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From: "Hans dot Boehm at hp dot com" <gcc-bugzilla@gcc.gnu.org>
To: java-prs@gcc.gnu.org
Subject: [Bug libgcj/16662] IllegalMonitorStateException in EventQueue.getNextEvent(): possible hash synchronization bug?
Date: Tue, 10 Aug 2004 18:30:00 -0000	[thread overview]
Message-ID: <20040810183005.10066.qmail@sourceware.org> (raw)
In-Reply-To: <20040721214713.16662.mckinlay@redhat.com>


------- Additional Comments From Hans dot Boehm at hp dot com  2004-08-10 18:30 -------
I managed to get a run with logging to fail. 

I believe the failure scenario is the following:

1) _Jv_MonitorEnter initially sees an address field which is locked.
This causes the (address & ~(HEAVY | REQUEST_CONVERSION) == addr) test to fail.

2) In the meantime another thread unlocks the address field.

3) _Jv_MonitorEnter's compare_and_swap to acquire the LOCKED bit succeeds 
(unexpectedly).

4) The following code assumes incorrectly that the address corresponds to a 
different object and acquires the heavyweight lock.

5) The lightweight lock is still held by another thread.  bad.

I'll post a patch once I've done a bit of testing.

Hans

-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=16662


  parent reply	other threads:[~2004-08-10 18:30 UTC|newest]

Thread overview: 13+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2004-07-21 21:47 [Bug libgcj/16662] New: " mckinlay at redhat dot com
2004-07-26 18:57 ` [Bug libgcj/16662] " mckinlay at redhat dot com
2004-08-05  0:56 ` Hans dot Boehm at hp dot com
2004-08-07  0:43 ` Hans dot Boehm at hp dot com
2004-08-10  0:44 ` Hans dot Boehm at hp dot com
2004-08-10 18:02 ` mckinlay at redhat dot com
2004-08-10 18:30 ` Hans dot Boehm at hp dot com [this message]
2004-08-12 17:56 ` cvs-commit at gcc dot gnu dot org
2004-08-12 18:38 ` pinskia at gcc dot gnu dot org
2004-09-07 21:15 ` cvs-commit at gcc dot gnu dot org
2004-10-06 22:47 ` cvs-commit at gcc dot gnu dot org
2004-12-01  0:32 ` cvs-commit at gcc dot gnu dot org
     [not found] <bug-16662-6651@http.gcc.gnu.org/bugzilla/>
2007-05-15  9:46 ` rob1weld at aol dot com

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