ds: @post_loop_do replaces SetPostLoopCallback

This allows us to avoid repeatedly using memory-intensive
anonymous subs in CodeSearchIdx where the callback is assigned
frequently.  Anonymous subs are known to leak memory in old
Perls (e.g. 5.16.3 in enterprise distros) and still expensive in
newer Perls.  So favor the (\&subroutine, @args) form which
allows us to eliminate anonymous subs going forward.

Only CodeSearchIdx takes advantage of the new API at the moment,
since it's the biggest repeat user of post-loop callback
changes.

Getting rid of the subroutine and relying on a global `our'
variable also has two advantages:

1) Perl warnings can detect typos at compile-time, whereas the
   (now gone) method could only detect errors at run-time.

2) `our' variable assignment can be `local'-ized to a scope

16 files changed, 64 insertions, 68 deletions

diff --git a/lib/PublicInbox/CodeSearchIdx.pm b/lib/PublicInbox/CodeSearchIdx.pm
index 13fe1c28..587f0b81 100644
--- a/lib/PublicInbox/CodeSearchIdx.pm
+++ b/lib/PublicInbox/CodeSearchIdx.pm
@@ -246,12 +246,18 @@ sub run_todo ($) {
         $n;
 }
 
+sub need_reap { # post_loop_do
+        my (undef, $jobs) = @_;
+        scalar(keys(%$LIVE)) > $jobs;
+}
+
 sub cidx_reap ($$) {
         my ($self, $jobs) = @_;
         while (run_todo($self)) {}
-        my $cb = sub { keys(%$LIVE) > $jobs };
-        PublicInbox::DS->SetPostLoopCallback($cb);
-        PublicInbox::DS::event_loop($MY_SIG, $SIGSET) while $cb->();
+        local @PublicInbox::DS::post_loop_do = \(&need_reap, $jobs);
+        while (need_reap(undef, $jobs)) {
+                PublicInbox::DS::event_loop($MY_SIG, $SIGSET);
+        }
         while (!$jobs && run_todo($self)) {}
 }
 
@@ -397,6 +403,11 @@ sub shard_commit { # via wq_io_do
         send($op_p, "shard_done $n", MSG_EOR);
 }
 
+sub consumers_open { # post_loop_do
+        my (undef, $consumers) = @_;
+        scalar(grep { $_->{sock} } values %$consumers);
+}
+
 sub commit_used_shards ($$$) {
         my ($self, $git, $consumers) = @_;
         local $self->{-shard_ok} = {};
@@ -406,9 +417,7 @@ sub commit_used_shards ($$$) {
                 $IDX_SHARDS[$n]->wq_io_do('shard_commit', [ $p->{op_p} ], $n);
                 $consumers->{$n} = $c;
         }
-        PublicInbox::DS->SetPostLoopCallback(sub {
-                scalar(grep { $_->{sock} } values %$consumers);
-        });
+        local @PublicInbox::DS::post_loop_do = (\&consumers_open, $consumers);
         PublicInbox::DS::event_loop($MY_SIG, $SIGSET);
         my $n = grep { ! $self->{-shard_ok}->{$_} } keys %$consumers;
         die "E: $git->{git_dir} $n shards failed" if $n;
@@ -437,9 +446,7 @@ sub index_repo { # cidx_await cb
                 $CONSUMERS{$n} = $c;
         }
         @shard_in = ();
-        PublicInbox::DS->SetPostLoopCallback(sub {
-                scalar(grep { $_->{sock} } values %CONSUMERS);
-        });
+        local @PublicInbox::DS::post_loop_do = (\&consumers_open, \%CONSUMERS);
         PublicInbox::DS::event_loop($MY_SIG, $SIGSET);
         my $n = grep { ! $self->{-shard_ok}->{$_} } keys %CONSUMERS;
         die "E: $git->{git_dir} $n shards failed" if $n;
@@ -523,7 +530,7 @@ sub scan_git_dirs ($) {
         cidx_reap($self, 0);
 }
 
-sub shards_active { # PostLoopCallback
+sub shards_active { # post_loop_do
         scalar(grep { $_->{-cidx_quit} } @IDX_SHARDS);
 }
 
@@ -572,7 +579,7 @@ sub cidx_run { # main entry point
                 $s->wq_close;
         }
 
