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Alexander,<br>
<br>
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.<br>
<br>
Regards,<br>
Klaus<br>
<div class="moz-cite-prefix">On 12.02.2015 12:42, <a class="moz-txt-link-abbreviated" href="mailto:a.urakov@drweb.com">a.urakov@drweb.com</a>
wrote:<br>
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Hi Klaus,<br>
<br>
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!<br>
<br>
Regards,<br>
Alexander<br>
<br>
<div class="moz-cite-prefix">12.02.2015 14:22, Klaus Espenlaub
пишет:<br>
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Hi Alexander,<br>
<br>
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).<br>
<br>
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).<br>
<br>
Feedback appreciated <span class="moz-smiley-s1"><span> :-) </span></span><br>
<br>
Klaus<br>
<br>
<br>
<div class="moz-cite-prefix">On 30.01.2015 15:50, <a
moz-do-not-send="true" class="moz-txt-link-abbreviated"
href="mailto:a.urakov@drweb.com">a.urakov@drweb.com</a>
wrote:<br>
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Diffs attached<br>
<br>
<div class="moz-cite-prefix">30.01.2015 17:49, <a
moz-do-not-send="true" class="moz-txt-link-abbreviated"
href="mailto:a.urakov@drweb.com">a.urakov@drweb.com</a>
пишет:<br>
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<blockquote cite="mid:54CB99FC.2090805@drweb.com" type="cite">
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Hello!<br>
<br>
We would like to contribute to VirtualBox under MIT license.
We send our changes to fix bug described at <a
moz-do-not-send="true" class="moz-txt-link-freetext"
href="https://www.virtualbox.org/ticket/13789">https://www.virtualbox.org/ticket/13789</a>
.<br>
<br>
The idea is that functions <i>Medium::removeRegistry()</i>
and <i>Medium::addRegistry()</i> themselves take write
locks on mediums, so we get read lock only for <i>Medium::getAnyMachineBackref()</i>
call in <i>VirtualBox::unregisterMachine()</i> function.
Also we release read lock on medium after we got its parent
and before we are going to iterate through parents in <i>Machine::detachAllMedia()</i>
function.<br>
<br>
Regards,<br>
Alexander
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