- Add timeout-finish support and "down-readiness"

 - LOTS of refactoring to make this work
 - Remove s6-notifywhenup
 - s6-supervise now rocks the casbah
 - rc for 2.2.0.0

15 files changed, 291 insertions, 485 deletions

diff --git a/src/supervision/deps-exe/s6-notifywhenup b/src/supervision/deps-exe/s6-notifywhenup
deleted file mode 100644
index 077e863..0000000
--- a/src/supervision/deps-exe/s6-notifywhenup
+++ /dev/null
@@ -1,3 +0,0 @@
-${LIBS6}
--lskarnet
-${TAINNOW_LIB}
diff --git a/src/supervision/deps-exe/s6-svlisten b/src/supervision/deps-exe/s6-svlisten
index 3bbf778..064975d 100644
--- a/src/supervision/deps-exe/s6-svlisten
+++ b/src/supervision/deps-exe/s6-svlisten
@@ -1,3 +1,5 @@
+s6_svlisten_signal_handler.o
+s6_svlisten_loop.o
 ${LIBS6}
 -lexecline
 -lskarnet
diff --git a/src/supervision/deps-exe/s6-svlisten1 b/src/supervision/deps-exe/s6-svlisten1
index f3a3143..656be3e 100644
--- a/src/supervision/deps-exe/s6-svlisten1
+++ b/src/supervision/deps-exe/s6-svlisten1
@@ -1,3 +1,5 @@
+s6_svlisten_signal_handler.o
+s6_svlisten_loop.o
 ${LIBS6}
 -lskarnet
 ${SOCKET_LIB}
diff --git a/src/supervision/deps-exe/s6-svwait b/src/supervision/deps-exe/s6-svwait
index f3a3143..b71e12f 100644
--- a/src/supervision/deps-exe/s6-svwait
+++ b/src/supervision/deps-exe/s6-svwait
@@ -1,3 +1,4 @@
+s6_svlisten_loop.o
 ${LIBS6}
 -lskarnet
 ${SOCKET_LIB}
diff --git a/src/supervision/s6-notifywhenup.c b/src/supervision/s6-notifywhenup.c
deleted file mode 100644
index 8c45926..0000000
--- a/src/supervision/s6-notifywhenup.c
+++ /dev/null
@@ -1,99 +0,0 @@
-/* ISC license. */
-
-#include <unistd.h>
-#include <errno.h>
-#include <skalibs/uint.h>
-#include <skalibs/bytestr.h>
-#include <skalibs/sgetopt.h>
-#include <skalibs/strerr2.h>
-#include <skalibs/allreadwrite.h>
-#include <skalibs/tai.h>
-#include <skalibs/iopause.h>
-#include <skalibs/djbunix.h>
-#include <s6/ftrigw.h>
-#include <s6/s6-supervise.h>
-
-#define USAGE "s6-notifywhenup [ -d fd ] [ -e fifodir ] [ -f ] [ -X ] [ -t timeout ] prog..."
-#define dieusage() strerr_dieusage(100, USAGE)
-
-static int run_child (int fd, char const *fifodir, unsigned int timeout)
-{
-  char dummy[4096] ;
-  iopause_fd x = { .fd = fd, .events = IOPAUSE_READ } ;
-  tain_t deadline ;
-  char pack[TAIN_PACK] ;
-  if (!tain_now_g()) strerr_diefu1sys(111, "tain_now") ;
-  if (timeout) tain_from_millisecs(&deadline, timeout) ;
-  else deadline = tain_infinite_relative ;
-  tain_add_g(&deadline, &deadline) ;
-  for (;;)
-  {
-    register int r = iopause_g(&x, 1, &deadline) ;
-    if (r < 0) strerr_diefu1sys(111, "iopause") ;
-    if (!r) return 99 ;
-    r = sanitize_read(fd_read(fd, dummy, 4096)) ;
-    if (r < 0)
-      if (errno == EPIPE) return 1 ;
-      else strerr_diefu1sys(111, "read from parent") ;
-    else if (r)
-      if (byte_chr(dummy, r, '\n') < r) break ;
-  }
-  close(fd) ;
-  tain_pack(pack, &STAMP) ;
-  if (!openwritenclose_suffix(S6_SUPERVISE_READY_FILENAME, pack, TAIN_PACK, ".new"))
-    strerr_warnwu1sys("open " S6_SUPERVISE_READY_FILENAME " for writing") ;
-  ftrigw_notify(fifodir, 'U') ;
-  return 0 ;
-}
-
-int main (int argc, char const *const *argv, char const *const *envp)
-{
-  unsigned int fd = 1 ;
-  char const *fifodir = "event" ;
-  int df = 1, fake = 0 ;
-  unsigned int timeout = 0 ;
-  PROG = "s6-notifywhenup" ;
-  {
-    subgetopt_t l = SUBGETOPT_ZERO ;
-    for (;;)
-    {
-      register int opt = subgetopt_r(argc, argv, "Xd:e:ft:", &l) ;
-      if (opt == -1) break ;
-      switch (opt)
-      {
-        case 'X' : fake = 1 ; break ;
-        case 'd' : if (!uint0_scan(l.arg, &fd)) dieusage() ; break ;
-        case 'e' : fifodir = l.arg ; break ;
-        case 'f' : df = 0 ; break ;
-        case 't' : if (!uint0_scan(l.arg, &timeout)) dieusage() ; break ;
-        default : dieusage() ;
-      }
-    }
-    argc -= l.ind ; argv += l.ind ;
-  }
-  if (!argc) dieusage() ;
-  strerr_warnw1x("this program is deprecated. Use a notification-fd file instead.") ;
-
-  {
-    int p[2] ;
-    pid_t pid ;
-    if (pipe(p) < 0) strerr_diefu1sys(111, "pipe") ;
-    pid = df ? doublefork() : fork() ;
-    if (pid < 0) strerr_diefu1sys(111, df ? "doublefork" : "fork") ;
-    else if (!pid)
-    {
-      PROG = "s6-notifywhenup (child)" ;
-      close(p[1]) ;
-      return run_child(p[0], fifodir, timeout) ;
-    }
-    close(p[0]) ;
-    if (fd_move((int)fd, p[1]) < 0) strerr_diefu1sys(111, "fd_move") ;
-  }
-  if (fake)
-  {
-    write(fd, "\n", 1) ;
-    close(fd) ;
-  }
-  pathexec_run(argv[0], argv, envp) ;
-  strerr_dieexec(111, argv[0]) ;
-}
diff --git a/src/supervision/s6-supervise.c b/src/supervision/s6-supervise.c
index 5ce718f..0f0b256 100644
--- a/src/supervision/s6-supervise.c
+++ b/src/supervision/s6-supervise.c
@@ -45,18 +45,11 @@ typedef action_t *action_t_ref ;
 
 static tain_t deadline ;
 static tain_t dontrespawnbefore = TAIN_EPOCH ;
-static s6_svstatus_t status = { .stamp = TAIN_ZERO, .pid = 0, .flagwant = 1, .flagwantup = 1, .flagpaused = 0, .flagfinishing = 0, .wstat = 0 } ;
+static s6_svstatus_t status = S6_SVSTATUS_ZERO ;
 static state_t state = DOWN ;
 static int cont = 1 ;
 static int notifyfd = -1 ;
 
