From d6674af04cb74a4efd513d938bed8bf7ab2838eb Mon Sep 17 00:00:00 2001 From: Eric Wong Date: Wed, 27 Nov 2019 01:33:33 +0000 Subject: httpd|nntpd: avoid missed signal wakeups Our attempt at using a self-pipe in signal handlers was ineffective, since pure Perl code execution is deferred and Perl doesn't use an internal self-pipe/eventfd. In retrospect, I actually prefer the simplicity of Perl in this regard... We can use sigprocmask() from Perl, so we can introduce signalfd(2) and EVFILT_SIGNAL support on Linux and *BSD-based systems, respectively. These OS primitives allow us to avoid a race where Perl checks for signals right before epoll_wait() or kevent() puts the process to sleep. The (few) systems nowadays without signalfd(2) or IO::KQueue will now see wakeups every second to avoid missed signals. --- lib/PublicInbox/Daemon.pm | 183 +++++++++++++++++++++++----------------------- 1 file changed, 90 insertions(+), 93 deletions(-) (limited to 'lib/PublicInbox/Daemon.pm') diff --git a/lib/PublicInbox/Daemon.pm b/lib/PublicInbox/Daemon.pm index 0e3b95d2..c7a71ba0 100644 --- a/lib/PublicInbox/Daemon.pm +++ b/lib/PublicInbox/Daemon.pm @@ -15,9 +15,11 @@ use Cwd qw/abs_path/; STDOUT->autoflush(1); STDERR->autoflush(1); use PublicInbox::DS qw(now); +use PublicInbox::Syscall qw(SFD_NONBLOCK); require PublicInbox::EvCleanup; require PublicInbox::Listener; require PublicInbox::ParentPipe; +require PublicInbox::Sigfd; my @CMD; my ($set_user, $oldset, $newset); my (@cfg_listen, $stdout, $stderr, $group, $user, $pid_file, $daemonize); @@ -74,12 +76,14 @@ sub accept_tls_opt ($) { { SSL_server => 1, SSL_startHandshake => 0, SSL_reuse_ctx => $ctx }; } +sub sig_setmask { sigprocmask(SIG_SETMASK, @_) or die "sigprocmask: $!" } + sub daemon_prepare ($) { my ($default_listen) = @_; $oldset = POSIX::SigSet->new(); $newset = POSIX::SigSet->new(); $newset->fillset or die "fillset: $!"; - sigprocmask(SIG_SETMASK, $newset, $oldset) or die "sigprocmask: $!"; + sig_setmask($newset, $oldset); @CMD = ($0, @ARGV); my %opts = ( 'l|listen=s' => \@cfg_listen, @@ -252,30 +256,12 @@ sub daemonize () { } } -sub shrink_pipes { - if ($^O eq 'linux') { # 1031: F_SETPIPE_SZ, 4096: page size - fcntl($_, 1031, 4096) for @_; - } -} - -sub worker_quit { +sub worker_quit { # $_[0] = signal name or number (unused) # killing again terminates immediately: exit unless @listeners; $_->close foreach @listeners; # call PublicInbox::DS::close @listeners = (); - - # create a lazy self-pipe which kicks us out of the EventLoop - # so DS::PostEventLoop can fire - if (pipe(my ($r, $w))) { - shrink_pipes($w); - - # shrink_pipes == noop - PublicInbox::ParentPipe->new($r, *shrink_pipes); - close $w; # wake up from the event loop - } else { - warn "E: pipe failed ($!), quit unreliable\n"; - } my $proc_name; my $warn = 0; # drop idle connections and try to quit gracefully @@ -398,7 +384,7 @@ processes when multiple service instances start. @rv } -sub upgrade () { +sub upgrade { # $_[0] = signal name or number (unused) if ($reexec_pid) { warn "upgrade in-progress: $reexec_pid\n"; return; @@ -453,7 +439,7 @@ sub upgrade_aborted ($) { warn $@, "\n" if $@; } -sub reap_children () { +sub reap_children { # $_[0] = 'CHLD' or POSIX::SIGCHLD() while (1) { my $p = waitpid(-1, WNOHANG) or return; if (defined $reexec_pid && $p == $reexec_pid) { @@ -483,60 +469,50 @@ sub unlink_pid_file_safe_ish ($$) { sub master_loop { pipe(my ($p0, $p1)) or die "failed to create parent-pipe: $!"; - pipe(my ($r, $w)) or die "failed to create self-pipe: $!"; - shrink_pipes($w, $p1); - - IO::Handle::blocking($w, 0); + # 1031: F_SETPIPE_SZ, 4096: page size + fcntl($p1, 1031, 4096) if $^O eq 'linux'; my $set_workers = $worker_processes; - my @caught; - my $master_pid = $$; - foreach my $s (qw(HUP CHLD QUIT INT TERM USR1 USR2 TTIN TTOU WINCH)) { - $SIG{$s} = sub { - return if $$ != $master_pid; - push @caught, $s; - syswrite($w, '.'); - }; - } - sigprocmask(SIG_SETMASK, $oldset) or die "sigprocmask: $!"; reopen_logs(); - # main loop my $quit = 0; - while (1) { - while (my $s = shift @caught) { - if ($s eq 'USR1') { - reopen_logs(); - kill_workers($s); - } elsif ($s eq 'USR2') { - upgrade(); - } elsif ($s =~ /\A(?:QUIT|TERM|INT)\z/) { - exit if $quit++; - kill_workers($s); - } elsif ($s eq 'WINCH') { - if (-t STDIN || -t STDOUT || -t STDERR) { - warn -"ignoring SIGWINCH since we are not daemonized\n"; - $SIG{WINCH} = 'IGNORE'; - } else { - $worker_processes = 0; - } - } elsif ($s eq 'HUP') { - $worker_processes = $set_workers; - kill_workers($s); - } elsif ($s eq 'TTIN') { - if ($set_workers > $worker_processes) { - ++$worker_processes; - } else { - $worker_processes = ++$set_workers; - } - } elsif ($s eq 'TTOU') { - if ($set_workers > 0) { - $worker_processes = --$set_workers; - } - } elsif ($s eq 'CHLD') { - reap_children(); + my $ignore_winch; + my $quit_cb = sub { exit if $quit++; kill_workers($_[0]) }; + my $sig = { + USR1 => sub { reopen_logs(); kill_workers($_[0]); }, + USR2 => \&upgrade, + QUIT => $quit_cb, + INT => $quit_cb, + TERM => $quit_cb, + WINCH => sub { + return if $ignore_winch; + if (-t STDIN || -t STDOUT || -t STDERR) { + $ignore_winch = 1; + warn < sub { + $worker_processes = $set_workers; + kill_workers($_[0]); + }, + TTIN => sub { + if ($set_workers > $worker_processes) { + ++$worker_processes; + } else { + $worker_processes = ++$set_workers; + } + }, + TTOU => sub { + $worker_processes = --$set_workers if $set_workers > 0; + }, + CHLD => \&reap_children, + }; + my $sigfd = PublicInbox::Sigfd->new($sig, 0); + local %SIG = (%SIG, %$sig) if !$sigfd; + sig_setmask($oldset) if !$sigfd; + while (1) { # main loop my $n = scalar keys %pids; if ($quit) { exit if $n == 0; @@ -549,22 +525,29 @@ sub master_loop { } $n = $worker_processes; } - sigprocmask(SIG_SETMASK, $newset) or die "sigprocmask: $!"; - foreach my $i ($n..($worker_processes - 1)) { - my $pid = fork; - if (!defined $pid) { - warn "failed to fork worker[$i]: $!\n"; - } elsif ($pid == 0) { - $set_user->() if $set_user; - return $p0; # run normal work code - } else { - warn "PID=$pid is worker[$i]\n"; - $pids{$pid} = $i; + my $want = $worker_processes - 1; + if ($n <= $want) { + sig_setmask($newset) if !$sigfd; + for my $i ($n..$want) { + my $pid = fork; + if (!defined $pid) { + warn "failed to fork worker[$i]: $!\n"; + } elsif ($pid == 0) { + $set_user->() if $set_user; + return $p0; # run normal work code + } else { + warn "PID=$pid is worker[$i]\n"; + $pids{$pid} = $i; + } } + sig_setmask($oldset) if !$sigfd; + } + + if ($sigfd) { # Linux and IO::KQueue users: + $sigfd->wait_once; + } else { # wake up every second + sleep(1); } - sigprocmask(SIG_SETMASK, $oldset) or die "sigprocmask: $!"; - # just wait on signal events here: - sysread($r, my $buf, 8); } exit # never gets here, just for documentation } @@ -606,6 +589,18 @@ sub daemon_loop ($$$$) { $nntpd->{accept_tls} = $v; } } + my $sig = { + HUP => $refresh, + INT => \&worker_quit, + QUIT => \&worker_quit, + TERM => \&worker_quit, + TTIN => 'IGNORE', + TTOU => 'IGNORE', + USR1 => \&reopen_logs, + USR2 => 'IGNORE', + WINCH => 'IGNORE', + CHLD => \&PublicInbox::DS::enqueue_reap, + }; my $parent_pipe; if ($worker_processes > 0) { $refresh->(); # preload by default @@ -614,16 +609,11 @@ sub daemon_loop ($$$$) { } else { reopen_logs(); $set_user->() if $set_user; - $SIG{USR2} = sub { worker_quit() if upgrade() }; + $sig->{USR2} = sub { worker_quit() if upgrade() }; $refresh->(); } $uid = $gid = undef; reopen_logs(); - $SIG{QUIT} = $SIG{INT} = $SIG{TERM} = *worker_quit; - $SIG{USR1} = *reopen_logs; - $SIG{HUP} = $refresh; - $SIG{CHLD} = 'DEFAULT'; - $SIG{$_} = 'IGNORE' for qw(USR2 TTIN TTOU WINCH); @listeners = map {; my $tls_cb = $post_accept{sockname($_)}; @@ -634,7 +624,14 @@ sub daemon_loop ($$$$) { # this calls epoll_create: PublicInbox::Listener->new($_, $tls_cb || $post_accept) } @listeners; - sigprocmask(SIG_SETMASK, $oldset) or die "sigprocmask: $!"; + my $sigfd = PublicInbox::Sigfd->new($sig, SFD_NONBLOCK); + local %SIG = (%SIG, %$sig) if !$sigfd; + if (!$sigfd) { + # wake up every second to accept signals if we don't + # have signalfd or IO::KQueue: + sig_setmask($oldset); + PublicInbox::DS->SetLoopTimeout(1000); + } PublicInbox::DS->EventLoop; $parent_pipe = undef; } -- cgit v1.2.3-24-ge0c7