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From Louis Jacomet <ljaco...@gmail.com>
Subject Re: Race condition in AsyncAppender
Date Mon, 13 Dec 2010 08:22:15 GMT
Hello Curt,

Here is the reference to the created bug:
https://issues.apache.org/bugzilla/show_bug.cgi?id=50463

<https://issues.apache.org/bugzilla/show_bug.cgi?id=50463>Regards,
Louis

On Mon, Dec 13, 2010 at 5:44 AM, Curt Arnold <carnold@apache.org> wrote:

> Thanks for the report and patch.  Creating a new bug would be better.
>  Patch looks good on a first visual check.
>
>
> On Dec 10, 2010, at 3:11 AM, Louis Jacomet wrote:
>
> > Hi all,
> >
> > I recently investigated a deadlock happening inside our JBoss AS.
> > I tracked down the root cause to the AsyncAppender of log4j.
> > We use it in blocking mode, with the default buffer size of 128. I was
> able to reproduce the deadlock live even when increasing the buffer size to
> 512.
> >
> > The problem comes from a race condition when the dispatcher thread dies
> from an exception. When that happens, if the buffer has been filled up by
> other threads doing logging, the thread currently waiting on the buffer to
> be emptied will never be notified and wait there forever.
> > As a category lock is held to access the appender, this lead other
> threads to block forever.
> >
> > I found a bug in the database:
> https://issues.apache.org/bugzilla/show_bug.cgi?id=45915
> > However, the root cause was associated to logging from the Dispatcher
> thread. I have attached a test cause causing the deadlock, showing it can
> occur even when not logging from the dispatcher thread.
> >
> > Should I reopen that bug or create a new one?
> >
> > We are using log4j 1.2.14 and JBoss AS 4.3.0.
> > The latest trunk version of AsyncAppender still suffers from the race
> condition.
> >
> > Regards,
> > Louis
> > <Log4JAsyncAppenderDeadLock.java>
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