[PATCH 2/3] ds: cleanup fork + Reset support

[Eric Wong]

We used to have many entries for %Stack, but nowadays it's just
the one used by next_tick, so just replace it a $cur_runq variable.

I'm reducing reliance on hash keys for things with global scope
to ensure typos can be detected (strict||v5.12 forces us to fix
uses of undeclared variables, but they can't detect typos in
hash keys.
---
 lib/PublicInbox/DS.pm | 18 ++++++++----------
 1 file changed, 8 insertions(+), 10 deletions(-)

diff --git a/lib/PublicInbox/DS.pm b/lib/PublicInbox/DS.pm
index e085a010..8f77b6ad 100644
--- a/lib/PublicInbox/DS.pm
+++ b/lib/PublicInbox/DS.pm
@@ -36,11 +36,11 @@ use Errno qw(EAGAIN EINVAL ECHILD);
 use Carp qw(carp croak);
 our @EXPORT_OK = qw(now msg_more awaitpid add_timer add_uniq_timer);
 
-my %Stack;
 my $nextq; # queue for next_tick
 my $reap_armed;
 my $ToClose; # sockets to close when event loop is done
 our ($AWAIT_PIDS, # pid => [ $callback, @args ]
+       $cur_runq, # only set inside next_tick
      %DescriptorMap,             # fd (num) -> PublicInbox::DS object
      $Poller, # global Select, Epoll, DSPoll, or DSKQXS ref
 
@@ -78,14 +78,14 @@ sub Reset {
                %UniqTimer = ();
                @post_loop_do = ();
 
-               # we may be iterating inside one of these on our stack
-               my @q = delete @Stack{keys %Stack};
-               for my $q (@q) { @$q = () }
+               # we may be called from an *atfork_child inside next_tick:
+               @$cur_runq = () if $cur_runq;
                $AWAIT_PIDS = $nextq = $ToClose = undef; # may call ep_del
                $Poller = PublicInbox::Select->new;
-       } while (@Timers || keys(%Stack) || $nextq || $AWAIT_PIDS ||
+       } while (@Timers || $nextq || $AWAIT_PIDS ||
                $ToClose || keys(%DescriptorMap) ||
-               @post_loop_do || keys(%UniqTimer));
+               @post_loop_do || keys(%UniqTimer) ||
+               scalar(@{$cur_runq // []})); # do not vivify cur_runq
 
        $reap_armed = undef;
        $LoopTimeout = -1;  # no timeout by default
@@ -145,10 +145,9 @@ sub _InitPoller () {
 sub now () { clock_gettime(CLOCK_MONOTONIC) }
 
 sub next_tick () {
-       my $q = $nextq or return;
+       local $cur_runq = $nextq or return;
        $nextq = undef;
-       $Stack{cur_runq} = $q;
-       for my $obj (@$q) {
+       for my $obj (@$cur_runq) {
                # avoid "ref" on blessed refs to workaround a Perl 5.16.3 leak:
                # https://rt.perl.org/Public/Bug/Display.html?id=114340
                if (blessed($obj)) {
@@ -157,7 +156,6 @@ sub next_tick () {
                        $obj->();
                }
        }
-       delete $Stack{cur_runq};
 }
 
 # runs timers and returns milliseconds for next one, or next event loop