LCOV - code coverage report
Current view: directory - objdir/xpcom/build - BlockingResourceBase.cpp (source / functions) Found Hit Coverage
Test: app.info Lines: 149 85 57.0 %
Date: 2012-06-02 Functions: 13 11 84.6 %

       1                 : /* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4 -*-
       2                 :  * vim: sw=4 ts=4 et :
       3                 :  * ***** BEGIN LICENSE BLOCK *****
       4                 :  * Version: MPL 1.1/GPL 2.0/LGPL 2.1
       5                 :  *
       6                 :  * The contents of this file are subject to the Mozilla Public License Version
       7                 :  * 1.1 (the "License"); you may not use this file except in compliance with
       8                 :  * the License. You may obtain a copy of the License at
       9                 :  * http://www.mozilla.org/MPL/
      10                 :  *
      11                 :  * Software distributed under the License is distributed on an "AS IS" basis,
      12                 :  * WITHOUT WARRANTY OF ANY KIND, either express or implied. See the License
      13                 :  * for the specific language governing rights and limitations under the
      14                 :  * License.
      15                 :  *
      16                 :  * The Original Code is mozilla.org code.
      17                 :  *
      18                 :  * The Initial Developer of the Original Code is
      19                 :  * Netscape Communications Corporation.
      20                 :  * Portions created by the Initial Developer are Copyright (C) 1998
      21                 :  * the Initial Developer. All Rights Reserved.
      22                 :  *
      23                 :  * Contributor(s):
      24                 :  *   Chris Jones <jones.chris.g@gmail.com>
      25                 :  *
      26                 :  * Alternatively, the contents of this file may be used under the terms of
      27                 :  * either of the GNU General Public License Version 2 or later (the "GPL"),
      28                 :  * or the GNU Lesser General Public License Version 2.1 or later (the "LGPL"),
      29                 :  * in which case the provisions of the GPL or the LGPL are applicable instead
      30                 :  * of those above. If you wish to allow use of your version of this file only
      31                 :  * under the terms of either the GPL or the LGPL, and not to allow others to
      32                 :  * use your version of this file under the terms of the MPL, indicate your
      33                 :  * decision by deleting the provisions above and replace them with the notice
      34                 :  * and other provisions required by the GPL or the LGPL. If you do not delete
      35                 :  * the provisions above, a recipient may use your version of this file under
      36                 :  * the terms of any one of the MPL, the GPL or the LGPL.
      37                 :  *
      38                 :  * ***** END LICENSE BLOCK ***** */
      39                 : 
      40                 : #include "mozilla/BlockingResourceBase.h"
      41                 : 
      42                 : #ifdef DEBUG
      43                 : #include "nsAutoPtr.h"
      44                 : 
      45                 : #include "mozilla/CondVar.h"
      46                 : #include "mozilla/ReentrantMonitor.h"
      47                 : #include "mozilla/Mutex.h"
      48                 : #endif // ifdef DEBUG
      49                 : 
      50                 : namespace mozilla {
      51                 : //
      52                 : // BlockingResourceBase implementation
      53                 : //
      54                 : 
      55                 : // static members
      56                 : const char* const BlockingResourceBase::kResourceTypeName[] =
      57                 : {
      58                 :     // needs to be kept in sync with BlockingResourceType
      59                 :     "Mutex", "ReentrantMonitor", "CondVar"
      60                 : };
      61                 : 
      62                 : #ifdef DEBUG
      63                 : 
      64                 : PRCallOnceType BlockingResourceBase::sCallOnce;
      65                 : PRUintn BlockingResourceBase::sResourceAcqnChainFrontTPI = (PRUintn)-1;
      66                 : BlockingResourceBase::DDT* BlockingResourceBase::sDeadlockDetector;
      67                 : 
      68                 : bool
      69               0 : BlockingResourceBase::DeadlockDetectorEntry::Print(
      70                 :     const DDT::ResourceAcquisition& aFirstSeen,
      71                 :     nsACString& out,
      72                 :     bool aPrintFirstSeenCx) const
      73                 : {
      74               0 :     CallStack lastAcquisition = mAcquisitionContext; // RACY, but benign
      75               0 :     bool maybeCurrentlyAcquired = (CallStack::kNone != lastAcquisition);
      76                 :     CallStack printAcquisition =
      77               0 :         (aPrintFirstSeenCx || !maybeCurrentlyAcquired) ?
