[PATCH] USR2 upgrades may use Process.spawn for vfork

[Eric Wong <yahns-public@yhbt.net>]

Remove false statements about close-on-exec being cleared in the
parent process (verified via strace) and refactor the code to
take full advantage of options for Process.spawn and Process.exec.

This avoids unnecessary CoW traffic for the common case where
before_exec is unset.
---
 lib/yahns/server.rb | 33 ++++++++++++++++-----------------
 1 file changed, 16 insertions(+), 17 deletions(-)

diff --git a/lib/yahns/server.rb b/lib/yahns/server.rb
index 861b919..43caae6 100644
--- a/lib/yahns/server.rb
+++ b/lib/yahns/server.rb
@@ -237,24 +237,23 @@ def reexec
       end
     end
 
-    # We cannot use Process.spawn here because of redirects + close-on-exec
-    # We must keep close_on_exec=true in the parent process and only set
-    # close_on_exec=false in the child.  There must be no opportunity
-    # for the user app to ever get a listen socket with close_on_exec=false
-    @reexec_pid = fork do
-      redirects = {}
-      @listeners.each do |sock|
-        sock.close_on_exec = false
-        redirects[sock.fileno] = sock
+    opt = {}
+    @listeners.each { |sock| opt[sock.fileno] = sock }
+    env = ENV.to_hash
+    env['YAHNS_FD'] = opt.keys.join(',')
+    opt[:close_others] = true
+    cmd = [ Yahns::START[0] ].concat(Yahns::START[:argv])
+    dir = @config.value(:working_directory) || Yahns::START[:cwd]
+    @logger.info "spawning #{cmd.inspect} (in #{dir})"
+    @reexec_pid = if @before_exec
+      fork do
+        Dir.chdir(dir)
+        @before_exec.call(cmd)
+        exec(env, *cmd, opt)
       end
-      ENV['YAHNS_FD'] = redirects.keys.join(',')
-      redirects[:close_others] = true
-      Dir.chdir(@config.value(:working_directory) || Yahns::START[:cwd])
-      cmd = [ Yahns::START[0] ].concat(Yahns::START[:argv])
-      @logger.info "executing #{cmd.inspect} (in #{Dir.pwd})"
-      @before_exec.call(cmd) if @before_exec
-      cmd << redirects
-      exec(*cmd)
+    else
+      opt[:chdir] = dir
+      spawn(env, *cmd, opt)
     end
   end
 
-- 
EW