libgcj/1124: _Jv_PthreadCheckMonitor test is not portable.

libgcj/1124: _Jv_PthreadCheckMonitor test is not portable.

[charles.gauthier]

>Number:         1124
>Category:       libgcj
>Synopsis:       _Jv_PthreadCheckMonitor test  is not portable.
>Confidential:   no
>Severity:       critical
>Priority:       medium
>Responsible:    tromey
>State:          closed
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Wed Dec 20 12:06:19 PST 2000
>Closed-Date:    Thu Dec 09 09:10:39 PST 1999
>Last-Modified:  Thu Dec  9 09:16:00 PST 1999
>Originator:     charles.gauthier@iit.nrc.ca
>Release:        unknown-1.0
>Organization:
>Environment:
RTEMS, possibly Solaris
>Description:
On systems that do not support recursive mutexes,
pthread_mutex_trylock should not be expected to return 0 if
the caller already has locked the mutex. Unfortunately, it
may not return EDEADLK either.
>How-To-Repeat:
Startup of any application fails under RTEMS
with a java.lang.IllegalMonitorStateException exception when
calling _Jv_PrepareCompiledClass with the class that contains
the main method. Possibly the same under Solaris.
>Fix:
Partial fix is to check for a return value of EDEADLK and 
take it to mean that the caller already has locked the
mutex. Just return 0 in that case.
>Release-Note:

>Audit-Trail:

Formerly PR libgcj/117


From: Tom Tromey <tromey@cygnus.com>
To: charles.gauthier@iit.nrc.ca
Cc: java-gnats@sourceware.cygnus.com
Subject: Re: libgcj/117: _Jv_PthreadCheckMonitor test  is not portable.
Date: Wed, 8 Dec 1999 18:53:54 -0800 (PST)

 I apparently forgot about the no-recursive-mutexes case when writing
 this code.  Can you try this patch?  I haven't even tried compiling
 it... but if it fails, it at least gives the general idea of what to do.
 
 Index: include/posix-threads.h
 ===================================================================
 RCS file: /cvs/java/libgcj/libjava/include/posix-threads.h,v
 retrieving revision 1.9
 diff -u -r1.9 posix-threads.h
 --- posix-threads.h	1999/11/04 16:45:11	1.9
 +++ posix-threads.h	1999/12/09 02:51:30
 @@ -103,10 +103,13 @@
  inline int
  _Jv_PthreadCheckMonitor (_Jv_Mutex_t *mu)
  {
 -  pthread_mutex_t *pmu = _Jv_PthreadGetMutex (mu);
 +  pthread_mutex_t *pmu;
 +#ifdef HAVE_RECURSIVE_MUTEX
 +  pmu = _Jv_PthreadGetMutex (mu);
    // See if the mutex is locked by this thread.
    if (pthread_mutex_trylock (pmu))
      return 1;
 +
  #if defined (PTHREAD_MUTEX_HAVE_M_COUNT)
    // On Linux we exploit knowledge of the implementation.
    int r = pmu->m_count == 1;
 @@ -117,6 +120,17 @@
  #else
    int r = mu->count == 0;
  #endif
 +
 +#else /* HAVE_RECURSIVE_MUTEX */
 +  // In this case we must lock our structure and then see if this
 +  // thread owns the mutex.
 +  pmu = &mu->mutex;
 +  if (pthread_mutex_lock (pmu))
 +    return 0;
 +
 +  int r = mu->thread == pthread_self () && mu->count == 0;
 +#endif /* HAVE_RECURSIVE_MUTEX */
 +
    pthread_mutex_unlock (pmu);
    return r;
  }

From: tromey@sourceware.cygnus.com
To: java-gnats@sourceware.cygnus.com
Cc:  
Subject: libgcj/117
Date: 9 Dec 1999 16:57:27 -0000

 	* include/posix-threads.h (_Jv_PthreadCheckMonitor): Handle case
 	where no recursive mutexes exist.  Fixes PR libgcj/117.
State-Changed-From-To: open->closed
State-Changed-By: tromey
State-Changed-When: Thu Dec  9 09:10:39 1999
State-Changed-Why:
    I checked in a patch which ought to fix this problem.

From: tromey@cygnus.com
To: charles.gauthier@iit.nrc.ca, java-gnats@sourceware.cygnus.com,
  tromey@cygnus.com
Cc:  
Subject: Re: libgcj/117
Date: 9 Dec 1999 17:10:39 -0000

 Synopsis: _Jv_PthreadCheckMonitor test  is not portable.
 
 State-Changed-From-To: open->closed
 State-Changed-By: tromey
 State-Changed-When: Thu Dec  9 09:10:39 1999
 State-Changed-Why:
     I checked in a patch which ought to fix this problem.
 
 http://sourceware.cygnus.com/cgi-bin/gnatsweb.pl?cmd=view&pr=117&database=java
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