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Hi again,<br>
<br>
Erik Helin pointed out a potential race in CMS where the
concurrent cycle may be trying to increment the GC id in parallel
with a young collection. This is scary for other reasons as well
but removing the atomic call exposes it. We concluded that the
safe change is to move the call to register_gc_start() in to the
CMS VM operation. This way we get the VM operation synchronization
and can be sure that two threads are never incrementing the GC id
in parallel.<br>
<br>
Updated webrev here:<br>
<a class="moz-txt-link-freetext" href="http://cr.openjdk.java.net/~brutisso/8008382/webrev.01/">http://cr.openjdk.java.net/~brutisso/8008382/webrev.01/</a><br>
<br>
Bengt<br>
<br>
On 2/18/13 2:21 PM, Bengt Rutisson wrote:<br>
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Hi all,<br>
<br>
Could I have a couple of reviews for this change?<br>
<a moz-do-not-send="true" class="moz-txt-link-freetext"
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There is no need to use atomics in create_new_gc_id() since it is
not called by multiple threads in parallel. Also,
Atomic::add(jlong, jlong *) is broken for ARM. <br>
<br>
We should remove the use of Atomic::add in create_new_gc_id() for
now. If we need this to be called by multiple threads in the
future we have to reconsider how this should be done. Either
adding a lock or doing some kind of 32 bit atomic work.<br>
<br>
Thanks,<br>
Bengt<br>
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