ds: block signals when reaping

This lets us call dwaitpid long before a process exits
and not have to wait around for it.

This is advantageous for lei where we can run dwaitpid on the
pager as soon as we spawn it, instead of waiting for a client
socket to go away on DESTROY.

1 files changed, 13 insertions, 3 deletions

diff --git a/lib/PublicInbox/DS.pm b/lib/PublicInbox/DS.pm
index 8a560ae8..40994fd4 100644
--- a/lib/PublicInbox/DS.pm
+++ b/lib/PublicInbox/DS.pm
@@ -24,7 +24,7 @@ use strict;
 use v5.10.1;
 use parent qw(Exporter);
 use bytes;
-use POSIX qw(WNOHANG);
+use POSIX qw(WNOHANG sigprocmask SIG_SETMASK);
 use IO::Handle qw();
 use Fcntl qw(SEEK_SET :DEFAULT O_APPEND);
 use Time::HiRes qw(clock_gettime CLOCK_MONOTONIC);
@@ -202,6 +202,16 @@ sub RunTimers {
     ($LoopTimeout < 0 || $LoopTimeout >= $timeout) ? $timeout : $LoopTimeout;
 }
 
+sub sig_setmask { sigprocmask(SIG_SETMASK, @_) or die "sigprocmask: $!" }
+
+sub block_signals () {
+        my $oldset = POSIX::SigSet->new;
+        my $newset = POSIX::SigSet->new;
+        $newset->fillset or die "fillset: $!";
+        sig_setmask($newset, $oldset);
+        $oldset;
+}
+
 # We can't use waitpid(-1) safely here since it can hit ``, system(),
 # and other things.  So we scan the $wait_pids list, which is hopefully
 # not too big.  We keep $wait_pids small by not calling dwaitpid()
@@ -211,6 +221,7 @@ sub reap_pids {
         $reap_armed = undef;
         my $tmp = $wait_pids or return;
         $wait_pids = undef;
+        my $oldset = block_signals();
         foreach my $ary (@$tmp) {
                 my ($pid, $cb, $arg) = @$ary;
                 my $ret = waitpid($pid, WNOHANG);
@@ -225,8 +236,7 @@ sub reap_pids {
                         warn "waitpid($pid, WNOHANG) = $ret, \$!=$!, \$?=$?";
                 }
         }
-        # we may not be done, yet, and could've missed/masked a SIGCHLD:
-        $reap_armed //= requeue(\&reap_pids) if $wait_pids;
+        sig_setmask($oldset);
 }
 
 # reentrant SIGCHLD handler (since reap_pids is not reentrant)