      78               0 :             aFirstSeen.mCallContext : lastAcquisition;
      79                 : 
      80                 :     fprintf(stderr, "--- %s : %s",
      81               0 :             kResourceTypeName[mType], mName);
      82               0 :     out += BlockingResourceBase::kResourceTypeName[mType];
      83               0 :     out += " : ";
      84               0 :     out += mName;
      85                 : 
      86               0 :     if (maybeCurrentlyAcquired) {
      87               0 :         fputs(" (currently acquired)\n", stderr);
      88               0 :         out += " (currently acquired)\n";
      89                 :     }
      90                 : 
      91               0 :     fputs(" calling context\n", stderr);
      92               0 :     printAcquisition.Print(stderr);
      93                 : 
      94               0 :     return maybeCurrentlyAcquired;
      95                 : }
      96                 : 
      97                 : 
      98          182900 : BlockingResourceBase::BlockingResourceBase(
      99                 :     const char* aName,
     100                 :     BlockingResourceBase::BlockingResourceType aType)
     101                 : {
     102                 :     // PR_CallOnce guaranatees that InitStatics is called in a
     103                 :     // thread-safe way
     104          182900 :     if (PR_SUCCESS != PR_CallOnce(&sCallOnce, InitStatics))
     105               0 :         NS_RUNTIMEABORT("can't initialize blocking resource static members");
     106                 : 
     107          182900 :     mDDEntry = new BlockingResourceBase::DeadlockDetectorEntry(aName, aType);
     108          182900 :     if (!mDDEntry)
     109               0 :         NS_RUNTIMEABORT("can't allocated deadlock detector entry");
     110                 : 
     111          182900 :     mChainPrev = 0;
     112          182900 :     sDeadlockDetector->Add(mDDEntry);
     113          182900 : }
     114                 : 
     115                 : 
     116          182718 : BlockingResourceBase::~BlockingResourceBase()
     117                 : {
     118                 :     // we don't check for really obviously bad things like freeing
     119                 :     // Mutexes while they're still locked.  it is assumed that the
     120                 :     // base class, or its underlying primitive, will check for such
     121                 :     // stupid mistakes.
     122          182718 :     mChainPrev = 0;             // racy only for stupidly buggy client code
     123          182718 :     mDDEntry = 0;               // owned by deadlock detector
     124          182718 : }
     125                 : 
     126                 : 
     127                 : void
     128        24891679 : BlockingResourceBase::CheckAcquire(const CallStack& aCallContext)
     129                 : {
     130        24891679 :     if (eCondVar == mDDEntry->mType) {
     131                 :         NS_NOTYETIMPLEMENTED(
     132               0 :             "FIXME bug 456272: annots. to allow CheckAcquire()ing condvars");
     133               0 :         return;
     134                 :     }
     135                 : 
     136        24891679 :     BlockingResourceBase* chainFront = ResourceChainFront();
     137                 :     nsAutoPtr<DDT::ResourceAcquisitionArray> cycle(
     138                 :         sDeadlockDetector->CheckAcquisition(
     139                 :             chainFront ? chainFront->mDDEntry : 0, mDDEntry,
     140        49784070 :             aCallContext));
     141        24892369 :     if (!cycle)
     142                 :         return;
     143                 : 
     144               0 :     fputs("###!!! ERROR: Potential deadlock detected:\n", stderr);
     145               0 :     nsCAutoString out("Potential deadlock detected:\n");
     146               0 :     bool maybeImminent = PrintCycle(cycle, out);
     147                 : 
     148               0 :     if (maybeImminent) {
     149               0 :         fputs("\n###!!! Deadlock may happen NOW!\n\n", stderr);
     150               0 :         out.Append("\n###!!! Deadlock may happen NOW!\n\n");
     151                 :     } else {
     152                 :         fputs("\nDeadlock may happen for some other execution\n\n",
     153               0 :               stderr);
     154               0 :         out.Append("\nDeadlock may happen for some other execution\n\n");
     155                 :     }
     156                 : 
     157                 :     // XXX can customize behavior on whether we /think/ deadlock is
     158                 :     // XXX about to happen.  for example:
     159                 :     // XXX   if (maybeImminent)
     160                 :     //           NS_RUNTIMEABORT(out.get());
     161               0 :     NS_ERROR(out.get());
     162                 : }
     163                 : 
     164                 : 
     165                 : void
     166        24891743 : BlockingResourceBase::Acquire(const CallStack& aCallContext)
     167                 : {
     168        24891743 :     if (eCondVar == mDDEntry->mType) {
     169                 :         NS_NOTYETIMPLEMENTED(
     170               0 :             "FIXME bug 456272: annots. to allow Acquire()ing condvars");
     171               0 :         return;
     172                 :     }
     173        24891743 :     NS_ASSERTION(mDDEntry->mAcquisitionContext == CallStack::kNone,
     174                 :                  "reacquiring already acquired resource");
     175                 : 
     176        24891522 :     ResourceChainAppend(ResourceChainFront());
     177        24891291 :     mDDEntry->mAcquisitionContext = aCallContext;
     178                 : }
     179                 : 
     180                 : 
     181                 : void
     182        24892007 : BlockingResourceBase::Release()
     183                 : {
     184        24892007 :     if (eCondVar == mDDEntry->mType) {
     185                 :         NS_NOTYETIMPLEMENTED(
     186               0 :             "FIXME bug 456272: annots. to allow Release()ing condvars");
     187               0 :         return;
     188                 :     }
     189                 :       
     190        24892007 :     BlockingResourceBase* chainFront = ResourceChainFront();
     191        24891876 :     NS_ASSERTION(chainFront
     192                 :                  && CallStack::kNone != mDDEntry->mAcquisitionContext,
     193                 :                  "Release()ing something that hasn't been Acquire()ed");
     194                 : 
     195        24891673 :     if (chainFront == this) {
     196        24891673 :         ResourceChainRemove();
     197                 :     }
     198                 :     else {
     199                 :         // not an error, but makes code hard to reason about.
