Alexander,
all your fixes (including the relevant subset of this one) are included
in 4.3.22. Would be great if you could provide feedback if any deadlocks
or other quirks are left.
Regards,
Klaus
On 12.02.2015 12:42, [email protected] wrote:
Hi Klaus,
you are right, if approved Medium lock order is "from parent to
child", then there is nothing wrong in original VirtualBoxImpl.cpp
code. Thanks a lot!
Regards,
Alexander
12.02.2015 14:22, Klaus Espenlaub пишет:
Hi Alexander,
this patch (the VirtualBoxImpl.cpp part) is loosening up
synchronization a bit too much for my taste. The approved lock order
for Medium instances is "from parent to child", which is why your
MachineImpl.cpp change is a perfect catch (and solution, because the
child lock is held unnecessarily).
The VirtualBoxImpl.cpp part on the other hand uses the correct lock
order, so I'm wondering if you have any evidence that this is
actually solving any deadlock. Not disputing that the code should
still work properly after the change (with a tiny bit less atomicity
which isn't strictly required), but I suspect there was nothing wrong
with it initially. If it played part of a deadlock then it's most
likely the other party where the lock order is wrong. If you're
running a debug build then the lock validator in the runtime is
active and should catch anything fishy (unless it involves event
semapshores as they have no owner).
Feedback appreciated :-)
Klaus
On 30.01.2015 15:50, [email protected] wrote:
Diffs attached
30.01.2015 17:49, [email protected] пишет:
Hello!
We would like to contribute to VirtualBox under MIT license. We
send our changes to fix bug described at
https://www.virtualbox.org/ticket/13789 .
The idea is that functions /Medium::removeRegistry()/ and
/Medium::addRegistry()/ themselves take write locks on mediums, so
we get read lock only for /Medium::getAnyMachineBackref()/ call in
/VirtualBox::unregisterMachine()/ function. Also we release read
lock on medium after we got its parent and before we are going to
iterate through parents in /Machine::detachAllMedia()/ function.
Regards,
Alexander
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