DOCUMENT:Q240955 08-MAY-2002 [winnt] TITLE :Multithreaded Program May Wait Forever on WaitForMultipleObjects PRODUCT :Microsoft Windows NT PROD/VER:winnt:4.0 SP4,4.0 SP5,4.0 SP6 OPER/SYS: KEYWORDS:kbWinNT400PreSP7Fix ====================================================================== ------------------------------------------------------------------------------- The information in this article applies to: - Microsoft Windows NT Server versions 4.0 SP4, 4.0 SP5, 4.0 SP6 - Microsoft Windows NT Workstation versions 4.0 SP4, 4.0 SP5, 4.0 SP6 ------------------------------------------------------------------------------- SYMPTOMS ======== Any multithreaded program may wait forever on a WaitForMultipleObjects call when waiting on multiple mutexes. This behavior occurs when the thread making the API call is already holding one on the mutexes. For example, assume a program with two threads and two mutexes. Thread A owns mutex 1 and thread B owns mutex 2. If thread A calls WaitForMultipleObjects on both mutex 1 and mutex 2 with bWaitAll=TRUE, the call waits for mutex 2 to be released by thread B. However, the call never returns, even after thread B releases mutex 2. CAUSE ===== This behavior occurs because the Windows NT kernel is not handling the WaitForMultipleObjects call correctly for multiple mutexes. RESOLUTION ========== A supported fix is now available from Microsoft, but it is only intended to correct the problem described in this article and should be applied only to systems experiencing this specific problem. To resolve this problem, contact Microsoft Product Support Services to obtain the fix. For a complete list of Microsoft Product Support Services phone numbers and information on support costs, please go to the following address on the World Wide Web: http://support.microsoft.com/default.aspx?scid=fh;EN-US;CNTACTMS NOTE: In special cases, charges that are normally incurred for support calls may be canceled, if a Microsoft Support Professional determines that a specific update will resolve your problem. Normal support costs will apply to additional support questions and issues that do not qualify for the specific update in question. The English-language version of this fix should have the following file attributes or later: Date Time Size File name Platform ---------------------------------------------------------------- 09/01/99 06:11 PM 931,584 Ntoskrnl.exe Intel 09/01/99 06:13 PM 951,680 Ntkrnlmp.exe Intel 09/01/99 06:10 PM 1,381,824 Ntoskrnl.exe Alpha 09/01/99 06:10 PM 1,410,112 Ntkrnlmp.exe Alpha STATUS ====== Microsoft has confirmed this to be a problem in the Microsoft products that are listed at the beginning of this article. Additional query words: ====================================================================== Keywords : kbWinNT400PreSP7Fix Technology : kbWinNTsearch kbWinNTWsearch kbWinNTW400search kbWinNT400search kbWinNTW400sp5 kbWinNTW400sp4 kbWinNTSsearch kbWinNTS400sp6 kbWinNTS400sp5 kbWinNTS400sp4 kbWinNTS400search kbWinNTW400sp6 Version : winnt:4.0 SP4,4.0 SP5,4.0 SP6 Hardware : ALPHA x86 Issue type : kbbug Solution Type : kbfix ============================================================================= THE INFORMATION PROVIDED IN THE MICROSOFT KNOWLEDGE BASE IS PROVIDED "AS IS" WITHOUT WARRANTY OF ANY KIND. MICROSOFT DISCLAIMS ALL WARRANTIES, EITHER EXPRESS OR IMPLIED, INCLUDING THE WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE. IN NO EVENT SHALL MICROSOFT CORPORATION OR ITS SUPPLIERS BE LIABLE FOR ANY DAMAGES WHATSOEVER INCLUDING DIRECT, INDIRECT, INCIDENTAL, CONSEQUENTIAL, LOSS OF BUSINESS PROFITS OR SPECIAL DAMAGES, EVEN IF MICROSOFT CORPORATION OR ITS SUPPLIERS HAVE BEEN ADVISED OF THE POSSIBILITY OF SUCH DAMAGES. SOME STATES DO NOT ALLOW THE EXCLUSION OR LIMITATION OF LIABILITY FOR CONSEQUENTIAL OR INCIDENTAL DAMAGES SO THE FOREGOING LIMITATION MAY NOT APPLY. Copyright Microsoft Corporation 2002.