user/dev discussion of public-inbox itself
 help / color / Atom feed
From: Eric Wong <e@yhbt.net>
To: meta@public-inbox.org
Subject: [PATCH 2/2] t/httpd-unix: reliability for non-signalfd/EVFILT_SIGNAL
Date: Thu, 16 Apr 2020 01:48:38 +0000
Message-ID: <20200416014838.5939-3-e@yhbt.net> (raw)
In-Reply-To: <20200416014838.5939-1-e@yhbt.net>

Perl seems unable to detect a pending signal (`PL_sig_pending' flag)
even in a sleep(1) loop which wakes up every second.

The (SIGTTOU|SIGUSR2|SIGQUIT) signal itself in the
`PL_psig_pend[sig]' array is not lost, so we can send SIGCHLD
to the process to force the `PL_sig_pending' into being set,
again.

I tested this commit in a loop with the following patch on a
Debian GNU/Linux system to disable signalfd use:

	diff --git a/lib/PublicInbox/Sigfd.pm b/lib/PublicInbox/Sigfd.pm
	index f500902e..597b40d1 100644
	--- a/lib/PublicInbox/Sigfd.pm
	+++ b/lib/PublicInbox/Sigfd.pm
	@@ -12,6 +12,7 @@ use IO::Handle ();
	 # are available.
	 sub new {
		my ($class, $sig, $flags) = @_;
	+	return;
		my $self = fields::new($class);
		my %signo = map {;
			my $cb = $sig->{$_};
---
 t/httpd-unix.t | 24 +++++++++++++++++++++---
 1 file changed, 21 insertions(+), 3 deletions(-)

diff --git a/t/httpd-unix.t b/t/httpd-unix.t
index 7ebc3464..3bfded0c 100644
--- a/t/httpd-unix.t
+++ b/t/httpd-unix.t
@@ -81,13 +81,27 @@ check_sock($unix);
 	ok(-S $unix, 'unix socket still exists');
 }
 
+# Perl can delay signal dispatches due to races, so we repeatedly
+# poke a process with an innocuous signal (SIGCHLD) when signalfd(2)
+# (or EVFILT_SIGNAL) is missing
+my $sig_poke;
+if (my $sigfd = PublicInbox::Sigfd->new({}, 0)) {
+	$sig_poke = sub {}; # noop, we've got signalfd or EVFILT_SIGNAL
+} else {
+	$sig_poke = sub {
+		my $pid = shift;
+		kill('CHLD', $pid);
+	};
+}
+
 sub delay_until {
 	my $cond = shift;
-	for (1..1000) {
+	my $end = time + 30;
+	do {
 		return if $cond->();
 		select undef, undef, undef, 0.012;
-	}
-	Carp::croak('condition failed');
+	} until (time > $end);
+	Carp::confess('condition failed');
 }
 
 SKIP: {
@@ -133,19 +147,23 @@ SKIP: {
 
 	kill('USR2', $pid) or die "USR2 failed: $!";
 	delay_until(sub {
+		$sig_poke->($pid);
 		$pid != (eval { $read_pid->($pid_file) } // $pid)
 	});
 	my $new_pid = $read_pid->($pid_file);
 	isnt($new_pid, $pid, 'new child started');
+	ok($new_pid > 0, '$new_pid valid');
 	delay_until(sub { -s "$pid_file.oldbin" });
 	my $old_pid = $read_pid->("$pid_file.oldbin");
 	is($old_pid, $pid, '.oldbin pid file written');
+	ok($old_pid > 0, '$old_pid valid');
 
 	check_sock($unix); # ensures $new_pid is ready to receive signals
 
 	# first, back out of the upgrade
 	kill('QUIT', $new_pid) or die "kill new PID failed: $!";
 	delay_until(sub {
+		$sig_poke->($new_pid);
 		$pid == (eval { $read_pid->($pid_file) } // 0)
 	});
 	is($read_pid->($pid_file), $pid, 'old PID file restored');

  parent reply index

Thread overview: 4+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-04-16  1:48 [PATCH 0/2] more test fixes Eric Wong
2020-04-16  1:48 ` [PATCH 1/2] t/httpd-corner: improve reliability and diagnostics Eric Wong
2020-04-16  1:48 ` Eric Wong [this message]
2020-04-17  5:22   ` [PATCHv2 2/2] t/httpd-unix: skip some tests w/o signalfd|EVFILT_SIGNAL Eric Wong

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

  List information: http://public-inbox.org/README

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=20200416014838.5939-3-e@yhbt.net \
    --to=e@yhbt.net \
    --cc=meta@public-inbox.org \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link

user/dev discussion of public-inbox itself

Archives are clonable:
	git clone --mirror http://public-inbox.org/meta
	git clone --mirror http://czquwvybam4bgbro.onion/meta
	git clone --mirror http://hjrcffqmbrq6wope.onion/meta
	git clone --mirror http://ou63pmih66umazou.onion/meta

Example config snippet for mirrors

Newsgroups are available over NNTP:
	nntp://news.public-inbox.org/inbox.comp.mail.public-inbox.meta
	nntp://ou63pmih66umazou.onion/inbox.comp.mail.public-inbox.meta
	nntp://czquwvybam4bgbro.onion/inbox.comp.mail.public-inbox.meta
	nntp://hjrcffqmbrq6wope.onion/inbox.comp.mail.public-inbox.meta
	nntp://news.gmane.io/gmane.mail.public-inbox.general

 note: .onion URLs require Tor: https://www.torproject.org/

AGPL code for this site: git clone https://public-inbox.org/public-inbox.git