Hi Patricio,
On 18/03/2020 6:14 am, Patricio Chilano wrote:
Hi all,
Please review the following patch:
Bug: https://bugs.openjdk.java.net/browse/JDK-8240902
Webrev: http://cr.openjdk.java.net/~pchilanomate/8240902/v1/webrev/
Calling closeConnection() on an already created/opened connection
includes calls to CloseHandle() on objects that can still be used by
other threads. This can lead to either undefined behavior or, as
detailed in the bug comments, changes of state of unrelated objects.
This was a really great find!
This issue was found while debugging the reason behind some jshell test
failures seen after pushing 8230594. Not as important, but there are
also calls to closeStream() from createStream()/openStream() when
failing to create/open a stream that will return after executing
"CHECK_ERROR(enterMutex(stream, NULL));" without closing the intended
resources. Then, calling closeConnection() could assert if the reason of
the previous failure was that the stream's mutex failed to be
created/opened. These patch aims to address these issues too.
Patch looks good in general. The internal reference count guards
deletion of the internal resources, and is itself safe because never
actually delete the connection. Thanks for adding the comment about this
aspect.
A few items:
Please update copyright year before pushing.
Please align ENTER_CONNECTION/LEAVE_CONNECTION macros the same way as
STREAM_INVARIANT.
170 unsigned int refcount;
171 jint state;
I'm unclear about the use of stream->state and connection->state as
guards - unless accessed under a mutex these would seem to at least need
acquire/release semantics.
Additionally the reads of refcount would also seem to need to some form
of memory synchronization - though the Windows docs for the Interlocked*
API does not show how to simply read such a variable! Though I note that
the RtlFirstEntrySList method for the "Interlocked Singly Linked Lists"
API does state "Access to the list is synchronized on a multiprocessor
system." which suggests a read of such a variable does require some form
of memory synchronization!
413 while (attempts>0) {
spaces around >
If the loop at 413 never encounters a zero reference_count then it
doesn't close the events or the mutex but still returns SYS_OK. That
seems wrong but I'm not sure what the right behaviour is here.
And please wait for serviceability folk to review this.
Thanks,
David
-----
Tested in mach5 with the current baseline, tiers1-3 and several runs of
open/test/langtools/:tier1 which includes the jshell tests where this
connector is used. I also applied patch
http://cr.openjdk.java.net/~pchilanomate/8240902/triggerbug/webrev
mentioned in the comments of the bug, on top of the baseline and run the
langtool tests with and without this fix. Without the fix running around
30 repetitions already shows failures in tests
jdk/jshell/FailOverExecutionControlTest.java and
jdk/jshell/FailOverExecutionControlHangingLaunchTest.java. With the fix
I run several hundred runs and saw no failures. Let me know if there is
any additional testing I should do.
As a side note, I see there are a couple of open issues related with
jshell failures (8209848) which could be related to this bug and
therefore might be fixed by this patch.
Thanks,
Patricio
