From 2a4e570485e8dee285843ca46f6dd6155972c437 Mon Sep 17 00:00:00 2001
From: Laurent Bercot <ska-skaware@skarnet.org>
Date: Tue, 6 Jun 2023 19:27:21 +0000
Subject:  Add notification to shutdownd

This saves 1 second between stage 3 and stage 4.

Signed-off-by: Laurent Bercot <ska@appnovation.com>
---
 doc/s6-linux-init-shutdownd.html       |  9 ++++++++-
 doc/upgrade.html                       |  2 ++
 src/init/s6-linux-init-maker.c         |  3 ++-
 src/shutdown/s6-linux-init-shutdownd.c | 17 +++++++++++++++--
 4 files changed, 27 insertions(+), 4 deletions(-)

diff --git a/doc/s6-linux-init-shutdownd.html b/doc/s6-linux-init-shutdownd.html
index b0d42f4..7b504d9 100644
--- a/doc/s6-linux-init-shutdownd.html
+++ b/doc/s6-linux-init-shutdownd.html
@@ -27,7 +27,7 @@ directly by the user.
 <h2> Interface </h2>
 
 <pre>
-     s6-linux-init-shutdownd [ -c <em>basedir</em> ] [ -g <em>gracetime</em> ] [ -C ] [ -B ]
+     s6-linux-init-shutdownd [ -d <em>notif</em> ] [ -c <em>basedir</em> ] [ -g <em>gracetime</em> ] [ -C ] [ -B ]
 </pre>
 
 <ul>
@@ -51,6 +51,13 @@ machine. </li>
 <h2> Options </h2>
 
 <ul>
+ <li> <tt>-d</tt>&nbsp;<em>notif</em>&nbsp;: when ready
+(actually listening to its named pipe),
+write a newline to file descriptor <em>notif</em> then close it.
+This allows s6-linux-init-shutdownd to use the
+<a href="//skarnet.org/software/s6/notifywhenup.html">s6 mechanism to notify
+readiness</a>. <em>notif</em> cannot be lesser than 3.
+If this option is not given, no readiness notification is sent. </li>
  <li> <tt>-c&nbsp;<em>basedir</em></tt>&nbsp;: look for the
 <em>rc.shutdown</em> script in the <em>basedir</em><tt>/scripts</tt>
 directory. Default is <tt>/etc/s6-linux-init/current</tt>. </li>
diff --git a/doc/upgrade.html b/doc/upgrade.html
index 8133a41..8c5e25a 100644
--- a/doc/upgrade.html
+++ b/doc/upgrade.html
@@ -23,6 +23,8 @@
 <ul>
  <li> <a href="//skarnet.org/software/skalibs/">skalibs</a>
 dependency bumped to 2.13.2.0. </li>
+ <li> You should run <a href="s6-linux-init-maker.html">s6-linux-init-maker</a>
+again to take advantage of a minor bugfix. </li>
 </ul>
 
 <h2> in 1.1.1.1 </h2>
diff --git a/src/init/s6-linux-init-maker.c b/src/init/s6-linux-init-maker.c
index 98b9b46..d3b921d 100644
--- a/src/init/s6-linux-init-maker.c
+++ b/src/init/s6-linux-init-maker.c
@@ -186,7 +186,7 @@ static int shutdownd_script (buffer *b, char const *data)
   size_t sabase = satmp.len ;
   char fmt[UINT_FMT] ;
   if (!put_shebang(b)
-   || buffer_puts(b, S6_LINUX_INIT_EXTBINPREFIX "s6-linux-init-shutdownd -c ") < 0
+   || buffer_puts(b, S6_LINUX_INIT_EXTBINPREFIX "s6-linux-init-shutdownd -d3 -c ") < 0
    || !string_quote(&satmp, robase, strlen(robase))) return 0 ;
   if (buffer_put(b, satmp.s + sabase, satmp.len - sabase) < 0) goto err ;
   satmp.len = sabase ;
@@ -527,6 +527,7 @@ static inline void make_image (char const *base)
 
   auto_dir(base, "run-image/" S6_LINUX_INIT_SCANDIR "/" SHUTDOWND_SERVICEDIR, 0, 0, 0755) ;
   auto_fifo(base, "run-image/" S6_LINUX_INIT_SCANDIR "/" SHUTDOWND_SERVICEDIR "/" SHUTDOWND_FIFO) ;
+  auto_file(base, "run-image/" S6_LINUX_INIT_SCANDIR "/" SHUTDOWND_SERVICEDIR "/notification-fd", "3\n", 2) ;
   auto_script(base, "run-image/" S6_LINUX_INIT_SCANDIR "/" SHUTDOWND_SERVICEDIR "/run", &shutdownd_script, 0) ;
 
   if (inns)
diff --git a/src/shutdown/s6-linux-init-shutdownd.c b/src/shutdown/s6-linux-init-shutdownd.c
index be84baf..8b2741a 100644
--- a/src/shutdown/s6-linux-init-shutdownd.c
+++ b/src/shutdown/s6-linux-init-shutdownd.c
@@ -43,7 +43,7 @@
 #define DOTSUFFIXLEN (sizeof(DOTSUFFIX) - 1)
 #define CONTAINERDIR S6_LINUX_INIT_TMPFS "/" CONTAINER_RESULTS
 
-#define USAGE "s6-linux-init-shutdownd [ -c basedir ] [ -g gracetime ] [ -C ] [ -B ]"
+#define USAGE "s6-linux-init-shutdownd [ -d notif ] [ -c basedir ] [ -g gracetime ] [ -C ] [ -B ]"
 #define dieusage() strerr_dieusage(100, USAGE)
 
 static char const *basedir = BASEDIR ;
@@ -255,6 +255,7 @@ int main (int argc, char const *const *argv)
   unsigned int grace_time = 3000 ;
   tain deadline ;
   int fdr, fdw ;
+  unsigned int notif = 0 ;
   buffer b ;
   char what = 'S' ;
   char buf[64] ;
@@ -264,10 +265,11 @@ int main (int argc, char const *const *argv)
     subgetopt l = SUBGETOPT_ZERO ;
     for (;;)
     {
-      int opt = subgetopt_r(argc, argv, "c:g:CB", &l) ;
+      int opt = subgetopt_r(argc, argv, "d:c:g:CB", &l) ;
       if (opt == -1) break ;
       switch (opt)
       {
+        case 'd' : if (!uint0_scan(l.arg, &notif)) dieusage() ; break ;
         case 'c' : basedir = l.arg ; break ;
         case 'g' : if (!uint0_scan(l.arg, &grace_time)) dieusage() ; break ;
         case 'C' : inns = 1 ; break ;
@@ -279,6 +281,11 @@ int main (int argc, char const *const *argv)
   }
   if (basedir[0] != '/')
     strerr_dief2x(100, "basedir", " must be an absolute path") ;
+  if (notif)
+  {
+    if (notif < 3) strerr_dief1x(100, "notification fd must be 3 or more") ;
+    if (fcntl(notif, F_GETFD) < 0) strerr_dief1sys(100, "invalid notification fd") ;
+  }
   if (grace_time > 300000) grace_time = 300000 ;
 
  /* if we're in stage 4, exec it immediately */
@@ -315,6 +322,12 @@ int main (int argc, char const *const *argv)
   buffer_init(&b, &buffer_read, fdr, buf, 64) ;
   tain_now_set_stopwatch_g() ;
   tain_add_g(&deadline, &tain_infinite_relative) ;
+  if (notif)
+  {
+    write(notif, "\n", 1) ;
+    close(notif) ;
+    notif = 0 ;
+  }
 
   for (;;)
   {
-- 
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