-        PublicInbox::DS->SetPostLoopCallback(\&shards_active);
+        local @PublicInbox::DS::post_loop_do = (\&shards_active);
         PublicInbox::DS::event_loop($MY_SIG, $SIGSET) if shards_active();
         $self->lock_release(!!$self->{nchange});
 }
diff --git a/lib/PublicInbox/DS.pm b/lib/PublicInbox/DS.pm
index b6eaf2d7..340086fc 100644
--- a/lib/PublicInbox/DS.pm
+++ b/lib/PublicInbox/DS.pm
@@ -44,7 +44,7 @@ our (
      $Epoll,                     # Global epoll fd (or DSKQXS ref)
      $ep_io,                     # IO::Handle for Epoll
 
-     $PostLoopCallback,          # subref to call at the end of each loop, if defined (global)
+     @post_loop_do,              # subref + args to call at the end of each loop
 
      $LoopTimeout,               # timeout of event loop in milliseconds
      @Timers,                    # timers
@@ -69,7 +69,7 @@ sub Reset {
                 %DescriptorMap = ();
                 @Timers = ();
                 %UniqTimer = ();
-                $PostLoopCallback = undef;
+                @post_loop_do = ();
 
                 # we may be iterating inside one of these on our stack
                 my @q = delete @Stack{keys %Stack};
@@ -79,7 +79,7 @@ sub Reset {
                 $Epoll = undef; # may call DSKQXS::DESTROY
         } while (@Timers || keys(%Stack) || $nextq || $AWAIT_PIDS ||
                 $ToClose || keys(%DescriptorMap) ||
-                $PostLoopCallback || keys(%UniqTimer));
+                @post_loop_do || keys(%UniqTimer));
 
         $reap_armed = undef;
         $LoopTimeout = -1;  # no timeout by default
@@ -247,11 +247,13 @@ sub PostEventLoop () {
         }
 
         # by default we keep running, unless a postloop callback cancels it
-        $PostLoopCallback ? $PostLoopCallback->(\%DescriptorMap) : 1;
+        @post_loop_do ?  $post_loop_do[0]->(\%DescriptorMap,
+                                        @post_loop_do[1..$#post_loop_do])
+                        : 1
 }
 
 # Start processing IO events. In most daemon programs this never exits. See
-# C<PostLoopCallback> for how to exit the loop.
+# C<post_loop_do> for how to exit the loop.
 sub event_loop (;$$) {
         my ($sig, $oldset) = @_;
         $Epoll //= _InitPoller();
@@ -287,24 +289,6 @@ sub event_loop (;$$) {
         } while (PostEventLoop());
 }
 
-=head2 C<< CLASS->SetPostLoopCallback( CODEREF ) >>
-
-Sets post loop callback function.  Pass a subref and it will be
-called every time the event loop finishes.
-
-Return 1 (or any true value) from the sub to make the loop continue, 0 or false
-and it will exit.
-
-The callback function will be passed two parameters: \%DescriptorMap
-
-=cut
-sub SetPostLoopCallback {
-    my ($class, $ref) = @_;
-
-    # global callback
-    $PostLoopCallback = (defined $ref && ref $ref eq 'CODE') ? $ref : undef;
-}
-
 #####################################################################
 ### PublicInbox::DS-the-object code
 #####################################################################
diff --git a/lib/PublicInbox/Daemon.pm b/lib/PublicInbox/Daemon.pm
index 17e799ca..6152a5d3 100644
--- a/lib/PublicInbox/Daemon.pm
+++ b/lib/PublicInbox/Daemon.pm
@@ -350,7 +350,7 @@ sub worker_quit { # $_[0] = signal name or number (unused)
         my $proc_name;
         my $warn = 0;
         # drop idle connections and try to quit gracefully
-        PublicInbox::DS->SetPostLoopCallback(sub {
+        @PublicInbox::DS::post_loop_do = (sub {
                 my ($dmap, undef) = @_;
                 my $n = 0;
                 my $now = now();
diff --git a/lib/PublicInbox/ExtSearchIdx.pm b/lib/PublicInbox/ExtSearchIdx.pm
index 401b18d0..5445b156 100644
--- a/lib/PublicInbox/ExtSearchIdx.pm
+++ b/lib/PublicInbox/ExtSearchIdx.pm
@@ -1388,7 +1388,7 @@ sub eidx_watch { # public-inbox-extindex --watch main loop
         my $quit = PublicInbox::SearchIdx::quit_cb($sync);
         $sig->{QUIT} = $sig->{INT} = $sig->{TERM} = $quit;
         local $self->{-watch_sync} = $sync; # for ->on_inbox_unlock
-        PublicInbox::DS->SetPostLoopCallback(sub { !$sync->{quit} });
+        local @PublicInbox::DS::post_loop_do = (sub { !$sync->{quit} });
         $pr->("initial scan complete, entering event loop\n") if $pr;
         # calls InboxIdle->event_step:
         PublicInbox::DS::event_loop($sig, $oldset);
diff --git a/lib/PublicInbox/IPC.pm b/lib/PublicInbox/IPC.pm
index 730f2cf6..da534aa7 100644
--- a/lib/PublicInbox/IPC.pm
+++ b/lib/PublicInbox/IPC.pm
@@ -245,11 +245,16 @@ sub recv_and_run {
         $n;
 }
 