-static inline void down_and_delay (void)
-{
-  state = DOWN ;
-  if (tain_future(&dontrespawnbefore)) deadline = dontrespawnbefore ;
-  else tain_copynow(&deadline) ;
-}
-
 static inline void settimeout (int secs)
 {
   tain_addsec_g(&deadline, secs) ;
@@ -73,6 +66,37 @@ static inline void announce (void)
     strerr_warnwu1sys("write status file") ;
 }
 
+static int read_uint (char const *file, unsigned int *fd)
+{
+  char buf[UINT_FMT + 1] ;
+  register int r = openreadnclose_nb(file, buf, UINT_FMT) ;
+  if (r < 0)
+  {
+    if (errno != ENOENT) strerr_warnwu2sys("open ", file) ;
+    return 0 ;
+  }
+  buf[byte_chr(buf, r, '\n')] = 0 ;
+  if (!uint0_scan(buf, fd))
+  {
+    strerr_warnw2x("invalid ", file) ;
+    return 0 ;
+  }
+  return 1 ;
+}
+
+static void set_down_and_ready (char const *s, unsigned int n)
+{
+  status.pid = 0 ;
+  status.flagfinishing = 0 ;
+  status.flagready = 1 ;
+  tain_copynow(&status.readystamp) ;
+  state = DOWN ;
+  if (tain_future(&dontrespawnbefore)) deadline = dontrespawnbefore ;
+  else tain_copynow(&deadline) ;
+  announce() ;
+  ftrigw_notifyb_nosig(S6_SUPERVISE_EVENTDIR, s, n) ;
+}
+
 
 /* The action array. */
 
@@ -183,27 +207,12 @@ static void trystart (void)
     strerr_warnwu1sys("pipe (waiting 60 seconds)") ;
     return ;
   }
+  if (read_uint("notification-fd", &fd) && pipe(notifyp) < 0)
   {
-    char buf[UINT_FMT + 1] ;
-    register int r = openreadnclose("notification-fd", buf, UINT_FMT) ;
-    if (r < 0)
-    {
-      if (errno != ENOENT)
-        strerr_warnwu1sys("open notification-fd") ;
-    }
-    else
-    {
-      buf[byte_chr(buf, r, '\n')] = 0 ;
-      if (!uint0_scan(buf, &fd))
-        strerr_warnw1x("invalid notification-fd") ;
-      else if (pipe(notifyp) < 0)
-      {
-        settimeout(60) ;
-        strerr_warnwu1sys("pipe (waiting 60 seconds)") ;
-        fd_close(p[1]) ; fd_close(p[0]) ;
-        return ;
-      }
-    }
+    settimeout(60) ;
+    strerr_warnwu1sys("pipe (waiting 60 seconds)") ;
+    fd_close(p[1]) ; fd_close(p[0]) ;
+    return ;
   }
   pid = fork() ;
   if (pid < 0)
@@ -222,8 +231,6 @@ static void trystart (void)
     selfpipe_finish() ;
     if (notifyp[0] >= 0) close(notifyp[0]) ;
     close(p[0]) ;
-    if (unlink(S6_SUPERVISE_READY_FILENAME) < 0 && errno != ENOENT)
-      strerr_warnwu1sys("unlink " S6_SUPERVISE_READY_FILENAME) ;
     if (notifyp[1] >= 0 && fd_move((int)fd, notifyp[1]) < 0)
     {
       failcoe(p[1]) ;
@@ -264,6 +271,7 @@ static void trystart (void)
   settimeout_infinite() ;
   state = UP ;
   status.pid = pid ;
+  status.flagready = 0 ;
   tain_copynow(&status.stamp) ;
   tain_addsec_g(&dontrespawnbefore, 1) ;
   announce() ;
@@ -303,17 +311,25 @@ static void down_d (void)
   announce() ;
 }
 
-static inline void tryfinish (int islast)
+static int uplastup_z (void)
 {
-  register pid_t pid = fork() ;
-  if (pid < 0)
+  status.wstat = (int)status.pid ;
+  status.flagpaused = 0 ;
+  status.flagready = 0 ;
+  tain_copynow(&status.stamp) ;
+  if (notifyfd >= 0)
+  {
+    fd_close(notifyfd) ;
+    notifyfd = -1 ;
+  }
+  status.pid = fork() ;
+  if (status.pid < 0)
   {
     strerr_warnwu2sys("fork for ", "./finish") ;
-    if (islast) bail() ;
-    down_and_delay() ;
-    return ;
+    set_down_and_ready("dD", 2) ;
+    return 0 ;
   }
-  else if (!pid)
+  else if (!status.pid)
   {
     char fmt0[UINT_FMT] ;
     char fmt1[UINT_FMT] ;
@@ -325,39 +341,35 @@ static inline void tryfinish (int islast)
     execve("./finish", cargv, (char *const *)environ) ;
     _exit(127) ;
   }
-  status.pid = pid ;
   status.flagfinishing = 1 ;
-  state = islast ? LASTFINISH : FINISH ;
+  announce() ;
+  ftrigw_notifyb_nosig(S6_SUPERVISE_EVENTDIR, "d", 1) ;
+  {
+    tain_t tto ;
+    unsigned int timeout ;
+    if (!read_uint("timeout-finish", &timeout)) timeout = 5000 ;
+    if (timeout && tain_from_millisecs(&tto, timeout))
+      tain_add_g(&deadline, &tto) ;
+    else settimeout_infinite() ;
+  }
+  return 1 ;
 }
 
-static void uptimeout (void)
+static void up_z (void)
 {
-  settimeout_infinite() ;
-  strerr_warnw1x("can't happen: timeout while the service is up!") ;
+  if (uplastup_z()) state = FINISH ;
 }
 
