USR2 upgrades may use Process.spawn for vfork

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.

1 files changed, 16 insertions, 17 deletions

diff --git a/lib/yahns/server.rb b/lib/yahns/server.rb
index 00e5f15..5411c48 100644
--- a/lib/yahns/server.rb
+++ b/lib/yahns/server.rb
@@ -237,24 +237,23 @@ class Yahns::Server # :nodoc:
       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