Add some doc, improve s6-background-watch

2 files changed, 25 insertions, 16 deletions

diff --git a/src/supervision/s6-background-watch.c b/src/supervision/s6-background-watch.c
index cfb1fb7..847e844 100644
--- a/src/supervision/s6-background-watch.c
+++ b/src/supervision/s6-background-watch.c
@@ -124,7 +124,8 @@ static inline int handle_signals (pid_t pid, int issr, int *code)
 }
 
 
-/* BSD part. kevent is a unique snowflake in the shape of a dildo */
+/* BSD part. kevent is a unique dildo-shaped snowflake, so we need to run it
+   in its own thread for it to play nicely with our regular iopause loop. */
 
 #ifdef SKALIBS_HASKEVENT
 
@@ -162,7 +163,6 @@ static void keventstart (pid_t pid, int *fd, pthread_t *th)
   EV_SET(&ke, pid, EVFILT_PROC, EV_ADD | EV_ONESHOT, NOTE_EXIT, 0, 0) ;
   if (kevent(t.kq, &ke, 1, 0, 0, 0) == -1) strerr_diefu1sys(111, "register kevent") ;
   if (pipe(p) == -1) strerr_diefu2sys(111, "pipe") ;
-  if (coe(p[0]) 
   t.fdw = p[1] ;
   t.pid = pid ;
   e = pthread_attr_init(&attr) ;
@@ -201,7 +201,7 @@ static gol_arg const rgola[GOLA_N] =
 
 int main (int argc, char const *const *argv)
 {
-  iopause_fd x[2] = { { .events = IOPAUSE_READ }, { .events = IOPAUSE_READ, .revents = 0 } } ;
+  iopause_fd x[2] = { { .events = IOPAUSE_READ }, { .fd = -2, .events = IOPAUSE_READ, .revents = 0 } } ;
   tain tto = TAIN_INFINITE_RELATIVE ;
   tain deadline ;
   unsigned int notif = 0 ;
@@ -238,7 +238,6 @@ int main (int argc, char const *const *argv)
 #ifdef SKALIBS_HASPRSETCHILDSUBREAPER
   if (prctl(PR_SET_CHILD_SUBREAPER, 1) == -1)
     strerr_diefu1sys(111, "prctl to become a subreaper") ;
-  x[1].fd = -2 ;
 #endif
 
   pid = cspawn(argv[1], argv + 1, (char const *const *)environ, CSPAWN_FLAGS_SELFPIPE_FINISH, 0, 0) ;
@@ -259,8 +258,10 @@ int main (int argc, char const *const *argv)
   }
 
   pid = get_pid_from_pidfile(argv[0], argv[1]) ;
+  if (kill(pid, 0) == -1) strerr_diefu1sys(111, "check daemon with a null signal") ;
+
 #ifdef SKALIBS_HASKEVENT
-  pthread_t th ;
+  pthread_t th = PTHREAD_NULL ;
   keventstart(pid, &x[1].fd, &th) ;
 #endif
   if (notif)
diff --git a/src/supervision/s6-supervise.c b/src/supervision/s6-supervise.c
index 6feb7c4..8567bb1 100644
--- a/src/supervision/s6-supervise.c
+++ b/src/supervision/s6-supervise.c
@@ -297,16 +297,18 @@ static void trystart (void)
     [0] = { .type = CSPAWN_FA_CLOSE },
     [1] = { .type = CSPAWN_FA_MOVE },
   } ;
-  char lkfmt[UINT_FMT] ;
-  char const *cargv[8] = { S6_BINPREFIX "s6-setlock", "-d", lkfmt, "--", SLCK, "./run", servicename, 0 } ;
-  size_t orig = 5 ;
+  char const *cargv[8] ;
   int notifyp[2] = { -1, -1 } ;
   unsigned int lk = 0, notif = 0 ;
   uint16_t cspawnflags = CSPAWN_FLAGS_SELFPIPE_FINISH | CSPAWN_FLAGS_SETSID ;
+  uint8_t m = 0 ;
+  char lkfmt[UINT_FMT] ;
+
+  if (check_file("flag-newpidns")) cspawnflags |= CSPAWN_FLAGS_NEWPIDNS ;
 
   if (read_uint("lock-fd", &lk))
   {
-    if (lk > maxfd) strerr_warnw2x("invalid ", "lock-fd") ;
+    if (!lk || lk > maxfd) strerr_warnw2x("invalid ", "lock-fd") ;
     else
     {
       struct stat st ;
@@ -342,14 +344,18 @@ static void trystart (void)
         strerr_warnw1x("another instance of the service is already running, child will block") ;
       fd_close(lfd) ;
       lkfmt[uint_fmt(lkfmt, lk)] = 0 ;
-      orig = 0 ;
+      cargv[m++] = S6_BINPREFIX "s6-setlock" ;
+      cargv[m++] = "-d" ;
+      cargv[m++] = lkfmt ;
+      cargv[m++] = "--" ;
+      cargv[m++] = SLCK ;
     }
   }
 
   if (read_uint("notification-fd", &notif))
   {
-    if (notif > maxfd) strerr_warnw2x("invalid ", "notification-fd") ;
-    if (!orig && notif == lk)
+    if (!notif || notif > maxfd) strerr_warnw2x("invalid ", "notification-fd") ;
+    if (notif == lk)
     {
       settimeout_infinite() ;
       strerr_warnwu1x("start service: notification-fd and lock-fd are the same") ;
@@ -366,12 +372,14 @@ static void trystart (void)
     fa[1].x.fd2[1] = notifyp[1] ;
   }
 
-  if (check_file("flag-newpidns")) cspawnflags |= CSPAWN_FLAGS_NEWPIDNS ;
-  status.pid = cspawn(cargv[orig], cargv + orig, (char const *const *)environ, cspawnflags, fa, notifyp[1] >= 0 ? 2 : 0) ;
+  cargv[m++] = "./run" ;
+  cargv[m++] = servicename ;
+  cargv[m++] = 0 ;
+  status.pid = cspawn(cargv[0], cargv, (char const *const *)environ, cspawnflags, fa, notifyp[1] >= 0 ? 2 : 0) ;
   if (!status.pid)
   {
     settimeout(60) ;
-    strerr_warnwu3sys("spawn ", cargv[orig], " (waiting 60 seconds)") ;
+    strerr_warnwu3sys("spawn ", cargv[0], " (waiting 60 seconds)") ;
     goto errn ;
   }
 
@@ -382,7 +390,7 @@ static void trystart (void)
   }
   status.pgid = getpgid(status.pid) ;
   if (status.pgid == -1)
-    strerr_warnwu1sys("getpgid() (process group control commands will have no effect)") ;
+    strerr_warnwu1sys("getpgid (process group control commands will have no effect)") ;
   settimeout_infinite() ;
   nextstart = tain_zero ;
   state = UP ;