[PATCH 3/5] send_cmd4: make `tries' a per-call parameter

[Eric Wong <e@80x24.org>]

While existing callers are private (lei, *-index, -watch) are
private, we should not be blocking the event loop in
public-facing servers when we hit ETOOMANYREFS, ENOMEM, or
ENOBUFS.
---
 lib/PublicInbox/CmdIPC4.pm | 12 ++++++------
 lib/PublicInbox/Spawn.pm   | 12 +++++++-----
 lib/PublicInbox/Syscall.pm |  8 ++++----
 3 files changed, 17 insertions(+), 15 deletions(-)

diff --git a/lib/PublicInbox/CmdIPC4.pm b/lib/PublicInbox/CmdIPC4.pm
index 2f102ec6..fc77bd03 100644
--- a/lib/PublicInbox/CmdIPC4.pm
+++ b/lib/PublicInbox/CmdIPC4.pm
@@ -11,8 +11,8 @@ use Socket qw(SOL_SOCKET SCM_RIGHTS);
 sub sendmsg_retry ($) {
 	return 1 if $!{EINTR};
 	return unless ($!{ENOMEM} || $!{ENOBUFS} || $!{ETOOMANYREFS});
-	return if ++$_[0] >= 50;
-	warn "# sleeping on sendmsg: $! (#$_[0])\n";
+	return if --$_[0] < 0;
+	warn "# sleeping on sendmsg: $! ($_[0] tries left)\n";
 	select(undef, undef, undef, 0.1);
 	1;
 }
@@ -22,15 +22,15 @@ require Socket::MsgHdr; # XS
 no warnings 'once';
 
 # any number of FDs per-sendmsg(2) + buffer
-*send_cmd4 = sub ($$$$) { # (sock, fds, buf, flags) = @_;
-	my ($sock, $fds, undef, $flags) = @_;
+*send_cmd4 = sub ($$$$;$) { # (sock, fds, buf, flags) = @_;
+	my ($sock, $fds, undef, $flags, $tries) = @_;
+	$tries //= 50;
 	my $mh = Socket::MsgHdr->new(buf => $_[2]);
 	$mh->cmsghdr(SOL_SOCKET, SCM_RIGHTS, pack('i' x scalar(@$fds), @$fds));
 	my $s;
-	my $try = 0;
 	do {
 		$s = Socket::MsgHdr::sendmsg($sock, $mh, $flags);
-	} while (!defined($s) && sendmsg_retry($try));
+	} while (!defined($s) && sendmsg_retry($tries));
 	$s;
 };
 
diff --git a/lib/PublicInbox/Spawn.pm b/lib/PublicInbox/Spawn.pm
index e36659ce..e9e81e88 100644
--- a/lib/PublicInbox/Spawn.pm
+++ b/lib/PublicInbox/Spawn.pm
@@ -176,15 +176,15 @@ out:
 	return (int)pid;
 }
 
-static int sendmsg_retry(unsigned *tries)
+static int sendmsg_retry(int *tries)
 {
 	const struct timespec req = { 0, 100000000 }; /* 100ms */
 	int err = errno;
 	switch (err) {
 	case EINTR: PERL_ASYNC_CHECK(); return 1;
 	case ENOBUFS: case ENOMEM: case ETOOMANYREFS:
-		if (++*tries >= 50) return 0;
-		fprintf(stderr, "# sleeping on sendmsg: %s (#%u)\n",
+		if (--*tries < 0) return 0;
+		fprintf(stderr, "# sleeping on sendmsg: %s (%d tries left)\n",
 			strerror(err), *tries);
 		nanosleep(&req, NULL);
 		PERL_ASYNC_CHECK();
@@ -201,7 +201,7 @@ union my_cmsg {
 	char pad[sizeof(struct cmsghdr) + 16 + SEND_FD_SPACE];
 };
 
-SV *send_cmd4(PerlIO *s, SV *svfds, SV *data, int flags)
+SV *send_cmd4_(PerlIO *s, SV *svfds, SV *data, int flags, int tries)
 {
 	struct msghdr msg = { 0 };
 	union my_cmsg cmsg = { 0 };
@@ -211,7 +211,6 @@ SV *send_cmd4(PerlIO *s, SV *svfds, SV *data, int flags)
 	AV *fds = (AV *)SvRV(svfds);
 	I32 i, nfds = av_len(fds) + 1;
 	int *fdp;
-	unsigned tries = 0;
 
 	if (SvOK(data)) {
 		iov.iov_base = SvPV(data, dlen);
@@ -332,6 +331,9 @@ EOM
 	if (defined $all_libc) { # set for Gcf2
 		$ENV{PERL_INLINE_DIRECTORY} = $inline_dir;
 		%RLIMITS = rlimit_map();
+		*send_cmd4 = sub ($$$$;$) {
+			send_cmd4_($_[0], $_[1], $_[2], $_[3], 50);
+		}
 	} else {
 		require PublicInbox::SpawnPP;
 		*pi_fork_exec = \&PublicInbox::SpawnPP::pi_fork_exec
diff --git a/lib/PublicInbox/Syscall.pm b/lib/PublicInbox/Syscall.pm
index 99af5bf5..4cbe9623 100644
--- a/lib/PublicInbox/Syscall.pm
+++ b/lib/PublicInbox/Syscall.pm
@@ -467,8 +467,8 @@ if (defined($SYS_sendmsg) && defined($SYS_recvmsg)) {
 no warnings 'once';
 require PublicInbox::CmdIPC4;
 
-*send_cmd4 = sub ($$$$) {
-	my ($sock, $fds, undef, $flags) = @_;
+*send_cmd4 = sub ($$$$;$) {
+	my ($sock, $fds, undef, $flags, $tries) = @_;
 	my $iov = pack('P'.TMPL_size_t,
 			$_[2] // NUL, length($_[2] // NUL) || 1);
 	my $fd_space = scalar(@$fds) * SIZEOF_int;
@@ -487,10 +487,10 @@ require PublicInbox::CmdIPC4;
 			$msg_controllen,
 			0); # msg_flags
 	my $s;
-	my $try = 0;
+	$tries //= 50;
 	do {
 		$s = syscall($SYS_sendmsg, fileno($sock), $mh, $flags);
-	} while ($s < 0 && PublicInbox::CmdIPC4::sendmsg_retry($try));
+	} while ($s < 0 && PublicInbox::CmdIPC4::sendmsg_retry($tries));
 	$s >= 0 ? $s : undef;
 };