-static void uplastup_z (int islast)
+static void lastup_z (void)
 {
-  status.wstat = status.pid ;
-  status.pid = 0 ;
-  tain_copynow(&status.stamp) ;
-  if (notifyfd >= 0)
-  {
-    fd_close(notifyfd) ;
-    notifyfd = -1 ;
-  }
-  tryfinish(islast) ;
-  announce() ;
-  ftrigw_notifyb_nosig(S6_SUPERVISE_EVENTDIR, "d", 1) ;
-  if (unlink(S6_SUPERVISE_READY_FILENAME) < 0 && errno != ENOENT)
-    strerr_warnwu1sys("unlink " S6_SUPERVISE_READY_FILENAME) ;
-  settimeout(5) ;
+  if (uplastup_z()) state = LASTFINISH ;
+  else bail() ;
 }
 
-static void up_z (void)
+static void uptimeout (void)
 {
-  status.flagpaused = 0 ;
-  uplastup_z(0) ;
+  settimeout_infinite() ;
+  strerr_warnw1x("can't happen: timeout while the service is up!") ;
 }
 
 static void up_o (void)
@@ -400,17 +412,14 @@ static void up_term (void)
 
 static void finishtimeout (void)
 {
-  strerr_warnw1x("finish script takes too long - killing it") ;
+  strerr_warnw1x("finish script lifetime reached maximum value - sending it a SIGKILL") ;
   killc() ; killk() ;
-  settimeout(3) ;
+  settimeout(5) ;
 }
 
 static void finish_z (void)
 {
-  status.pid = 0 ;
-  status.flagfinishing = 0 ;
-  down_and_delay() ;
-  announce() ;
+  set_down_and_ready("D", 1) ;
 }
 
 static void finish_u (void)
@@ -431,11 +440,6 @@ static void finish_X (void)
   finish_x() ;
 }
 
-static void lastup_z (void)
-{
-  uplastup_z(1) ;
-}
-
 static action_t_ref const actions[5][24] =
 {
   { &downtimeout, &nop, &bail, &bail, &bail,
@@ -470,10 +474,9 @@ static inline void handle_notifyfd (void)
     r = sanitize_read(fd_read(notifyfd, buf, 4096)) ;
     if (r > 0 && byte_chr(buf, r, '\n') < r)
     {
-      char pack[TAIN_PACK] ;
-      tain_pack(pack, &STAMP) ;
-      if (!openwritenclose_suffix(S6_SUPERVISE_READY_FILENAME, pack, TAIN_PACK, ".new"))
-        strerr_warnwu3sys("open ", S6_SUPERVISE_READY_FILENAME, " for writing") ;
+      tain_copynow(&status.readystamp) ;
+      status.flagready = 1 ;
+      announce() ;
       ftrigw_notifyb_nosig(S6_SUPERVISE_EVENTDIR, "U", 1) ;
       r = -1 ;
     }
@@ -504,7 +507,7 @@ static inline void handle_signals (void)
             if (errno != ECHILD) strerr_diefu1sys(111, "wait_pid_nohang") ;
             else break ;
           else if (!r) break ;
-          status.pid = wstat ; /* don't overwrite status.wstat if it's ./finish */
+          status.pid = (pid_t)wstat ; /* don't overwrite status.wstat if it's ./finish */
           (*actions[state][V_CHLD])() ;
         }
         break ;
diff --git a/src/supervision/s6-svc.c b/src/supervision/s6-svc.c
index 047d44d..308075d 100644
--- a/src/supervision/s6-svc.c
+++ b/src/supervision/s6-svc.c
@@ -10,7 +10,7 @@
 #include <s6/config.h>
 #include <s6/s6-supervise.h>
 
-#define USAGE "s6-svc [ -D | -U ] [ -T timeout ] [ -abqhkti12pcoduxOX ] servicedir"
+#define USAGE "s6-svc [ -wu | -wU | -wd | -wD ] [ -T timeout ] [ -abqhkti12pcoduxOX ] servicedir"
 #define dieusage() strerr_dieusage(100, USAGE)
 
 #define DATASIZE 63
@@ -26,12 +26,10 @@ int main (int argc, char const *const *argv, char const *const *envp)
     subgetopt_t l = SUBGETOPT_ZERO ;
     for (;;)
     {
-      register int opt = subgetopt_r(argc, argv, "DUabqhkti12pcoduxOXT:", &l) ;
+      register int opt = subgetopt_r(argc, argv, "abqhkti12pcoduxOXT:w:", &l) ;
       if (opt == -1) break ;
       switch (opt)
       {
-        case 'D' : updown[1] = 'd' ; break ;
-        case 'U' : updown[1] = 'U' ; break ;
         case 'a' :
         case 'b' :
         case 'q' :
@@ -55,6 +53,12 @@ int main (int argc, char const *const *argv, char const *const *envp)
           break ;
         }
         case 'T' : if (!uint0_scan(l.arg, &timeout)) dieusage() ; break ;
+        case 'w' :
+        {
+          if (byte_chr("dDuU", 4, l.arg[0]) >= 4) dieusage() ;
+          updown[1] = l.arg[0] ;
+          break ;
+        }
         default : dieusage() ;
       }
     }
@@ -63,6 +67,7 @@ int main (int argc, char const *const *argv, char const *const *envp)
   if (!argc) dieusage() ;
   if (argc > 1) strerr_warn1x("ignoring extra arguments") ;
 
+  if (datalen <= 1) return 0 ;
   if (updown[1] == 'U')
   {
     unsigned int arglen = str_len(argv[0]) ;
@@ -72,8 +77,8 @@ int main (int argc, char const *const *argv, char const *const *envp)
     if (access(fn, F_OK) < 0)
     {
       if (errno != ENOENT) strerr_diefu2sys(111, "access ", fn) ;
-      updown[1] = 0 ;
-      strerr_warnw2x(fn, " not present - ignoring -U option") ;
+      updown[1] = 'u' ;
+      strerr_warnw2x(fn, " not present - converting -wU to -wu") ;
     }
   }
 
@@ -100,15 +105,9 @@ int main (int argc, char const *const *argv, char const *const *envp)
     pathexec_run(newargv[0], newargv, envp) ;
     strerr_dieexec(111, newargv[0]) ;
   }
-  else if (datalen > 1)
+  else
   {
-    unsigned int arglen = str_len(argv[0]) ;
-    char tmp[arglen + 9 + sizeof(S6_SUPERVISE_CTLDIR)] ;
-    register int r ;
-    byte_copy(tmp, arglen, argv[0]) ;
-    tmp[arglen] = '/' ;
-    byte_copy(tmp + arglen + 1, 8 + sizeof(S6_SUPERVISE_CTLDIR), S6_SUPERVISE_CTLDIR "/control") ;
-    r = s6_svc_write(tmp, data + 1, datalen - 1) ;
+    register int r = s6_svc_writectl(argv[0], S6_SUPERVISE_CTLDIR, data + 1, datalen - 1) ;
     if (r < 0) strerr_diefu2sys(111, "control ", argv[0]) ;
     else if (!r) strerr_diefu3x(100, "control ", argv[0], ": supervisor not listening") ;
   }
diff --git a/src/supervision/s6-svlisten.c b/src/supervision/s6-svlisten.c
index 709c409..1241d72 100644
--- a/src/supervision/s6-svlisten.c
+++ b/src/supervision/s6-svlisten.c
@@ -1,64 +1,40 @@
 /* ISC license. */
 