+sub sock_defined {
+        my (undef, $wqw) = @_;
+        defined($wqw->{sock});
+}
+
 sub wq_worker_loop ($$) {
         my ($self, $bcast2) = @_;
         my $wqw = PublicInbox::WQWorker->new($self, $self->{-wq_s2});
         PublicInbox::WQWorker->new($self, $bcast2) if $bcast2;
-        PublicInbox::DS->SetPostLoopCallback(sub { $wqw->{sock} });
+        local @PublicInbox::DS::post_loop_do = (\&sock_defined, $wqw);
         PublicInbox::DS::event_loop();
         PublicInbox::DS->Reset;
 }
diff --git a/lib/PublicInbox/LEI.pm b/lib/PublicInbox/LEI.pm
index b83de91d..eb9799f6 100644
--- a/lib/PublicInbox/LEI.pm
+++ b/lib/PublicInbox/LEI.pm
@@ -1325,11 +1325,11 @@ sub lazy_start {
         };
         require PublicInbox::DirIdle;
         local $dir_idle = PublicInbox::DirIdle->new(sub {
-                # just rely on wakeup to hit PostLoopCallback set below
+                # just rely on wakeup to hit post_loop_do
                 dir_idle_handler($_[0]) if $_[0]->fullname ne $path;
         });
         $dir_idle->add_watches([$sock_dir]);
-        PublicInbox::DS->SetPostLoopCallback(sub {
+        local @PublicInbox::DS::post_loop_do = (sub {
                 my ($dmap, undef) = @_;
                 if (@st = defined($path) ? stat($path) : ()) {
                         if ($dev_ino_expect ne pack('dd', $st[0], $st[1])) {
diff --git a/lib/PublicInbox/Watch.pm b/lib/PublicInbox/Watch.pm
index d9aadf82..8482100c 100644
--- a/lib/PublicInbox/Watch.pm
+++ b/lib/PublicInbox/Watch.pm
@@ -536,7 +536,7 @@ sub watch { # main entry point
                 add_timer(0, \&poll_fetch_fork, $self, $intvl, $uris);
         }
         watch_fs_init($self) if $self->{mdre};
-        PublicInbox::DS->SetPostLoopCallback(sub { !$self->quit_done });
+        local @PublicInbox::DS::post_loop_do = (sub { !$self->quit_done });
         PublicInbox::DS::event_loop($sig, $oldset); # calls ->event_step
         _done_for_now($self);
 }
diff --git a/t/dir_idle.t b/t/dir_idle.t
index 19e54967..50e1dd27 100644
--- a/t/dir_idle.t
+++ b/t/dir_idle.t
@@ -1,7 +1,7 @@
 #!perl -w
-# Copyright (C) 2020-2021 all contributors <meta@public-inbox.org>
+# Copyright (C) all contributors <meta@public-inbox.org>
 # License: AGPL-3.0+ <https://www.gnu.org/licenses/agpl-3.0.txt>
-use v5.10.1; use strict; use PublicInbox::TestCommon;
+use v5.12; use strict; use PublicInbox::TestCommon;
 use PublicInbox::DS qw(now);
 use File::Path qw(make_path);
 use_ok 'PublicInbox::DirIdle';
@@ -13,7 +13,7 @@ my $di = PublicInbox::DirIdle->new($cb);
 $di->add_watches(["$tmpdir/a", "$tmpdir/c"], 1);
 PublicInbox::DS->SetLoopTimeout(1000);
 my $end = 3 + now;
-PublicInbox::DS->SetPostLoopCallback(sub { scalar(@x) == 0 && now < $end });
+local @PublicInbox::DS::post_loop_do = (sub { scalar(@x) == 0 && now < $end });
 tick(0.011);
 rmdir("$tmpdir/a/b") or xbail "rmdir $!";
 PublicInbox::DS::event_loop();
diff --git a/t/ds-leak.t b/t/ds-leak.t
index 4e8d76cd..eaca05b8 100644
--- a/t/ds-leak.t
+++ b/t/ds-leak.t
@@ -1,9 +1,9 @@
-# Copyright (C) 2019-2021 all contributors <meta@public-inbox.org>
+# Copyright (C) all contributors <meta@public-inbox.org>
 # Licensed the same as Danga::Socket (and Perl5)
 # License: GPL-1.0+ or Artistic-1.0-Perl
 #  <https://www.gnu.org/licenses/gpl-1.0.txt>
 #  <https://dev.perl.org/licenses/artistic.html>
-use strict; use v5.10.1; use PublicInbox::TestCommon;
+use v5.12; use PublicInbox::TestCommon;
 use_ok 'PublicInbox::DS';
 
