees that InitStatics is called in a
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// thread-safe way
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if (PR_SUCCESS != PR_CallOnce(&sCallOnce, InitStatics))
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NS_RUNTIMEABORT("can't initialize blocking resource static members");
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mDDEntry = new BlockingResourceBase::DeadlockDetectorEntry(aName, aType);
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if (!mDDEntry)
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NS_RUNTIMEABORT("can't allocated deadlock detector entry");
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mChainPrev = 0;
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sDeadlockDetector->Add(mDDEntry);
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}
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BlockingResourceBase::~BlockingResourceBase()
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{
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// we don't check for really obviously bad things like freeing
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// Mutexes while they're still locked. it is assumed that the
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// base class, or its underlying primitive, will check for such
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// stupid mistakes.
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mChainPrev = 0; // racy only for stupidly buggy client code
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mDDEntry = 0; // owned by deadlock detector
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}
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void
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BlockingResourceBase::CheckAcquire(const CallStack& aCallContext)
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{
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if (eCondVar == mDDEntry->mType) {
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NS_NOTYETIMPLEMENTED(
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"FIXME bug 456272: annots. to allow CheckAcquire()ing condvars");
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return;
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}
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BlockingResourceBase* chainFront = ResourceChainFront();
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nsAutoPtr<DDT::ResourceAcquisitionArray> cycle(
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sDeadlockDetector->CheckAcquisition(
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chainFront ? chainFront->mDDEntry : 0, mDDEntry,
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aCallContext));
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if (!cycle)
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return;
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fputs("###!!! ERROR: Potential deadlock detected:\n", stderr);
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nsCAutoString out("Potential deadlock detected:\n");
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bool maybeImminent = PrintCycle(cycle, out);
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if (maybeImminent) {
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fputs("\n###!!! Deadlock may happen NOW!\n\n", stderr);
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out.Append("\n###!!! Deadlock may happen NOW!\n\n");
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} else {
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fputs("\nDeadlock may happen for some other execution\n\n",
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stderr);
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out.Append("\nDeadlock may happen for some other execution\n\n");
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}
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// XXX can customize behavior on whether we /think/ deadlock is
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// XXX about to happen. for example:
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// XXX if (maybeImminent)
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// NS_RUNTIMEABORT(out.get());
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NS_ERROR(out.get());
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}
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void
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BlockingResourceBase::Acquire(const CallStack& aCallContext)
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{
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if (eCondVar == mDDEntry->mType) {
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NS_NOTYETIMPLEMENTED(
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"FIXME bug 456272: annots. to allow Acquire()ing condvars");
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return;
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}
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NS_ASSERTION(mDDEntry->mAcquisitionContext == CallStack::kNone,
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"reacquiring already acquired resource");
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ResourceChainAppend(ResourceChainFront());
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mDDEntry->mAcquisitionContext = aCallContext;
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}
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void
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BlockingResourceBase::Release()
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{
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if (eCondVar == mDDEntry->mType) {
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NS_NOTYETIMPLEMENTED(
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"FIXME bug 456272: annots. to allow Release()ing condvars");
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return;
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}
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BlockingResourceBase* chainFront = ResourceChainFront();
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NS_ASSERTION(chainFront
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&& CallStack::kNone != mDDEntry->mAcquisitionContext,
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"Release()ing something that hasn't been Acquire()ed");
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if (chainFront == this) {
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ResourceChainRemove();
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}
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else {
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// not an error, but makes code hard to reason about.
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NS_WARNING("Resource acquired at calling context\n");
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mDDEntry->mAcquisitionContext.Print(stderr);
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NS_WARNING("\nis being released in non-LIFO order; why?");
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// remove this resource from wherever it lives in the chain
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// we walk backwards in order of acquisition:
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// (1) ...node<-prev<-curr...
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// / /
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// (2) ...prev<-curr...
