# Copyright (C) 2016-2018 all contributors
# License: AGPL-3.0+
#
# This allows vfork to be used for spawning subprocesses if
# PERL_INLINE_DIRECTORY is explicitly defined in the environment.
# Under Linux, vfork can make a big difference in spawning performance
# as process size increases (fork still needs to mark pages for CoW use).
# Currently, we only use this for code intended for long running
# daemons (inside the PSGI code (-httpd) and -nntpd). The short-lived
# scripts (-mda, -index, -learn, -init) either use IPC::run or standard
# Perl routines.
package PublicInbox::Spawn;
use strict;
use warnings;
use base qw(Exporter);
use Symbol qw(gensym);
use IO::Handle;
use PublicInbox::ProcessPipe;
our @EXPORT_OK = qw/which spawn popen_rd/;
my $vfork_spawn = <<'VFORK_SPAWN';
#include
#include
#include
#include
#include
#include
#define AV_ALLOCA(av, max) alloca((max = (av_len((av)) + 1)) * sizeof(char *))
static void av2c_copy(char **dst, AV *src, I32 max)
{
I32 i;
for (i = 0; i < max; i++) {
SV **sv = av_fetch(src, i, 0);
dst[i] = sv ? SvPV_nolen(*sv) : 0;
}
dst[max] = 0;
}
static void *deconst(const char *s)
{
union { const char *in; void *out; } u;
u.in = s;
return u.out;
}
/* needs to be safe inside a vfork'ed process */
static void xerr(const char *msg)
{
struct iovec iov[3];
const char *err = strerror(errno); /* should be safe in practice */
iov[0].iov_base = deconst(msg);
iov[0].iov_len = strlen(msg);
iov[1].iov_base = deconst(err);
iov[1].iov_len = strlen(err);
iov[2].iov_base = deconst("\n");
iov[2].iov_len = 1;
writev(2, iov, 3);
_exit(1);
}
#define REDIR(var,fd) do { \
if (var != fd && dup2(var, fd) < 0) \
xerr("error redirecting std"#var ": "); \
} while (0)
/*
* unstable internal API. This was easy to implement but does not
* support arbitrary redirects. It'll be updated depending on
* whatever we'll need in the future.
* Be sure to update PublicInbox::SpawnPP if this changes
*/
int public_inbox_fork_exec(int in, int out, int err,
SV *file, SV *cmdref, SV *envref)
{
AV *cmd = (AV *)SvRV(cmdref);
AV *env = (AV *)SvRV(envref);
const char *filename = SvPV_nolen(file);
pid_t pid;
char **argv, **envp;
I32 max;
sigset_t set, old;
int ret, errnum;
argv = AV_ALLOCA(cmd, max);
av2c_copy(argv, cmd, max);
envp = AV_ALLOCA(env, max);
av2c_copy(envp, env, max);
ret = sigfillset(&set);
assert(ret == 0 && "BUG calling sigfillset");
ret = sigprocmask(SIG_SETMASK, &set, &old);
assert(ret == 0 && "BUG calling sigprocmask to block");
pid = vfork();
if (pid == 0) {
int sig;
REDIR(in, 0);
REDIR(out, 1);
REDIR(err, 2);
for (sig = 1; sig < NSIG; sig++)
signal(sig, SIG_DFL); /* ignore errors on signals */
/*
* don't bother unblocking, we don't want signals
* to the group taking out a subprocess
*/
execve(filename, argv, envp);
xerr("execve failed");
}
errnum = errno;
ret = sigprocmask(SIG_SETMASK, &old, NULL);
assert(ret == 0 && "BUG calling sigprocmask to restore");
errno = errnum;
return (int)pid;
}
VFORK_SPAWN
my $inline_dir = $ENV{PERL_INLINE_DIRECTORY};
$vfork_spawn = undef unless defined $inline_dir && -d $inline_dir && -w _;
if (defined $vfork_spawn) {
# Inline 0.64 or later has locking in multi-process env,
# but we support 0.5 on Debian wheezy
use Fcntl qw(:flock);
eval {
my $f = "$inline_dir/.public-inbox.lock";
open my $fh, '>', $f or die "failed to open $f: $!\n";
flock($fh, LOCK_EX) or die "LOCK_EX failed on $f: $!\n";
eval 'use Inline C => $vfork_spawn'; #, BUILD_NOISY => 1';
my $err = $@;
flock($fh, LOCK_UN) or die "LOCK_UN failed on $f: $!\n";
die $err if $err;
};
if ($@) {
warn "Inline::C failed for vfork: $@\n";
$vfork_spawn = undef;
}
}
unless (defined $vfork_spawn) {
require PublicInbox::SpawnPP;
no warnings 'once';
*public_inbox_fork_exec = *PublicInbox::SpawnPP::public_inbox_fork_exec
}
# n.b. we never use absolute paths with this
sub which ($) {
my ($file) = @_;
foreach my $p (split(':', $ENV{PATH})) {
$p .= "/$file";
return $p if -x $p;
}
undef;
}
sub spawn ($;$$) {
my ($cmd, $env, $opts) = @_;
my $f = which($cmd->[0]);
defined $f or die "$cmd->[0]: command not found\n";
my @env;
$opts ||= {};
my %env = $opts->{-env} ? () : %ENV;
if ($env) {
foreach my $k (keys %$env) {
my $v = $env->{$k};
if (defined $v) {
$env{$k} = $v;
} else {
delete $env{$k};
}
}
}
while (my ($k, $v) = each %env) {
push @env, "$k=$v";
}
my $in = $opts->{0} || 0;
my $out = $opts->{1} || 1;
my $err = $opts->{2} || 2;
my $pid = public_inbox_fork_exec($in, $out, $err, $f, $cmd, \@env);
$pid < 0 ? undef : $pid;
}
sub popen_rd {
my ($cmd, $env, $opts) = @_;
pipe(my ($r, $w)) or die "pipe: $!\n";
$opts ||= {};
my $blocking = $opts->{Blocking};
IO::Handle::blocking($r, $blocking) if defined $blocking;
$opts->{1} = fileno($w);
my $pid = spawn($cmd, $env, $opts);
return unless defined $pid;
return ($r, $pid) if wantarray;
my $ret = gensym;
tie *$ret, 'PublicInbox::ProcessPipe', $pid, $r;
$ret;
}
1;