RFR (S) 8206471: Race with ConcurrentHashTable deleting items on insert with cleanup thread
david.holmes at oracle.com
Mon Jul 9 01:20:49 UTC 2018
On 7/07/2018 5:41 AM, coleen.phillimore at oracle.com wrote:
> Summary: Only fetch Node::next once and use that result.
> A racing thread could NULL next->next()->next(). The Node itself is
> stable until the write_synchronize() but the pointers may be updated.
> See bug for more detail.
> open webrev at http://cr.openjdk.java.net/~coleenp/8206471.01/webrev
> bug link https://bugs.openjdk.java.net/browse/JDK-8206471
The change looks good.
Could there be a similar race at:
552 bucket->release_assign_node_ptr(rem_n_prev, rem_n->next());
553 rem_n = rem_n->next();
Even if not, it is marginally more performant to only do the
685 aux = aux->next();
makes for 3 load-acquire (and 2 if we take the else at line #675).
982 bucket->release_assign_node_ptr(rem_n_prev, rem_n->next());
983 rem_n = rem_n->next();
> Tested with SymbolTable changes and tests that failed. Also tested with
> mach5 hs-tier1-5 (in progress).
> This is actually Robbin's fix, and my review is that it looks good.
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