Data races somewhere in SEQUENCE and/or continuation resuming code

[p6rt]

Migrated from rt.perl.org#130796 (status was 'new')

Searchable as RT130796$

[p6rt]

From @zoffixznet

IRC conversation​: https://irclog.perlgeek.de/perl6-dev/2017-02-16#i_14113164

Key excerpts​:

13​:44 IOninja m​: my $c = 0; my @​a = 1, {rand} ... *; my @​b = 1, {rand} ... *; for ^10 -> $i { await start { $ = @​a[^$i] }, start { $ = @​b[^$i] }}; say @​a[^10] eqv @​b[^10]; say $c; say @​a[^10]
13​:44 camelia rakudo-moar a62882​: OUTPUT«True␤0␤((Any) (Any) (Any) (Any) (Any) (Any) (Any) (Any) (Any) (Any))␤»
13​:45 IOninja I don't get why this happens...
13​:47 I'm awaiting both promises on each iteration and they each touch separate arrays with separate seqs

And

13​:52 jnthn m​: my $c = 0; my @​a = lazy gather { take 1; loop { take rand } }; my @​b = lazy gather { take 1; loop { take rand } }; for ^10 -> $i { await start { $ = @​a[^$i] }, start { $ = @​b[^$i] } }; say @​a[^10] eqv @​b[^10]; say $c; say @​a[^10]
13​:52 camelia rakudo-moar 8f53a6​: OUTPUT«False␤0␤(1 0.517685008703888 0.406042977439581 0.0789016444057807 0.825124610951737 0.238677816060427 0.328078729529237 0.284027643066457 0.404746614724066 0.752322767245437)␤»
13​:52 jnthn That works, for example
13​:54 IOninja Seems less busted, but still got it to produce "This continuation has already been invoked" twice​: https://gist.github.com/zoffixznet​/8bcc916ef3e683b8e6cd879a75ab4282
13​:56 gonna ticket it
13​:58 jnthn Ah, then maybe that is where it is...