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BlockingResourceBase* curr = chainFront;
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BlockingResourceBase* prev = nsnull;
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while (curr && (prev = curr->mChainPrev) && (prev != this))
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curr = prev;
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if (prev == this)
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curr->mChainPrev = prev->mChainPrev;
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}
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mDDEntry->mAcquisitionContext = CallStack::kNone;
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}
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bool
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BlockingResourceBase::PrintCycle(const DDT::ResourceAcquisitionArray* aCycle,
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nsACString& out)
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{
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NS_ASSERTION(aCycle->Length() > 1, "need > 1 element for cycle!");
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bool maybeImminent = true;
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fputs("=== Cyclical dependency starts at\n", stderr);
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out += "Cyclical dependency starts at\n";
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const DDT::ResourceAcquisition res = aCycle->ElementAt(0);
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maybeImminent &= res.mResource->Print(res, out);
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DDT::ResourceAcquisitionArray::index_type i;
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DDT::ResourceAcquisitionArray::size_type len = aCycle->Length();
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const DDT::ResourceAcquisition* it = 1 + aCycle->Elements();
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for (i = 1; i < len - 1; ++i, ++it) {
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fputs("\n--- Next dependency:\n", stderr);
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out += "\nNext dependency:\n";
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maybeImminent &= it->mResource->Print(*it, out);
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}
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fputs("\n=== Cycle completed at\n", stderr);
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out += "Cycle completed at\n";
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it->mResource->Print(*it, out, true);
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return maybeImminent;
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}
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//
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// Debug implementation of Mutex
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void
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Mutex::Lock()
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{
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CallStack callContext = CallStack();
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CheckAcquire(callContext);
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PR_Lock(mLock);
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Acquire(callContext); // protected by mLock
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}
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void
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Mutex::Unlock()
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{
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Release(); // protected by mLock
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PRStatus status = PR_Unlock(mLock);
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NS_ASSERTION(PR_SUCCESS == status, "bad Mutex::Unlock()");
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}
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//
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// Debug implementation of ReentrantMonitor
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void
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ReentrantMonitor::Enter()
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{
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BlockingResourceBase* chainFront = ResourceChainFront();
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// the code below implements monitor reentrancy semantics
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if (this == chainFront) {
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// immediately re-entered the monitor: acceptable
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PR_EnterMonitor(mReentrantMonitor);
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++mEntryCount;
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return;
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}
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CallStack callContext = CallStack();
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// this is sort of a hack around not recording the thread that
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// owns this monitor
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if (chainFront) {
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for (BlockingResourceBase* br = ResourceChainPrev(chainFront);
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br;
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br = ResourceChainPrev(br)) {
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if (br == this) {
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NS_WARNING(
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"Re-entering ReentrantMonitor after acquiring other resources.\n"
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"At calling context\n");
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GetAcquisitionContext().Print(stderr);
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// show the caller why this is potentially bad
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CheckAcquire(callContext);
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PR_EnterMonitor(mReentrantMonitor);
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++mEntryCount;
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return;
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}
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}
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}
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CheckAcquire(callContext);
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PR_EnterMonitor(mReentrantMonitor);
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NS_ASSERTION(0 == mEntryCount, "ReentrantMonitor isn't free!");
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Acquire(callContext); // protected by mReentrantMonitor
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mEntryCount = 1;
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}
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void
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ReentrantMonitor::Exit()
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{
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if (0 == --mEntryCount)
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Release(); // protected by mReentrantMonitor
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PRStatus status = PR_ExitMonitor(mReentrantMonitor);
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NS_ASSERTION(PR_SUCCESS == status, "bad ReentrantMonitor::Exit()");
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}
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nsresult
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ReentrantMonitor::Wait(PRIntervalTime interval)
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{
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AssertCurrentThreadIn();
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// save monitor state and reset it to empty
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PRInt32 savedEntryCount = mEntryCount;
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CallStack savedAcquisitionContext = GetAcquisitionContext();
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BlockingResourceBase* savedChainPrev = mChainPrev;
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mEntryCount = 0;
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SetAcquisitionContext(CallStack::kNone);
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mChainPrev = 0;
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// give up the monitor until we're back from Wait()
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nsresult rv =
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PR_Wait(mReentrantMonitor, interval) == PR_SUCCESS ?
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NS_OK : NS_ERROR_FAILURE;
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// restore saved state
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mEntryCount = savedEntryCount;
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SetAcquisitionContext(savedAcquisitionContext);
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mChainPrev = savedChainPrev;
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return rv;
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}
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//
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// Debug implementation of CondVar
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nsresult
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CondVar::Wait(PRIntervalTime interval)
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{
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AssertCurrentThreadOwnsMutex();
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// save mutex state and reset to empty
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CallStack savedAcquisitionContext = mLock->GetAcquisitionContext();
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BlockingResourceBase* savedChainPrev = mLock->mChainPrev;
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mLock->SetAcquisitionContext(CallStack::kNone);
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mLock->mChainPrev = 0;
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// give up mutex until we're back from Wait()
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nsresult rv =
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PR_WaitCondVar(mCvar, interval) == PR_SUCCESS ?
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NS_OK : NS_ERROR_FAILURE;
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// restore saved state
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mLock->SetAcquisitionContext(savedAcquisitionContext);
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mLock->mChainPrev = savedChainPrev;
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return rv;
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}
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#endif // ifdef DEBUG
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} // namespace mozilla
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