     200               0 :         NS_WARNING("Resource acquired at calling context\n");
     201               0 :         mDDEntry->mAcquisitionContext.Print(stderr);
     202               0 :         NS_WARNING("\nis being released in non-LIFO order; why?");
     203                 :         
     204                 :         // remove this resource from wherever it lives in the chain
     205                 :         // we walk backwards in order of acquisition:
     206                 :         //  (1)  ...node<-prev<-curr...
     207                 :         //              /     /
     208                 :         //  (2)  ...prev<-curr...
     209               0 :         BlockingResourceBase* curr = chainFront;
     210               0 :         BlockingResourceBase* prev = nsnull;
     211               0 :         while (curr && (prev = curr->mChainPrev) && (prev != this))
     212               0 :             curr = prev;
     213               0 :         if (prev == this)
     214               0 :             curr->mChainPrev = prev->mChainPrev;
     215                 :     }
     216                 : 
     217        24891208 :     mDDEntry->mAcquisitionContext = CallStack::kNone;
     218                 : }
     219                 : 
     220                 : 
     221                 : bool
     222               0 : BlockingResourceBase::PrintCycle(const DDT::ResourceAcquisitionArray* aCycle,
     223                 :                                  nsACString& out)
     224                 : {
     225               0 :     NS_ASSERTION(aCycle->Length() > 1, "need > 1 element for cycle!");
     226                 : 
     227               0 :     bool maybeImminent = true;
     228                 : 
     229               0 :     fputs("=== Cyclical dependency starts at\n", stderr);
     230               0 :     out += "Cyclical dependency starts at\n";
     231                 : 
     232               0 :     const DDT::ResourceAcquisition res = aCycle->ElementAt(0);
     233               0 :     maybeImminent &= res.mResource->Print(res, out);
     234                 : 
     235                 :     DDT::ResourceAcquisitionArray::index_type i;
     236               0 :     DDT::ResourceAcquisitionArray::size_type len = aCycle->Length();
     237               0 :     const DDT::ResourceAcquisition* it = 1 + aCycle->Elements();
     238               0 :     for (i = 1; i < len - 1; ++i, ++it) {
     239               0 :         fputs("\n--- Next dependency:\n", stderr);
     240               0 :         out += "\nNext dependency:\n";
     241                 : 
     242               0 :         maybeImminent &= it->mResource->Print(*it, out);
     243                 :     }
     244                 : 
     245               0 :     fputs("\n=== Cycle completed at\n", stderr);
     246               0 :     out += "Cycle completed at\n";
     247               0 :     it->mResource->Print(*it, out, true);
     248                 : 
     249               0 :     return maybeImminent;
     250                 : }
     251                 : 
     252                 : 
     253                 : //
     254                 : // Debug implementation of Mutex
     255                 : void
     256         3400873 : Mutex::Lock()
     257                 : {
     258         3400873 :     CallStack callContext = CallStack();
     259                 : 
     260         3400880 :     CheckAcquire(callContext);
     261         3400901 :     PR_Lock(mLock);
     262         3400899 :     Acquire(callContext);       // protected by mLock
     263         3400882 : }
     264                 : 
     265                 : void
     266         3400874 : Mutex::Unlock()
     267                 : {
     268         3400874 :     Release();                  // protected by mLock
     269         3400843 :     PRStatus status = PR_Unlock(mLock);
     270         3400867 :     NS_ASSERTION(PR_SUCCESS == status, "bad Mutex::Unlock()");
     271         3400867 : }
     272                 : 
     273                 : 
     274                 : //
     275                 : // Debug implementation of ReentrantMonitor
     276                 : void
     277        21773368 : ReentrantMonitor::Enter()
     278                 : {
     279        21773368 :     BlockingResourceBase* chainFront = ResourceChainFront();
     280                 : 
     281                 :     // the code below implements monitor reentrancy semantics
     282                 : 
     283        21773140 :     if (this == chainFront) {
     284                 :         // immediately re-entered the monitor: acceptable
     285          447820 :         PR_EnterMonitor(mReentrantMonitor);
     286          447820 :         ++mEntryCount;
     287          447820 :         return;
     288                 :     }
     289                 : 
     290        21325320 :     CallStack callContext = CallStack();
     291                 :     
     292                 :     // this is sort of a hack around not recording the thread that