 #include <sys/types.h>
-#include <unistd.h>
-#include <errno.h>
 #include <skalibs/sgetopt.h>
-#include <skalibs/bytestr.h>
 #include <skalibs/uint16.h>
 #include <skalibs/uint.h>
 #include <skalibs/bitarray.h>
 #include <skalibs/tai.h>
 #include <skalibs/strerr2.h>
-#include <skalibs/iopause.h>
 #include <skalibs/djbunix.h>
-#include <skalibs/sig.h>
-#include <skalibs/selfpipe.h>
 #include <execline/execline.h>
-#include <s6/ftrigr.h>
-#include <s6/s6-supervise.h>
+#include "s6-svlisten.h"
 
-#define USAGE "s6-svlisten [ -U | -u | -d ] [ -A | -a | -o ] [ -t timeout ] servicedir... \"\" prog..."
+#define USAGE "s6-svlisten [ -U | -u | -d | -D ] [ -a | -o ] [ -t timeout ] servicedir... \"\" prog..."
 #define dieusage() strerr_dieusage(100, USAGE)
 
-static inline int check (unsigned char const *ba, unsigned int n, int wantup, int or)
-{
-  return (bitarray_first(ba, n, or == wantup) < n) == or ;
-}
-
-static void handle_signals (void)
-{
-  for (;;) switch (selfpipe_read())
-  {
-    case -1 : strerr_diefu1sys(111, "selfpipe_read") ;
-    case 0 : return ;
-    case SIGCHLD : wait_reap() ; break ;
-    default : strerr_dief1x(101, "unexpected data in selfpipe") ;
-  }
-}
-
 int main (int argc, char const **argv, char const *const *envp)
 {
-  ftrigr_t a = FTRIGR_ZERO ;
   tain_t deadline, tto ;
   int spfd ;
   int argc1 ;
   int or = 0 ;
-  int wantup = 1 ;
-  char re[4] = "u|d" ;
+  int wantup = 1, wantready = 0 ;
   PROG = "s6-svlisten" ;
   {
     subgetopt_t l = SUBGETOPT_ZERO ;
     unsigned int t = 0 ;
     for (;;)
     {
-      register int opt = subgetopt_r(argc, argv, "uUdAaot:", &l) ;
+      register int opt = subgetopt_r(argc, argv, "uUdDaot:", &l) ;
       if (opt == -1) break ;
       switch (opt)
       {
-        case 'U' : wantup = 1 ; re[0] = 'U' ; break ;
-        case 'u' : wantup = 1 ; re[0] = 'u' ; break ;
-        case 'd' : wantup = 0 ; break ;
+        case 'u' : wantup = 1 ; wantready = 0 ; break ;
+        case 'U' : wantup = 1 ; wantready = 1 ; break ;
+        case 'd' : wantup = 0 ; wantready = 0 ; break ;
+        case 'D' : wantup = 0 ; wantready = 1 ; break ;
         case 'a' : or = 0 ; break ;
         case 'o' : or = 1 ; break ;
         case 't' : if (!uint0_scan(l.arg, &t)) dieusage() ; break ;
@@ -74,79 +50,19 @@ int main (int argc, char const **argv, char const *const *envp)
   if (!argc1 || argc == argc1 + 1) dieusage() ;
   if (argc1 >= argc) strerr_dief1x(100, "unterminated servicedir block") ;
 
-  spfd = selfpipe_init() ;
-  if (spfd < 0) strerr_diefu1sys(111, "selfpipe_init") ;
-  if (selfpipe_trap(SIGCHLD) < 0) strerr_diefu1sys(111, "selfpipe_trap") ;
-  if (sig_ignore(SIGPIPE) < 0) strerr_diefu1sys(111, "sig_ignore") ;
-
   tain_now_g() ;
   tain_add_g(&deadline, &tto) ;
-
-  if (!ftrigr_startf_g(&a, &deadline)) strerr_diefu1sys(111, "ftrigr_startf") ;
+  spfd = s6_svlisten_selfpipe_init() ;
 
