RFR: 8212826: Make PtrQueue free list lock-free

Thomas Schatzl thomas.schatzl at oracle.com
Wed Jan 16 12:55:41 UTC 2019


Hi,

On Tue, 2019-01-15 at 17:54 -0500, Kim Barrett wrote:
> > On Jan 15, 2019, at 9:13 AM, Thomas Schatzl <
> > thomas.schatzl at oracle.com> wrote:
> > 
> > Hi Kim,
> > 
> > On Wed, 2019-01-09 at 16:48 -0500, Kim Barrett wrote:
> > > CR:
> > > https://bugs.openjdk.java.net/browse/JDK-8212826
> > > 
> > > Webrev:
> > > http://cr.openjdk.java.net/~kbarrett/8212826/open.00/
> > > 
> > 
> > - ptrQueue.cpp:121:
> > 
> > size_zero seems to be unused, and size_one can be avoided
> > completely by using Atomic::inc/dec instead of add/sub which I
> > would prefer.
> > 
> > Even if you kept add/sub, hardcoding (size_t)1 would be less code
> > than the constant declaration as there are not many uses.
> 
> Can’t use inc/dec, because the incremented values are used, and those
> functions don’t return anything.  But it seems that I forgot that
> Erik and I managed to slip in a bit of argument canonicalization
> here, so that an exact type match isn’t required; just using ‘1u’
> works.
> 
> > - test_ptrQueueBufferAllocator.cpp copyright should be "2018,
> > 2019," instead of just 2019.
> 
> Oops.  Fixed.
> 
> > - the gtest adds a small API for testing and comparison should be
> > part of the test. It honestly seems to add nothing to the final
> > test other than adding additional code, particularly because the
> > other variants mentioned in the comment are not there. So I would
> > prefer to flatten the
> > FreeListPtrQueueBufferAllocator/FreeListPtrQueueBufferCompletedList
> > classes.
> 
> Done, with a bit more cleanup.
> 
> > Looks good otherwise.
> 
> Thanks.
> 
> Note that I’ve filed a bug against Solaris Studio for the problem
> with using pointers to data members. I’ll file a JDK RFE to change
> LockFreeStack to the preferred form once the Solaris Studio bug is
> fixed and we’re no longer supporting versions with the bug.
> 
> New webrevs:
> full: http://cr.openjdk.java.net/~kbarrett/8212826/open.01/
> incr: http://cr.openjdk.java.net/~kbarrett/8212826/open.01.inc/
> 

  Thanks. Looks good.

Thomas




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