 if ('close-on-exec for epoll and kqueue') {
@@ -12,7 +12,7 @@ if ('close-on-exec for epoll and kqueue') {
         my $evfd_re = qr/(?:kqueue|eventpoll)/i;
 
         PublicInbox::DS->SetLoopTimeout(0);
-        PublicInbox::DS->SetPostLoopCallback(sub { 0 });
+        local @PublicInbox::DS::post_loop_do = (sub { 0 });
 
         # make sure execve closes if we're using fork()
         my ($r, $w);
@@ -55,7 +55,7 @@ SKIP: {
         my $cb = sub {};
         for my $i (0..$n) {
                 PublicInbox::DS->SetLoopTimeout(0);
-                PublicInbox::DS->SetPostLoopCallback($cb);
+                local @PublicInbox::DS::post_loop_do = ($cb);
                 PublicInbox::DS::event_loop();
                 PublicInbox::DS->Reset;
         }
diff --git a/t/imapd.t b/t/imapd.t
index c7dc01a5..0443c7cb 100644
--- a/t/imapd.t
+++ b/t/imapd.t
@@ -457,7 +457,7 @@ SKIP: {
         my $cfg = PublicInbox::Config->new;
         PublicInbox::DS->Reset;
         my $ii = PublicInbox::InboxIdle->new($cfg);
-        my $cb = sub { PublicInbox::DS->SetPostLoopCallback(sub {}) };
+        my $cb = sub { @PublicInbox::DS::post_loop_do = (sub {}) };
         my $obj = bless \$cb, 'PublicInbox::TestCommon::InboxWakeup';
         $cfg->each_inbox(sub { $_[0]->subscribe_unlock('ident', $obj) });
         my $watcherr = "$tmpdir/watcherr";
@@ -476,7 +476,7 @@ SKIP: {
                 'delivered a message for IDLE to kick -watch') or
                 diag "mda error \$?=$?";
         diag 'waiting for IMAP IDLE wakeup';
-        PublicInbox::DS->SetPostLoopCallback(undef);
+        @PublicInbox::DS::post_loop_do = ();
         PublicInbox::DS::event_loop();
         diag 'inbox unlocked on IDLE wakeup';
 