   {
-    iopause_fd x[2] = { { .fd = spfd, .events = IOPAUSE_READ }, { .fd = ftrigr_fd(&a), .events = IOPAUSE_READ } } ;
+    s6_svlisten_t foo = S6_SVLISTEN_ZERO ;
     pid_t pid ;
-    unsigned int i = 0 ;
-    uint16 list[argc1] ;
-    unsigned char states[bitarray_div8(argc1)] ;
-    for (; i < (unsigned int)argc1 ; i++)
-    {
-      unsigned int len = str_len(argv[i]) ;
-      char s[len + 1 + sizeof(S6_SUPERVISE_EVENTDIR)] ;
-      byte_copy(s, len, argv[i]) ;
-      s[len] = '/' ;
-      byte_copy(s + len + 1, sizeof(S6_SUPERVISE_EVENTDIR), S6_SUPERVISE_EVENTDIR) ;
-      list[i] = ftrigr_subscribe_g(&a, s, re, FTRIGR_REPEAT, &deadline) ;
-      if (!list[i]) strerr_diefu2sys(111, "subscribe to events for ", argv[i]) ;
-    }
-
-    for (i = 0 ; i < (unsigned int)argc1 ; i++)
-    {
-      s6_svstatus_t st = S6_SVSTATUS_ZERO ;
-      int isup ;
-      if (!s6_svstatus_read(argv[i], &st)) strerr_diefu1sys(111, "s6_svstatus_read") ;
-      isup = !!st.pid ;
-      if (re[0] == 'U' && isup)
-      {
-        unsigned int len = str_len(argv[i]) ;
-        char s[len + 1 + sizeof(S6_SUPERVISE_READY_FILENAME)] ;
-        byte_copy(s, len, argv[i]) ;
-        s[len] = '/' ;
-        byte_copy(s + len + 1, sizeof(S6_SUPERVISE_READY_FILENAME), S6_SUPERVISE_READY_FILENAME) ;
-        if (access(s, F_OK) < 0)
-        {
-          if (errno == ENOENT) isup = 0 ;
-          else strerr_warnwu2sys("check ", s) ;
-        }
-      }
-      bitarray_poke(states, i, isup) ;
-    }
-
+    uint16 ids[argc1] ;
+    unsigned char upstate[bitarray_div8(argc1)] ;
+    unsigned char readystate[bitarray_div8(argc1)] ;
+    s6_svlisten_init(argc1, argv, &foo, ids, upstate, readystate, &deadline) ;
     pid = child_spawn0(argv[argc1 + 1], argv + argc1 + 1, envp) ;
     if (!pid) strerr_diefu2sys(111, "spawn ", argv[argc1 + 1]) ;
-
-    for (;;)
-    {
-      register int r ;
-      if (check(states, argc1, wantup, or)) break ;
-      r = iopause_g(x, 2, &deadline) ;
-      if (r < 0) strerr_diefu1sys(111, "iopause") ;
-      else if (!r) strerr_dief1x(1, "timed out") ;
-
-      if (x[0].revents & IOPAUSE_READ) handle_signals() ;
-      if (x[1].revents & IOPAUSE_READ)
-      {
-        if (ftrigr_update(&a) < 0) strerr_diefu1sys(111, "ftrigr_update") ;
-        for (i = 0 ; i < (unsigned int)argc1 ; i++)
-        {
-          char what ;
-          register int r = ftrigr_check(&a, list[i], &what) ;
-          if (r < 0) strerr_diefu1sys(111, "ftrigr_check") ;
-          if (r) bitarray_poke(states, i, what == re[0]) ;
-        }
-      } 
-    }
+    return s6_svlisten_loop(&foo, wantup, wantready, or, &deadline, spfd, &s6_svlisten_signal_handler) ;
   }
-  return 0 ;
 }
diff --git a/src/supervision/s6-svlisten.h b/src/supervision/s6-svlisten.h
new file mode 100644
index 0000000..a5d36dd
--- /dev/null
+++ b/src/supervision/s6-svlisten.h
@@ -0,0 +1,29 @@
+/* ISC license. */
+
+#ifndef S6_SVLISTEN_H
+#define S6_SVLISTEN_H
+
+#include <skalibs/uint16.h>
+#include <skalibs/tai.h>
+#include <s6/ftrigr.h>
+
+typedef void action_func_t (void) ;
+typedef action_func_t *action_func_t_ref ;
+
+typedef struct s6_svlisten_s s6_svlisten_t, *s6_svlisten_t_ref ;
+struct s6_svlisten_s
+{
+  ftrigr_t a ;
+  unsigned int n ;
+  uint16 *ids ;
+  unsigned char *upstate ;
+  unsigned char *readystate ;
+} ;
+#define S6_SVLISTEN_ZERO { .a = FTRIGR_ZERO, .n = 0, .ids = 0, .upstate = 0, .readystate = 0 }
+
+extern void s6_svlisten_signal_handler (void) ;
+extern int s6_svlisten_selfpipe_init (void) ;
+extern void s6_svlisten_init (int, char const *const *, s6_svlisten_t *, uint16 *, unsigned char *, unsigned char *, tain_t const *) ;
+extern int s6_svlisten_loop (s6_svlisten_t *, int, int, int, tain_t const *, int, action_func_t_ref) ;
+
+#endif
diff --git a/src/supervision/s6-svlisten1.c b/src/supervision/s6-svlisten1.c
index a5cecf0..32fef1f 100644
--- a/src/supervision/s6-svlisten1.c
+++ b/src/supervision/s6-svlisten1.c
@@ -1,56 +1,40 @@
 /* ISC license. */
 
 #include <sys/types.h>
-#include <unistd.h>
-#include <errno.h>
-#include <signal.h>
 #include <skalibs/sgetopt.h>
-#include <skalibs/bytestr.h>
 #include <skalibs/uint16.h>
 #include <skalibs/uint.h>
 #include <skalibs/tai.h>
 #include <skalibs/strerr2.h>
 #include <skalibs/djbunix.h>
-#include <skalibs/iopause.h>
-#include <skalibs/sig.h>
-#include <skalibs/selfpipe.h>
-#include <s6/ftrigr.h>
-#include <s6/s6-supervise.h>
+#include "s6-svlisten.h"
 
-#define USAGE "s6-svlisten1 [ -U | -u | -d ] [ -t timeout ] servicedir prog..."
+#define USAGE "s6-svlisten1 [ -U | -u | -d | -D ] [ -t timeout ] servicedir prog..."
 #define dieusage() strerr_dieusage(100, USAGE)
 
