Re: Linux futexes

[Robert Swindells <rjs%fdy2.co.uk@localhost>]

Jason Thorpe <thorpej%me.com@localhost> wrote:
>> On Jul 27, 2019, at 5:05 AM, Robert Swindells <rjs%fdy2.co.uk@localhost> wrote:
>> 
>> I don't think the Linux futex emulation code is correct/good enough.
>
>I have be on/off working on an updated futex implementation written by
>Taylor, with the intent of making it a native call (in order to improve
>or own semaphore and mutex implementations).  You are correct in that
>the current implementation is lacking.
>
>I will try to focus on finishing up the new implementation soon.  But
>even the stuff written by Taylor is a little lacking compared to what
>modern Linux uses futexes for, so some additional work is going to be
>required.

Linux OpenJDK isn't using any extra futex features, it isn't using a
bitmask to selectively wake up threads for example, it just seems to
get into a loop of waking threads up then all of them going back to
sleep.

Robert Swindells