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.

1 files changed, 12 insertions, 14 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) {