-static void handle_signals (void)
-{
-  for (;;) switch (selfpipe_read())
-  {
-    case -1 : strerr_diefu1sys(111, "selfpipe_read") ;
-    case 0 : return ;
-    case SIGCHLD : wait_reap() ; break ;
-    default : strerr_dief1x(101, "unexpected data in selfpipe") ;
-  }
-}
-
 int main (int argc, char const *const *argv, char const *const *envp)
 {
-  ftrigr_t a = FTRIGR_ZERO ;
+  s6_svlisten_t foo = S6_SVLISTEN_ZERO ;
   tain_t deadline, tto ;
+  pid_t pid ;
   int spfd ;
-  int wantup = 1 ;
-  char re[4] = "u|d" ;
+  int wantup = 1, wantready = 0 ;
+  uint16 id ;
+  unsigned char upstate, readystate ;
   PROG = "s6-svlisten1" ;
   {
     subgetopt_t l = SUBGETOPT_ZERO ;
     unsigned int t = 0 ;
     for (;;)
     {
-      register int opt = subgetopt_r(argc, argv, "uUdt:", &l) ;
+      register int opt = subgetopt_r(argc, argv, "uUdDt:", &l) ;
       if (opt == -1) break ;
       switch (opt)
       {
-        case 'U' : wantup = 1 ; re[0] = 'U' ; break ;
-        case 'u' : wantup = 1 ; re[0] = 'u' ; break ;
-        case 'd' : wantup = 0 ; break ;
+        case 'u' : wantup = 1 ; wantready = 0 ; break ;
+        case 'U' : wantup = 1 ; wantready = 1 ; break ;
+        case 'd' : wantup = 0 ; wantready = 0 ; break ;
+        case 'D' : wantup = 0 ; wantready = 1 ; break ;
         case 't' : if (!uint0_scan(l.arg, &t)) dieusage() ; break ;
         default : dieusage() ;
       }
@@ -59,63 +43,11 @@ int main (int argc, char const *const *argv, char const *const *envp)
     if (t) tain_from_millisecs(&tto, t) ; else tto = tain_infinite_relative ;
   }
   if (!argc) dieusage() ;
-
-  spfd = selfpipe_init() ;
-  if (spfd < 0) strerr_diefu1sys(111, "selfpipe_init") ;
-  if (selfpipe_trap(SIGCHLD) < 0) strerr_diefu1sys(111, "selfpipe_trap") ;
-  if (sig_ignore(SIGPIPE) < 0) strerr_diefu1sys(111, "sig_ignore") ;
-
   tain_now_g() ;
   tain_add_g(&deadline, &tto) ;
-
-  if (!ftrigr_startf_g(&a, &deadline)) strerr_diefu1sys(111, "ftrigr_startf") ;
-
-  {
-    iopause_fd x[2] = { { .fd = spfd, .events = IOPAUSE_READ }, { .fd = ftrigr_fd(&a), .events = IOPAUSE_READ } } ;
-    unsigned int arglen = str_len(argv[0]) ;
-    pid_t pid ;
-    int isup ;
-    s6_svstatus_t st = S6_SVSTATUS_ZERO ;
-    uint16 id ;
-    char s[arglen + 1 + sizeof(S6_SUPERVISE_EVENTDIR)] ;
-    byte_copy(s, arglen, argv[0]) ;
-    s[arglen] = '/' ;
-    byte_copy(s + arglen + 1, sizeof(S6_SUPERVISE_EVENTDIR), S6_SUPERVISE_EVENTDIR) ;
-    id = ftrigr_subscribe_g(&a, s, re, FTRIGR_REPEAT, &deadline) ;
-    if (!id) strerr_diefu2sys(111, "subscribe to events for ", argv[0]) ;
-    if (!s6_svstatus_read(argv[0], &st)) strerr_diefu1sys(111, "s6_svstatus_read") ;
-    isup = !!st.pid ;
-    if (re[0] == 'U' && isup)
-    {
-      byte_copy(s + arglen + 1, sizeof(S6_SUPERVISE_READY_FILENAME), S6_SUPERVISE_READY_FILENAME) ;
-      if (access(s, F_OK) < 0)
-      {
-        if (errno == ENOENT) isup = 0 ;
-        else strerr_warnwu2sys("check ", s) ;
-      }
-    }
-
-    pid = child_spawn0(argv[1], argv + 1, envp) ;
-    if (!pid) strerr_diefu2sys(111, "spawn ", argv[2]) ;
-
-    for (;;)
-    {
-      register int r ;
-      if (isup == wantup) break ;
-      r = iopause_g(x, 2, &deadline) ;
-      if (r < 0) strerr_diefu1sys(111, "iopause") ;
-      else if (!r) strerr_dief1x(1, "timed out") ;
-
-      if (x[0].revents & IOPAUSE_READ) handle_signals() ;
-      if (x[1].revents & IOPAUSE_READ)
-      {
-        char what ;
-        if (ftrigr_update(&a) < 0) strerr_diefu1sys(111, "ftrigr_update") ;
-        r = ftrigr_check(&a, id, &what) ;
-        if (r < 0) strerr_diefu1sys(111, "ftrigr_check") ;
-        if (r) isup = what == re[0] ;
-      }
-    }
-  }
-  return 0 ;
+  spfd = s6_svlisten_selfpipe_init() ;
+  s6_svlisten_init(1, argv, &foo, &id, &upstate, &readystate, &deadline) ;
+  pid = child_spawn0(argv[1], argv + 1, envp) ;
+  if (!pid) strerr_diefu2sys(111, "spawn ", argv[1]) ;
+  return s6_svlisten_loop(&foo, wantup, wantready, 1, &deadline, spfd, &s6_svlisten_signal_handler) ;
 }
diff --git a/src/supervision/s6-svscanctl.c b/src/supervision/s6-svscanctl.c
index 6529e9c..a991146 100644
--- a/src/supervision/s6-svscanctl.c
+++ b/src/supervision/s6-svscanctl.c
@@ -52,14 +52,8 @@ int main (int argc, char const *const *argv)
   }
   if (!argc) dieusage() ;
 
-  {
-    unsigned int arglen = str_len(*argv) ;
-    char tmp[arglen + 20] ;
-    byte_copy(tmp, arglen, *argv) ;
-    byte_copy(tmp + arglen, 20, "/.s6-svscan/control") ;
-    r = s6_svc_write(tmp, data, datalen) ;
-  }
-  if (r < 0) strerr_diefu2sys(111, "control ", *argv) ;
-  else if (!r) strerr_diefu3x(100, "control ", *argv, ": supervisor not listening") ;
+  r = s6_svc_writectl(argv[0], S6_SVSCAN_CTLDIR, data, datalen) ;
+  if (r < 0) strerr_diefu2sys(111, "control ", argv[0]) ;
+  else if (!r) strerr_diefu3x(100, "control ", argv[0], ": supervisor not listening") ;
   return 0 ;
 }
diff --git a/src/supervision/s6-svstat.c b/src/supervision/s6-svstat.c
index de8fe0d..bfe87a5 100644
--- a/src/supervision/s6-svstat.c
+++ b/src/supervision/s6-svstat.c
@@ -1,8 +1,8 @@
 /* ISC license. */
 
 #include <sys/types.h>
-#include <sys/stat.h>
 #include <sys/wait.h>
+#include <unistd.h>
 #include <errno.h>
 #include <skalibs/uint64.h>
 #include <skalibs/uint.h>
@@ -23,7 +23,6 @@ int main (int argc, char const *const *argv)
   s6_svstatus_t status ;
   int flagnum = 0 ;
   int isup, normallyup ;
-  tain_t readytime = TAIN_ZERO ;
   char fmt[UINT_FMT] ;
   PROG = "s6-svstat" ;
   {
@@ -49,26 +48,14 @@ int main (int argc, char const *const *argv)
   if (tain_future(&status.stamp)) tain_copynow(&status.stamp) ;
 
   {
-    char pack[TAIN_PACK] ;
-    struct stat st ;
     unsigned int dirlen = str_len(*argv) ;
-    char fn[dirlen + sizeof(S6_SUPERVISE_READY_FILENAME) + 1] ;
+    char fn[dirlen + 6] ;
     byte_copy(fn, dirlen, *argv) ;
     byte_copy(fn + dirlen, 6, "/down") ;
-    if (stat(fn, &st) == -1)
-      if (errno != ENOENT) strerr_diefu2sys(111, "stat ", fn) ;
+    if (access(fn, F_OK) < 0)
+      if (errno != ENOENT) strerr_diefu2sys(111, "access ", fn) ;
       else normallyup = 1 ;
     else normallyup = 0 ;
-    byte_copy(fn + dirlen, sizeof(S6_SUPERVISE_READY_FILENAME) + 1, "/" S6_SUPERVISE_READY_FILENAME) ;
-    if (openreadnclose(fn, pack, TAIN_PACK) < TAIN_PACK)
-    {
-      if (errno != ENOENT) strerr_warnwu2sys("read ", fn) ;
-    }
-    else
-    {
-      tain_unpack(pack, &readytime) ;
-      if (tain_future(&readytime)) tain_copynow(&readytime) ;
-    }
   }
 
   isup = status.pid && !status.flagfinishing ;
@@ -110,16 +97,16 @@ int main (int argc, char const *const *argv)
     buffer_putnoflush(buffer_1small, ", normally up", 13) ;
   if (isup && status.flagpaused)
     buffer_putnoflush(buffer_1small, ", paused", 8) ;
-  if (!isup && (status.flagwant == 'u'))
+  if (!isup && status.flagwant)
     buffer_putnoflush(buffer_1small, ", want up", 10) ;
-  if (isup && (status.flagwant == 'd'))
+  if (isup && !status.flagwant)
     buffer_putnoflush(buffer_1small, ", want down", 12) ;
 
