spawn: pi_fork_exec: restore parent sigmask in child

We continue to unblock SIGCHLD unconditionally, but also
any signals not blocked by the parent (wq_worker).

This will allow Ctrl-C (SIGINT) to stop "git clone" and allow
git-clone cleanup to be performed and other long-running
processes when pi_fork_exec supports setpgid(2).  This won't
affect existing daemons on systems with signalfd(2) or
EVFILT_SIGNAL at all, since those run with signals blocked
anyways.

2 files changed, 14 insertions, 18 deletions

diff --git a/lib/PublicInbox/Spawn.pm b/lib/PublicInbox/Spawn.pm
index f7dcb024..bac24dd1 100644
--- a/lib/PublicInbox/Spawn.pm
+++ b/lib/PublicInbox/Spawn.pm
@@ -82,20 +82,20 @@ int pi_fork_exec(SV *redirref, SV *file, SV *cmdref, SV *envref, SV *rlimref,
         const char *filename = SvPV_nolen(file);
         pid_t pid;
         char **argv, **envp;
-        sigset_t set, old, cset;
+        sigset_t set, old;
         int ret, perrnum, cerrnum = 0;
+        int chld_is_member;
 
         AV2C_COPY(argv, cmd);
         AV2C_COPY(envp, env);
 
-        ret = sigfillset(&set);
-        assert(ret == 0 && "BUG calling sigfillset");
-        ret = sigprocmask(SIG_SETMASK, &set, &old);
-        assert(ret == 0 && "BUG calling sigprocmask to block");
-        ret = sigemptyset(&cset);
-        assert(ret == 0 && "BUG calling sigemptyset");
-        ret = sigaddset(&cset, SIGCHLD);
-        assert(ret == 0 && "BUG calling sigaddset for SIGCHLD");
+        if (sigfillset(&set)) return -1;
+        if (sigprocmask(SIG_SETMASK, &set, &old)) return -1;
+        chld_is_member = sigismember(&old, SIGCHLD);
+        if (chld_is_member < 0) return -1;
+        if (chld_is_member > 0)
+                sigdelset(&old, SIGCHLD);
+
         pid = vfork();
         if (pid == 0) {
                 int sig;
@@ -127,15 +127,13 @@ int pi_fork_exec(SV *redirref, SV *file, SV *cmdref, SV *envref, SV *rlimref,
                                 exit_err(&cerrnum);
                 }
 
-                /*
-                 * don't bother unblocking other signals for now, just SIGCHLD.
-                 * we don't want signals to the group taking out a subprocess
-                 */
-                (void)sigprocmask(SIG_UNBLOCK, &cset, NULL);
+                (void)sigprocmask(SIG_SETMASK, &old, NULL);
                 execve(filename, argv, envp);
                 exit_err(&cerrnum);
         }
         perrnum = errno;
+        if (chld_is_member > 0)
+                sigaddset(&old, SIGCHLD);
         ret = sigprocmask(SIG_SETMASK, &old, NULL);
         assert(ret == 0 && "BUG calling sigprocmask to restore");
         if (cerrnum) {
diff --git a/lib/PublicInbox/SpawnPP.pm b/lib/PublicInbox/SpawnPP.pm
index b0ad4da5..f64b95dc 100644
--- a/lib/PublicInbox/SpawnPP.pm
+++ b/lib/PublicInbox/SpawnPP.pm
@@ -37,10 +37,8 @@ sub pi_fork_exec ($$$$$$) {
                         chdir $cd or die "chdir $cd: $!";
                 }
                 $SIG{$_} = 'DEFAULT' for keys %SIG;
-                my $cset = POSIX::SigSet->new();
-                $cset->addset(POSIX::SIGCHLD) or die "can't add SIGCHLD: $!";
-                sigprocmask(SIG_UNBLOCK, $cset) or
-                                        die "can't unblock SIGCHLD: $!";
+                $old->delset(POSIX::SIGCHLD) or die "delset SIGCHLD: $!";
+                sigprocmask(SIG_SETMASK, $old) or die "SETMASK: ~SIGCHLD: $!";
                 if ($ENV{MOD_PERL}) {
                         exec which('env'), '-i', @$env, @$cmd;
                         die "exec env -i ... $cmd->[0] failed: $!\n";