     293                 :     // owns this monitor
     294        21325288 :     if (chainFront) {
     295          499782 :         for (BlockingResourceBase* br = ResourceChainPrev(chainFront);
     296                 :              br;
     297                 :              br = ResourceChainPrev(br)) {
     298           42585 :             if (br == this) {
     299                 :                 NS_WARNING(
     300                 :                     "Re-entering ReentrantMonitor after acquiring other resources.\n"
     301               0 :                     "At calling context\n");
     302               0 :                 GetAcquisitionContext().Print(stderr);
     303                 : 
     304                 :                 // show the caller why this is potentially bad
     305               0 :                 CheckAcquire(callContext);
     306                 : 
     307               0 :                 PR_EnterMonitor(mReentrantMonitor);
     308               0 :                 ++mEntryCount;
     309               0 :                 return;
     310                 :             }
     311                 :         }
     312                 :     }
     313                 : 
     314        21325288 :     CheckAcquire(callContext);
     315        21325623 :     PR_EnterMonitor(mReentrantMonitor);
     316        21325612 :     NS_ASSERTION(0 == mEntryCount, "ReentrantMonitor isn't free!");
     317        21325612 :     Acquire(callContext);       // protected by mReentrantMonitor
     318        21325382 :     mEntryCount = 1;
     319                 : }
     320                 : 
     321                 : void
     322        21773328 : ReentrantMonitor::Exit()
     323                 : {
     324        21773328 :     if (0 == --mEntryCount)
     325        21325519 :         Release();              // protected by mReentrantMonitor
     326        21773130 :     PRStatus status = PR_ExitMonitor(mReentrantMonitor);
     327        21773221 :     NS_ASSERTION(PR_SUCCESS == status, "bad ReentrantMonitor::Exit()");
     328        21773221 : }
     329                 : 
     330                 : nsresult
     331           68033 : ReentrantMonitor::Wait(PRIntervalTime interval)
     332                 : {
     333           68033 :     AssertCurrentThreadIn();
     334                 : 
     335                 :     // save monitor state and reset it to empty
     336           68033 :     PRInt32 savedEntryCount = mEntryCount;
     337           68033 :     CallStack savedAcquisitionContext = GetAcquisitionContext();
     338           68033 :     BlockingResourceBase* savedChainPrev = mChainPrev;
     339           68033 :     mEntryCount = 0;
     340           68033 :     SetAcquisitionContext(CallStack::kNone);
     341           68033 :     mChainPrev = 0;
     342                 : 
     343                 :     // give up the monitor until we're back from Wait()
     344                 :     nsresult rv =
     345           68033 :         PR_Wait(mReentrantMonitor, interval) == PR_SUCCESS ?
     346           68033 :             NS_OK : NS_ERROR_FAILURE;
     347                 :     
     348                 :     // restore saved state
     349           68033 :     mEntryCount = savedEntryCount;
     350           68033 :     SetAcquisitionContext(savedAcquisitionContext);
     351           68033 :     mChainPrev = savedChainPrev;
     352                 : 
     353           68033 :     return rv;
     354                 : }
     355                 : 
     356                 : 
     357                 : //
     358                 : // Debug implementation of CondVar
     359                 : nsresult
     360           43838 : CondVar::Wait(PRIntervalTime interval)
     361                 : {
     362           43838 :     AssertCurrentThreadOwnsMutex();
     363                 : 
     364                 :     // save mutex state and reset to empty
     365           43838 :     CallStack savedAcquisitionContext = mLock->GetAcquisitionContext();
     366           43838 :     BlockingResourceBase* savedChainPrev = mLock->mChainPrev;
     367           43838 :     mLock->SetAcquisitionContext(CallStack::kNone);
     368           43838 :     mLock->mChainPrev = 0;
     369                 : 
     370                 :     // give up mutex until we're back from Wait()
     371                 :     nsresult rv =
     372           43838 :         PR_WaitCondVar(mCvar, interval) == PR_SUCCESS ?
     373           43838 :             NS_OK : NS_ERROR_FAILURE;
     374                 : 
     375                 :     // restore saved state
     376           43838 :     mLock->SetAcquisitionContext(savedAcquisitionContext);
     377           43838 :     mLock->mChainPrev = savedChainPrev;
     378                 : 
     379           43838 :     return rv;
     380                 : }
     381                 : 
     382                 : #endif // ifdef DEBUG
     383                 : 
     384                 : 
     385                 : } // namespace mozilla

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