[openstack-dev] [oslo][concurrency] lockutils lock fairness / starvation

Joshua Harlow harlowja at fastmail.com
Fri May 19 00:25:06 UTC 2017

Chris Friesen wrote:
> On 05/16/2017 10:45 AM, Joshua Harlow wrote:
>> So fyi,
>> If you really want something like this:
>> Just use:
>> http://fasteners.readthedocs.io/en/latest/api/lock.html#fasteners.lock.ReaderWriterLock
>> And always get a write lock.
>> It is a slightly different way of getting those locks (via a context
>> manager)
>> but the implementation underneath is a deque; so fairness should be
>> assured in
>> FIFO order...
> I'm going ahead and doing this. Your docs for fastener don't actually
> say that lock.ReaderWriterLock.write_lock() provides fairness. If you're
> going to ensure that stays true it might make sense to document the fact.

Sounds great, I was starting to but then got busy with other stuff :-P

> Am I correct that fasteners.InterProcessLock is basically as fair as the
> underlying OS-specific lock? (Which should be reasonably fair except for
> process scheduler priority.)

Yup that IMHO would be fair, its just fnctl under the covers (at least 
for linux). Though from what I remember at 
the lock class here seemed a little nicer (though more complex). That 
guy I think was going to propose some kind of merge, but that never 
seemd to appear.

> Chris
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