close fd early, no need to carry file descriptors around

app/vmmd.ml

@@ -34,7 +34,7 @@ let create process cont =
     state := state'' ;
     s := { !s with vm_created = succ !s.vm_created } ;
     Lwt.async (fun () ->
-        Vmm_lwt.wait_and_clear vm.Unikernel.pid vm.Unikernel.stdout >>= fun r ->
+        Vmm_lwt.wait_and_clear vm.Unikernel.pid >>= fun r ->
         let state', out' = Vmm_vmmd.handle_shutdown !state name vm r in
         s := { !s with vm_destroyed = succ !s.vm_destroyed } ;
         state := state' ;

src/vmm_core.ml

@@ -180,7 +180,6 @@ module Unikernel = struct
     cmd : Bos.Cmd.t ;
     pid : int ;
     taps : string list ;
-    stdout : Unix.file_descr (* ringbuffer thingy *)
   }
 
   let pp ppf vm =

src/vmm_core.mli

@@ -75,7 +75,6 @@ module Unikernel : sig
     cmd : Bos.Cmd.t;
     pid : int;
     taps : string list;
-    stdout : Unix.file_descr;
   }
 
   val pp : t Fmt.t

src/vmm_lwt.ml

@@ -29,10 +29,9 @@ let rec waitpid pid =
                      (Printexc.to_string e) pid) ;
         Lwt.return (Error ()))
 
-let wait_and_clear pid stdout =
+let wait_and_clear pid =
   Logs.debug (fun m -> m "waitpid() for pid %d" pid) ;
   waitpid pid >|= fun r ->
-  Vmm_unix.close_no_err stdout ;
   match r with
   | Error () ->
     Logs.err (fun m -> m "waitpid() for %d returned error" pid) ;

src/vmm_lwt.mli

@@ -8,7 +8,7 @@ val ret : Unix.process_status -> Vmm_core.process_exit
 
 val waitpid : int -> (int * Lwt_unix.process_status, unit) result Lwt.t
 
-val wait_and_clear : int -> Unix.file_descr -> Vmm_core.process_exit Lwt.t
+val wait_and_clear : int -> Vmm_core.process_exit Lwt.t
 
 val read_wire : Lwt_unix.file_descr ->
   (Vmm_commands.wire, [> `Eof | `Exception | `Toomuch ]) result Lwt.t

src/vmm_unix.ml

@@ -37,10 +37,10 @@ let null = match read_fd_for_file (Fpath.v "/dev/null") with
   | Ok fd -> fd
   | Error _ -> invalid_arg "cannot read /dev/null"
 
-let rec create_process prog args stdout stderr =
+let rec create_process prog args stdout =
-  try Unix.create_process prog args null stdout stderr with
+  try Unix.create_process prog args null stdout stdout with
   | Unix.Unix_error (Unix.EINTR, _, _) ->
-      create_process prog args stdout stderr
+      create_process prog args stdout
 
 let rec close fd =
   try Unix.close fd with
@@ -175,11 +175,14 @@ let exec name vm taps block =
   Logs.debug (fun m -> m "opened file descriptor!");
   try
     Logs.debug (fun m -> m "creating process");
-    let pid = create_process prog line stdout stdout in
+    let pid = create_process prog line stdout in
     Logs.debug (fun m -> m "created process %d: %a" pid Bos.Cmd.pp cmd) ;
+    (* we gave a copy (well, two copies) of that file descriptor to the solo5
+       process and don't really need it here anymore... *)
+    close stdout ;
     (* this should get rid of the vmimage from vmmd's memory! *)
     let config = Unikernel.{ vm with image = (fst vm.Unikernel.image, Cstruct.create 0) } in
-    Ok Unikernel.{ config ; cmd ; pid ; taps ; stdout }
+    Ok Unikernel.{ config ; cmd ; pid ; taps }
   with
     Unix.Unix_error (e, _, _) ->
     close_no_err stdout;