-  if (readytime.sec.x)
+  if (status.flagready)
   {
-    tain_sub(&readytime, &STAMP, &readytime) ;
+    tain_sub(&status.readystamp, &STAMP, &status.readystamp) ;
     buffer_putnoflush(buffer_1small, ", ready ", 8) ;
-    buffer_putnoflush(buffer_1small, fmt, uint64_fmt(fmt, readytime.sec.x)) ;
+    buffer_putnoflush(buffer_1small, fmt, uint64_fmt(fmt, status.readystamp.sec.x)) ;
     buffer_putnoflush(buffer_1small, " seconds", 8) ;
   }
   if (buffer_putflush(buffer_1small, "\n", 1) < 0)
diff --git a/src/supervision/s6-svwait.c b/src/supervision/s6-svwait.c
index fa8d227..1793347 100644
--- a/src/supervision/s6-svwait.c
+++ b/src/supervision/s6-svwait.c
@@ -1,46 +1,35 @@
 /* ISC license. */
 
-#include <unistd.h>
-#include <errno.h>
 #include <skalibs/sgetopt.h>
-#include <skalibs/bytestr.h>
 #include <skalibs/uint16.h>
 #include <skalibs/uint.h>
 #include <skalibs/bitarray.h>
 #include <skalibs/tai.h>
 #include <skalibs/strerr2.h>
-#include <skalibs/iopause.h>
-#include <s6/ftrigr.h>
-#include <s6/s6-supervise.h>
+#include "s6-svlisten.h"
 
-#define USAGE "s6-svwait [ -U | -u | -d ] [ -a | -o ] [ -t timeout ] servicedir..."
+#define USAGE "s6-svwait [ -U | -u | -d | -D ] [ -a | -o ] [ -t timeout ] servicedir..."
 #define dieusage() strerr_dieusage(100, USAGE)
 
-static inline int check (unsigned char const *ba, unsigned int n, int wantup, int or)
-{
-  return (bitarray_first(ba, n, or == wantup) < n) == or ;
-}
-
 int main (int argc, char const *const *argv)
 {
   tain_t deadline, tto ;
-  ftrigr_t a = FTRIGR_ZERO ;
   int or = 0 ;
-  int wantup = 1 ;
-  char re[4] = "u|d" ;
+  int wantup = 1, wantready = 0 ;
   PROG = "s6-svwait" ;
   {
     subgetopt_t l = SUBGETOPT_ZERO ;
     unsigned int t = 0 ;
     for (;;)
     {
-      register int opt = subgetopt_r(argc, argv, "uUdaot:", &l) ;
+      register int opt = subgetopt_r(argc, argv, "UudDaot:", &l) ;
       if (opt == -1) break ;
       switch (opt)
       {
-        case 'U' : wantup = 1 ; re[0] = 'U' ; break ;
-        case 'u' : wantup = 1 ; re[0] = 'u' ; break ;
-        case 'd' : wantup = 0 ; break ;
+        case 'U' : wantup = 1 ; wantready = 1 ; break ;
+        case 'u' : wantup = 1 ; wantready = 0 ; break ;
+        case 'd' : wantup = 0 ; wantready = 0 ; break ;
+        case 'D' : wantup = 0 ; wantready = 1 ; break ;
         case 'a' : or = 0 ; break ;
         case 'o' : or = 1 ; break ;
         case 't' : if (!uint0_scan(l.arg, &t)) dieusage() ; break ;
@@ -55,65 +44,12 @@ int main (int argc, char const *const *argv)
   tain_now_g() ;
   tain_add_g(&deadline, &tto) ;
 
