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From: Eric Wong <e@80x24.org>
To: meta@public-inbox.org
Subject: [PATCH 2/3] input_pipe: improve error handling
Date: Tue, 17 Oct 2023 10:11:05 +0000
Message-Id: <20231017101106.582556-3-e@80x24.org>
In-Reply-To: <20231017101106.582556-1-e@80x24.org>
References: <20231017101106.582556-1-e@80x24.org>
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List-Id: <meta.public-inbox.org>

Ensure the callback is always guarded by `eval' to catch
exceptions and to force a ->close (EPOLL_CTL_DEL).

We also don't want to blindly set O_NONBLOCK on TTYs since their
O_NONBLOCK semantics aren't well-defined by POSIX.  We can also
drop EPOLLET (edge-triggered) use to reduce the need to make
->requeue calls on our end.
---
 lib/PublicInbox/InputPipe.pm | 48 ++++++++++++++++++++++++------------
 1 file changed, 32 insertions(+), 16 deletions(-)

diff --git a/lib/PublicInbox/InputPipe.pm b/lib/PublicInbox/InputPipe.pm
index 60a9f01f..39aefab2 100644
--- a/lib/PublicInbox/InputPipe.pm
+++ b/lib/PublicInbox/InputPipe.pm
@@ -1,35 +1,51 @@
 # Copyright (C) all contributors <meta@public-inbox.org>
 # License: AGPL-3.0+ <https://www.gnu.org/licenses/agpl-3.0.txt>
 
-# for reading pipes and sockets off the DS event loop
+# for reading pipes, sockets, and TTYs off the DS event loop
 package PublicInbox::InputPipe;
 use v5.12;
 use parent qw(PublicInbox::DS);
-use PublicInbox::Syscall qw(EPOLLIN EPOLLET);
+use PublicInbox::Syscall qw(EPOLLIN);
 
 sub consume {
 	my ($in, $cb, @args) = @_;
 	my $self = bless { cb => $cb, args => \@args }, __PACKAGE__;
-	eval { $self->SUPER::new($in, EPOLLIN|EPOLLET) };
-	return $self->requeue if $@; # regular file
-	$in->blocking(0); # pipe or socket
+	eval { $self->SUPER::new($in, EPOLLIN) };
+	if ($@) { # regular file (but not w/ select|IO::Poll backends)
+		$self->{-need_rq} = 1;
+		$self->requeue;
+	} elsif (-p $in || -s _) { # O_NONBLOCK for sockets and pipes
+		$in->blocking(0);
+	} # TODO: tty
+}
+
+sub close {
+	my ($self) = @_;
+	$self->{-need_rq} ? delete($self->{sock}) : $self->SUPER::close
 }
 
 sub event_step {
 	my ($self) = @_;
 	my $r = sysread($self->{sock} // return, my $rbuf, 65536);
-	if ($r) {
-		$self->{cb}->(@{$self->{args}}, $rbuf);
-		return $self->requeue; # may be regular file or pipe
-	}
-	if (defined($r)) { # EOF
-		$self->{cb}->(@{$self->{args}}, '');
-	} elsif ($!{EAGAIN}) {
-		return;
-	} else { # another error
-		$self->{cb}->(@{$self->{args}}, undef)
+	eval {
+		if ($r) {
+			$self->{cb}->(@{$self->{args}}, $rbuf);
+			$self->requeue if $self->{-need_rq};
+		} elsif (defined($r)) { # EOF
+			$self->{cb}->(@{$self->{args}}, '');
+			$self->close
+		} elsif ($!{EAGAIN}) { # rely on EPOLLIN
+		} elsif ($!{EINTR}) { # rely on EPOLLIN for sockets/pipes/tty
+			$self->requeue if $self->{-need_rq};
+		} else { # another error
+			$self->{cb}->(@{$self->{args}}, undef);
+			$self->close;
+		}
+	};
+	if ($@) {
+		warn "E: $@";
+		$self->close;
 	}
-	$self->{sock}->blocking ? delete($self->{sock}) : $self->close
 }
 
 1;