httpd|nntpd: avoid missed signal wakeups

[public-inbox.git] / lib / PublicInbox / Sigfd.pm

diff --git a/lib/PublicInbox/Sigfd.pm b/lib/PublicInbox/Sigfd.pm
new file mode 100644 (file)
index 0000000..ec5d714
--- /dev/null
+++ b/lib/PublicInbox/Sigfd.pm
@@ -0,0 +1,63 @@
+# Copyright (C) 2019 all contributors <meta@public-inbox.org>
+# License: AGPL-3.0+ <https://www.gnu.org/licenses/agpl-3.0.txt>
+package PublicInbox::Sigfd;
+use strict;
+use parent qw(PublicInbox::DS);
+use fields qw(sig); # hashref similar to %SIG, but signal numbers as keys
+use PublicInbox::Syscall qw(signalfd EPOLLIN EPOLLET SFD_NONBLOCK);
+use POSIX ();
+use IO::Handle ();
+
+# returns a coderef to unblock signals if neither signalfd or kqueue
+# are available.
+sub new {
+       my ($class, $sig, $flags) = @_;
+       my $self = fields::new($class);
+       my %signo = map {;
+               my $cb = $sig->{$_};
+               my $num = ($_ eq 'WINCH' && $^O =~ /linux|bsd/i) ? 28 : do {
+                       my $m = "SIG$_";
+                       POSIX->$m;
+               };
+               $num => $cb;
+       } keys %$sig;
+       my $io;
+       my $fd = signalfd(-1, [keys %signo], $flags);
+       if (defined $fd && $fd >= 0) {
+               $io = IO::Handle->new_from_fd($fd, 'r+');
+       } elsif (eval { require PublicInbox::DSKQXS }) {
+               $io = PublicInbox::DSKQXS->signalfd([keys %signo], $flags);
+       } else {
+               return; # wake up every second to check for signals
+       }
+       if ($flags & SFD_NONBLOCK) { # it can go into the event loop
+               $self->SUPER::new($io, EPOLLIN | EPOLLET);
+       } else { # master main loop
+               $self->{sock} = $io;
+       }
+       $self->{sig} = \%signo;
+       $self;
+}
+
+# PublicInbox::Daemon in master main loop (blocking)
+sub wait_once ($) {
+       my ($self) = @_;
+       my $r = sysread($self->{sock}, my $buf, 128 * 64);
+       if (defined($r)) {
+               while (1) {
+                       my $sig = unpack('L', $buf);
+                       my $cb = $self->{sig}->{$sig};
+                       $cb->($sig) if $cb ne 'IGNORE';
+                       return $r if length($buf) == 128;
+                       $buf = substr($buf, 128);
+               }
+       }
+       $r;
+}
+
+# called by PublicInbox::DS in epoll_wait loop
+sub event_step {
+       while (wait_once($_[0])) {} # non-blocking
+}
+
+1;