-  if (!ftrigr_startf_g(&a, &deadline)) strerr_diefu1sys(111, "ftrigr_startf") ;
-
   {
-    iopause_fd x = { -1, IOPAUSE_READ, 0 } ;
-    unsigned int i = 0 ;
-    uint16 list[argc] ;
-    unsigned char states[bitarray_div8(argc)] ;
-    x.fd = ftrigr_fd(&a) ;
-    for (; i < (unsigned int)argc ; i++)
-    {
-      unsigned int len = str_len(argv[i]) ;
-      char s[len + 1 + sizeof(S6_SUPERVISE_EVENTDIR)] ;
-      byte_copy(s, len, argv[i]) ;
-      s[len] = '/' ;
-      byte_copy(s + len + 1, sizeof(S6_SUPERVISE_EVENTDIR), S6_SUPERVISE_EVENTDIR) ;
-      list[i] = ftrigr_subscribe_g(&a, s, re, FTRIGR_REPEAT, &deadline) ;
-      if (!list[i]) strerr_diefu2sys(111, "subscribe to events for ", argv[i]) ;
-    }
-
-    for (i = 0 ; i < (unsigned int)argc ; i++)
-    {
-      s6_svstatus_t st = S6_SVSTATUS_ZERO ;
-      int isup ;
-      if (!s6_svstatus_read(argv[i], &st)) strerr_diefu1sys(111, "s6_svstatus_read") ;
-      isup = !!st.pid ;
-      if (re[0] == 'U' && isup)
-      {
-        unsigned int len = str_len(argv[i]) ;
-        char s[len + 1 + sizeof(S6_SUPERVISE_READY_FILENAME)] ;
-        byte_copy(s, len, argv[i]) ;
-        s[len] = '/' ;
-        byte_copy(s + len + 1, sizeof(S6_SUPERVISE_READY_FILENAME), S6_SUPERVISE_READY_FILENAME) ;
-        if (access(s, F_OK) < 0)
-        {
-          if (errno == ENOENT) isup = 0 ;
-          else strerr_warnwu2sys("check ", s) ;
-        }
-      }
-      bitarray_poke(states, i, isup) ;
-    }
-
-    for (;;)
-    {
-      if (check(states, argc, wantup, or)) break ;
-      {
-        register int r = iopause_g(&x, 1, &deadline) ;
-        if (r < 0) strerr_diefu1sys(111, "iopause") ;
-        else if (!r) strerr_dief1x(1, "timed out") ;
-      }
-
-      if (ftrigr_update(&a) < 0) strerr_diefu1sys(111, "ftrigr_update") ;
-      for (i = 0 ; i < (unsigned int)argc ; i++)
-      {
-        char what ;
-        register int r = ftrigr_check(&a, list[i], &what) ;
-        if (r < 0) strerr_diefu1sys(111, "ftrigr_check") ;
-        if (r) bitarray_poke(states, i, what == re[0]) ;
-      } 
-    }
+    s6_svlisten_t foo = S6_SVLISTEN_ZERO ;
+    uint16 ids[argc] ;
+    unsigned char upstate[bitarray_div8(argc)] ;
+    unsigned char readystate[bitarray_div8(argc)] ;
+    s6_svlisten_init(argc, argv, &foo, ids, upstate, readystate, &deadline) ;
+    return s6_svlisten_loop(&foo, wantup, wantready, or, &deadline, -1, 0) ;
   }
-  return 0 ;
 }
diff --git a/src/supervision/s6_svlisten_loop.c b/src/supervision/s6_svlisten_loop.c
new file mode 100644
index 0000000..00e911f
--- /dev/null
+++ b/src/supervision/s6_svlisten_loop.c
@@ -0,0 +1,78 @@
+/* ISC license. */
+
+#include <unistd.h>
+#include <errno.h>
+#include <skalibs/bytestr.h>
+#include <skalibs/uint16.h>
+#include <skalibs/bitarray.h>
+#include <skalibs/tai.h>
+#include <skalibs/strerr2.h>
+#include <skalibs/iopause.h>
+#include <skalibs/djbunix.h>
+#include <s6/ftrigr.h>
+#include <s6/s6-supervise.h>
+#include "s6-svlisten.h"
+
+void s6_svlisten_init (int argc, char const *const *argv, s6_svlisten_t *foo, uint16 *ids, unsigned char *upstate, unsigned char *readystate, tain_t const *deadline)
+{
+  register unsigned int i = 0 ;
+  foo->n = (unsigned int)argc ;
+  foo->ids = ids ;
+  foo->upstate = upstate ;
+  foo->readystate = readystate ;
+  if (!ftrigr_startf_g(&foo->a, deadline)) strerr_diefu1sys(111, "ftrigr_startf") ;
+  for (; i < foo->n ; i++)
+  {
+    s6_svstatus_t status = S6_SVSTATUS_ZERO ;
+    unsigned int len = str_len(argv[i]) ;
+    char s[len + 1 + sizeof(S6_SUPERVISE_EVENTDIR)] ;
+    byte_copy(s, len, argv[i]) ;
+    s[len] = '/' ;
+    byte_copy(s + len + 1, sizeof(S6_SUPERVISE_EVENTDIR), S6_SUPERVISE_EVENTDIR) ;
+    foo->ids[i] = ftrigr_subscribe_g(&foo->a, s, "D|u|U|d", FTRIGR_REPEAT, deadline) ;
+    if (!foo->ids[i]) strerr_diefu2sys(111, "subscribe to events for ", argv[i]) ;
+    if (!s6_svstatus_read(argv[i], &status)) strerr_diefu1sys(111, "s6_svstatus_read") ;
+    bitarray_poke(foo->upstate, i, status.pid && !status.flagfinishing) ;
+    bitarray_poke(foo->readystate, i, status.flagready) ;
+  }
+}
+
+static inline int got (s6_svlisten_t const *foo, int wantup, int wantready, int or)
+{
+  register unsigned int m = bitarray_div8(foo->n) ;
+  unsigned char t[m] ;
+  byte_copy(t, m, foo->upstate) ;
+  if (!wantup) bitarray_not(t, 0, foo->n) ;
+  if (wantready) bitarray_and(t, t, foo->readystate, foo->n) ;
+  return (bitarray_first(t, foo->n, or) < foo->n) == or ;
+}
+
+int s6_svlisten_loop (s6_svlisten_t *foo, int wantup, int wantready, int or, tain_t const *deadline, int spfd, action_func_t_ref handler)
+{
+  iopause_fd x[2] = { { .fd = ftrigr_fd(&foo->a), .events = IOPAUSE_READ }, { .fd = spfd, .events = IOPAUSE_READ, .revents = 0 } } ;
+  while (!got(foo, wantup, wantready, or))
+  {
+    register int r = iopause_g(x, 1 + (spfd >= 0), deadline) ;
+    if (r < 0) strerr_diefu1sys(111, "iopause") ;
+    else if (!r) strerr_dief1x(1, "timed out") ;
+    if (x[1].revents & IOPAUSE_READ) (*handler)() ;
+    if (x[0].revents & IOPAUSE_READ)
+    {
+      register unsigned int i = 0 ;
+      if (ftrigr_update(&foo->a) < 0) strerr_diefu1sys(111, "ftrigr_update") ;
+      for (; i < foo->n ; i++)
+      {
+        char what ;
+        register int r = ftrigr_check(&foo->a, foo->ids[i], &what) ;
+        if (r < 0) strerr_diefu1sys(111, "ftrigr_check") ;
+        if (r)
+        {
+          register unsigned int d = byte_chr("dDuU", 4, what) ;
+          bitarray_poke(foo->upstate, i, d & 2) ;
+          bitarray_poke(foo->readystate, i, d & 1) ;
+        }
+      }
+    }
+  }
+  return 0 ;
+}
diff --git a/src/supervision/s6_svlisten_signal_handler.c b/src/supervision/s6_svlisten_signal_handler.c
new file mode 100644
index 0000000..0738f43
--- /dev/null
+++ b/src/supervision/s6_svlisten_signal_handler.c
@@ -0,0 +1,29 @@
+/* ISC license. */
+
+#include <signal.h>
+#include <skalibs/strerr2.h>
+#include <skalibs/sig.h>
+#include <skalibs/djbunix.h>
+#include <skalibs/selfpipe.h>
+#include "s6-svlisten.h"
+
+int s6_svlisten_selfpipe_init (void)
+{
+  register int spfd = selfpipe_init() ;
+  if (spfd < 0) strerr_diefu1sys(111, "selfpipe_init") ;
+  if (selfpipe_trap(SIGCHLD) < 0) strerr_diefu1sys(111, "selfpipe_trap") ;
+  if (sig_ignore(SIGPIPE) < 0) strerr_diefu1sys(111, "ignore SIGPIPE") ;
+  return spfd ;
+}
+
+void s6_svlisten_signal_handler (void)
+{
+  for (;;) switch (selfpipe_read())
+  {
+    case -1 : strerr_diefu1sys(111, "selfpipe_read") ;
+    case 0 : return ;
+    case SIGCHLD : wait_reap() ; break ;
+    default : strerr_dief1x(101, "unexpected data in selfpipe") ;
+  }
+}
+