@@ -493,7 +493,7 @@ SKIP: {
                 'delivered a message for -watch PollInterval');
 
         diag 'waiting for PollInterval wakeup';
-        PublicInbox::DS->SetPostLoopCallback(undef);
+        @PublicInbox::DS::post_loop_do = ();
         PublicInbox::DS::event_loop();
         diag 'inbox unlocked (poll)';
         $w->kill;
diff --git a/t/nntpd.t b/t/nntpd.t
index dbbc37b8..ab6876bb 100644
--- a/t/nntpd.t
+++ b/t/nntpd.t
@@ -436,7 +436,7 @@ sub test_watch {
         my $cfg = PublicInbox::Config->new;
         PublicInbox::DS->Reset;
         my $ii = PublicInbox::InboxIdle->new($cfg);
-        my $cb = sub { PublicInbox::DS->SetPostLoopCallback(sub {}) };
+        my $cb = sub { @PublicInbox::DS::post_loop_do = (sub {}) };
         my $obj = bless \$cb, 'PublicInbox::TestCommon::InboxWakeup';
         $cfg->each_inbox(sub { $_[0]->subscribe_unlock('ident', $obj) });
         my $watcherr = "$tmpdir/watcherr";
diff --git a/t/sigfd.t b/t/sigfd.t
index 7eb6b222..8fc8206c 100644
--- a/t/sigfd.t
+++ b/t/sigfd.t
@@ -1,5 +1,6 @@
-# Copyright (C) 2019-2021 all contributors <meta@public-inbox.org>
-use strict;
+#!perl -w
+# Copyright (C) all contributors <meta@public-inbox.org>
+use v5.12;
 use Test::More;
 use IO::Handle;
 use POSIX qw(:signal_h);
@@ -46,7 +47,7 @@ SKIP: {
                 is($nbsig->wait_once, undef, 'nonblocking ->wait_once');
                 ok($! == Errno::EAGAIN, 'got EAGAIN');
                 kill('HUP', $$) or die "kill $!";
-                PublicInbox::DS->SetPostLoopCallback(sub {}); # loop once
+                local @PublicInbox::DS::post_loop_do = (sub {}); # loop once
                 PublicInbox::DS::event_loop();
                 is($hit->{HUP}->{sigfd}, 2, 'HUP sigfd fired in event loop') or
                         diag explain($hit); # sometimes fails on FreeBSD 11.x
diff --git a/t/watch_maildir.t b/t/watch_maildir.t
index e0719f54..04a1c959 100644
--- a/t/watch_maildir.t
+++ b/t/watch_maildir.t
@@ -1,7 +1,7 @@
-# Copyright (C) 2016-2021 all contributors <meta@public-inbox.org>
+#!perl -w
+# Copyright (C) all contributors <meta@public-inbox.org>
 # License: AGPL-3.0+ <https://www.gnu.org/licenses/agpl-3.0.txt>
-use strict;
-use Test::More;
+use v5.12;
 use PublicInbox::Eml;
 use Cwd;
 use PublicInbox::Config;
@@ -170,7 +170,7 @@ More majordomo info at  http://vger.kernel.org/majordomo-info.html\n);
         my $ii = PublicInbox::InboxIdle->new($cfg);
         my $obj = bless \$cb, 'PublicInbox::TestCommon::InboxWakeup';
         $cfg->each_inbox(sub { $_[0]->subscribe_unlock('ident', $obj) });
-        PublicInbox::DS->SetPostLoopCallback(sub { $delivered == 0 });
+        local @PublicInbox::DS::post_loop_do = (sub { $delivered == 0 });
 
         # wait for -watch to setup inotify watches
         my $sleep = 1;
diff --git a/xt/mem-imapd-tls.t b/xt/mem-imapd-tls.t
index 75f2911f..00199a9b 100644
--- a/xt/mem-imapd-tls.t
+++ b/xt/mem-imapd-tls.t
@@ -82,7 +82,7 @@ sub once { 0 }; # stops event loop
 # setup the event loop so that it exits at every step
 # while we're still doing connect(2)
 PublicInbox::DS->SetLoopTimeout(0);
-PublicInbox::DS->SetPostLoopCallback(\&once);
+local @PublicInbox::DS::post_loop_do = (\&once);
 my $pid = $td->{pid};
 if ($^O eq 'linux' && open(my $f, '<', "/proc/$pid/status")) {
         diag(grep(/RssAnon/, <$f>));
@@ -101,14 +101,13 @@ foreach my $n (1..$nfd) {
         if (!($n % 128) && $DONE != $n) {
                 diag("nr: ($n) $DONE/$nfd");
                 PublicInbox::DS->SetLoopTimeout(-1);
-                PublicInbox::DS->SetPostLoopCallback(sub { $DONE != $n });
+                local @PublicInbox::DS::post_loop_do = (sub { $DONE != $n });
 
