Input Supply.Channel problems

Supply.Channel.txt

So, this would seem to be the way to make a Supply from an IO::Pipe useful for waiting for the
pipe to close and then doing something with the pipe output.  But it does not work reliably.
Similar schemes working directly with the Supply also have issues, since any state accumulating
the output in tap callbacks may not be complete inside a :done callback.  Note that sometimes
(maybe when certain parts of the guts schedule on the same thread) it pretty much works -- I killed
statistically improbable runs with ^C below.  Also note failures on run 8 and run 32 are popular.


$ perl6 -e 'sub f { my $cmd = Proc::Async.new(:path<ls>); my $c = $cmd.stdout.Channel; $cmd.start; $'
after 6 times
  in block <unit> at -e:1

$ perl6 -e 'sub f { my $cmd = Proc::Async.new(:path<ls>); my $c = $cmd.stdout.Channel; $cmd.start; $'
after 8 times
  in block <unit> at -e:1

$ perl6 -e 'sub f { my $cmd = Proc::Async.new(:path<ls>); my $c = $cmd.stdout.Channel; $cmd.start; $'
after 3 times
  in block <unit> at -e:1

$ perl6 -e 'sub f { my $cmd = Proc::Async.new(:path<ls>); my $c = $cmd.stdout.Channel; $cmd.start; $'
after 5 times
  in block <unit> at -e:1

$ perl6 -e 'sub f { my $cmd = Proc::Async.new(:path<ls>); my $c = $cmd.stdout.Channel; $cmd.start; $'

^C
$ perl6 -e 'sub f { my $cmd = Proc::Async.new(:path<ls>); my $c = $cmd.stdout.Channel; $cmd.start; $'
after 32 times
  in block <unit> at -e:1

$ perl6 -e 'sub f { my $cmd = Proc::Async.new(:path<ls>); my $c = $cmd.stdout.Channel; $cmd.start; $'
after 201 times
  in block  at -e:1

$ perl6 -e 'sub f { my $cmd = Proc::Async.new(:path<ls>); my $c = $cmd.stdout.Channel; $cmd.start; $'
after 8 times
  in block <unit> at -e:1

$ perl6 -e 'sub f { my $cmd = Proc::Async.new(:path<ls>); my $c = $cmd.stdout.Channel; $cmd.start; $'
after 8 times
  in block <unit> at -e:1

$ perl6 -e 'sub f { my $cmd = Proc::Async.new(:path<ls>); my $c = $cmd.stdout.Channel; $cmd.start; $'
^C
$ perl6 -e 'sub f { my $cmd = Proc::Async.new(:path<ls>); my $c = $cmd.stdout.Channel; $cmd.start; $'
^C
$ perl6 -e 'sub f { my $cmd = Proc::Async.new(:path<ls>); my $c = $cmd.stdout.Channel; $cmd.start; $'
^C
$ perl6 -e 'sub f { my $cmd = Proc::Async.new(:path<ls>); my $c = $cmd.stdout.Channel; $cmd.start; $'
after 32 times
  in block <unit> at -e:1

$ perl6 -e 'sub f { my $cmd = Proc::Async.new(:path<ls>); my $c = $cmd.stdout.Channel; $cmd.start; $'
after 8 times
  in block <unit> at -e:1

$ perl6 -e 'sub f { my $cmd = Proc::Async.new(:path<ls>); my $c = $cmd.stdout.Channel; $cmd.start; $'
after 145 times
  in block <unit> at -e:1

$ perl6 -e 'sub f { my $cmd = Proc::Async.new(:path<ls>); my $c = $cmd.stdout.Channel; $cmd.start; $'
^C
$ perl6 -e 'sub f { my $cmd = Proc::Async.new(:path<ls>); my $c = $cmd.stdout.Channel; $cmd.start; $'
after 77 times
  in block <unit> at -e:1

$ perl6 -e 'sub f { my $cmd = Proc::Async.new(:path<ls>); my $c = $cmd.stdout.Channel; $cmd.start; $'
after 32 times
  in block <unit> at -e:1

$ perl6 -e 'sub f { my $cmd = Proc::Async.new(:path<ls>); my $c = $cmd.stdout.Channel; $cmd.start; $'
after 32 times
  in block <unit> at -e:1

$ perl6 -e 'sub f { my $cmd = Proc::Async.new(:path<ls>); my $c = $cmd.stdout.Channel; $cmd.start; $'
after 8 times
  in block <unit> at -e:1

$ perl6 -e 'sub f { my $cmd = Proc::Async.new(:path<ls>); my $c = $cmd.stdout.Channel; $cmd.start; $'
after 32 times
  in block <unit> at -e:1

$ perl6 -e 'sub f { my $cmd = Proc::Async.new(:path<ls>); my $c = $cmd.stdout.Channel; $cmd.start; $'
after 1 times
  in block <unit> at -e:1

$ perl6 -e 'sub f { my $cmd = Proc::Async.new(:path<ls>); my $c = $cmd.stdout.Channel; $cmd.start; $'
after 8 times
  in block <unit> at -e:1

$ perl6 -e 'sub f { my $cmd = Proc::Async.new(:path<ls>); my $c = $cmd.stdout.Channel; $cmd.start; $'
after 32 times
  in block <unit> at -e:1

$ perl6 -e 'sub f { my $cmd = Proc::Async.new(:path<ls>); my $c = $cmd.stdout.Channel; $cmd.start; $'
after 8 times
  in block <unit> at -e:1

$ perl6 -e 'sub f { my $cmd = Proc::Async.new(:path<ls>); my $c = $cmd.stdout.Channel; $cmd.start; $'
after 8 times
  in block <unit> at -e:1

$ perl6 -e 'sub f { my $cmd = Proc::Async.new(:path<ls>); my $c = $cmd.stdout.Channel; $cmd.start; $'
after 8 times
  in block <unit> at -e:1

$ perl6 -e 'sub f { my $cmd = Proc::Async.new(:path<ls>); my $c = $cmd.stdout.Channel; $cmd.start; $'
after 8 times
  in block <unit> at -e:1

$ perl6 -e 'sub f { my $cmd = Proc::Async.new(:path<ls>); my $c = $cmd.stdout.Channel; $cmd.start; $'
^C
$