<AWT Dev> Review Request for 8065709: Deadlock in awt/logging apparently introduced by 8019623

Anton V. Tarasov anton.tarasov at oracle.com
Mon Jan 19 14:59:08 UTC 2015

Hi Mikhail,

It seems the problem is not limited to EventQueue only. Even if you solve it for EventQueue, the 
EventQueue ctor may cause a chain of calls where some other AWT class is first accessed and 
initialized. What if it contains the same getLogger() call in a static block?

If you agree with this, then there should be a generic solution for the deadlock.

What comes to my mind is the following. The deadlock happens due to a reverse lock taking order. Can 
we change it?

In LogManager.getUserContext() it seems like the javaAwtAccess lock scope can be narrowed down. 
Namely, we can move the javaAwtAccess.getAppletContext() line out of it. In which case the method 
implementation should be additionally synchronized. For instance, we can use the getAppContextLock 
for the whole body of the method. Is the method implemented somewhere else except the AppContext class?

Will it work from your point of view? (Probably, I didn't take into account all the details.)


On 16.01.2015 17:18, mikhail cherkasov wrote:
> Hi all,
> JBS: https://bugs.openjdk.java.net/browse/JDK-8065709
> Webrev: http://cr.openjdk.java.net/~mcherkas/8065709/webrev.00/
> AppContext creation is guarder by getAppContextLockand, but during AppContext creation
> we also call EventQueue initialization, during EQ initialization logger initialization happens
> it acquires "javaAwtAccess".  if "javaAwtAccess" is acquired by other it can lead to deadlock:
> T1                                                   T2
> start AppContext  creation
>                                                      acquire javaAwtAccess
> acquire getAppContextLock
> init EQ                                         call getAppContext
> init Logger                                   waiting for getAppContextLock
> waiting for javaAwtAccess
> I applied the fix suggested in jbs comments by Petr.
> I replaced eager logger initialization in EQ with lazy, so we won't invoke Logger
> during EQ initialization as result no deadlock.
> Thanks,
> Mikhail.

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