Hi Anton,
please check new version:
http://cr.openjdk.java.net/~mcherkas/8065709/webrev.01/src/share/classes/java/awt/EventQueue.java.udiff.html
I applied changes advised by your in offline, the synchronization and
second check for null was removed.
PlatformLogger.getLogger is already synchronized and can be treated as
sync block and second check.
Thanks,
Mikhail.
On 1/19/2015 10:38 PM, Anton Tarasov wrote:
On 19/01/15 19:15, mikhail cherkasov wrote:
On 1/19/2015 5:59 PM, Anton V. Tarasov wrote:
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?
it can, but currently EventQueue doesn't do such things.
I guess that it's nearly impossible to guarantee that AppContext ctor
will never ever call anything containing uninitialized loggers.
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.
it's already done:
http://hg.openjdk.java.net/jdk9/dev/jdk/rev/83f20d8bc13a
Oh, thanks, I didn't read all the discussion the first time. Well, I
see there's another deadlock involving the
sun.util.logging.PlatformLogger class...
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.)
All this tricky synchronizations was done on purpose, I believe it
was done for performance sake.
So I want to make as less changes as possible, it's better to still
miss couple cases then introduce a
new big issue in the last public update. Anyway, this fix plus
http://hg.openjdk.java.net/jdk9/dev/jdk/rev/83f20d8bc13a
should cover all cases, the only possible if EQ ctor will lead to
javaAwtAccess, but it doesn't.
Ok, I'm fine with the fix (it looks harmless). However, I can't say I
like it because it introduses new lock and breaks consistency (in all
the other cases we get loggers directly)...
I'd look for any better solution in an appropriate time slot.
Reagards,
Anton.
Regards,
Anton.
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.