                 # clear the backlog:
                 PublicInbox::DS::event_loop();
 
                 # resume looping
                 PublicInbox::DS->SetLoopTimeout(0);
-                PublicInbox::DS->SetPostLoopCallback(\&once);
         }
 }
 
@@ -116,7 +115,7 @@ foreach my $n (1..$nfd) {
 diag "done?: @".time." $DONE/$nfd";
 if ($DONE != $nfd) {
         PublicInbox::DS->SetLoopTimeout(-1);
-        PublicInbox::DS->SetPostLoopCallback(sub { $DONE != $nfd });
+        local @PublicInbox::DS::post_loop_do = (sub { $DONE != $nfd });
         PublicInbox::DS::event_loop();
 }
 is($nfd, $DONE, "$nfd/$DONE done");
diff --git a/xt/mem-nntpd-tls.t b/xt/mem-nntpd-tls.t
index 6e34d233..a861e318 100644
--- a/xt/mem-nntpd-tls.t
+++ b/xt/mem-nntpd-tls.t
@@ -105,7 +105,7 @@ sub once { 0 }; # stops event loop
 # setup the event loop so that it exits at every step
 # while we're still doing connect(2)
 PublicInbox::DS->SetLoopTimeout(0);
-PublicInbox::DS->SetPostLoopCallback(\&once);
+local @PublicInbox::DS::post_loop_do = (\&once);
 
 foreach my $n (1..$nfd) {
         my $io = tcp_connect($nntps, Blocking => 0);
@@ -120,14 +120,14 @@ foreach my $n (1..$nfd) {
         if (!($n % 128) && $n != $DONE) {
                 diag("nr: ($n) $DONE/$nfd");
                 PublicInbox::DS->SetLoopTimeout(-1);
-                PublicInbox::DS->SetPostLoopCallback(sub { $DONE != $n });
+                @PublicInbox::DS::post_loop_do = (sub { $DONE != $n });
 
                 # clear the backlog:
                 PublicInbox::DS::event_loop();
 
                 # resume looping
                 PublicInbox::DS->SetLoopTimeout(0);
-                PublicInbox::DS->SetPostLoopCallback(\&once);
+                @PublicInbox::DS::post_loop_do = (\&once);
         }
 }
 my $pid = $td->{pid};
@@ -141,7 +141,7 @@ $dump_rss->();
 # run the event loop normally, now:
 if ($DONE != $nfd) {
         PublicInbox::DS->SetLoopTimeout(-1);
-        PublicInbox::DS->SetPostLoopCallback(sub {
+        @PublicInbox::DS::post_loop_do = (sub {
                 diag "done: ".time." $DONE";
                 $DONE != $nfd;
         });
diff --git a/xt/net_writer-imap.t b/xt/net_writer-imap.t
index 333e0e3b..f7796e8e 100644
--- a/xt/net_writer-imap.t
+++ b/xt/net_writer-imap.t
@@ -1,5 +1,5 @@
 #!perl -w
-# Copyright (C) 2021 all contributors <meta@public-inbox.org>
+# Copyright (C) all contributors <meta@public-inbox.org>
 # License: AGPL-3.0+ <https://www.gnu.org/licenses/agpl-3.0.txt>
 use strict; use v5.10.1; use PublicInbox::TestCommon;
 use Sys::Hostname qw(hostname);
@@ -233,7 +233,7 @@ EOM
         my $pub_cfg = PublicInbox::Config->new;
         PublicInbox::DS->Reset;
         my $ii = PublicInbox::InboxIdle->new($pub_cfg);
-        my $cb = sub { PublicInbox::DS->SetPostLoopCallback(sub {}) };
+        my $cb = sub { @PublicInbox::DS::post_loop_do = (sub {}) };
         my $obj = bless \$cb, 'PublicInbox::TestCommon::InboxWakeup';
         $pub_cfg->each_inbox(sub { $_[0]->subscribe_unlock('ident', $obj) });
         my $w = start_script(['-watch'], undef, { 2 => $err_wr });