From fa3e35d2e925533ef0ce6a9d2272eaffec4f43d4 Mon Sep 17 00:00:00 2001
From: Steven Woods <steven.woods@citrix.com>
Date: Wed, 4 Jan 2023 11:20:14 +0000
Subject: [PATCH] CP-32622: Replace select with polly in xn

Signed-off-by: Steven Woods <steven.woods@citrix.com>
---
 ocaml/xenopsd/cli/dune  |  1 +
 ocaml/xenopsd/cli/xn.ml | 53 +++++++++++++++++++++++++----------------
 2 files changed, 33 insertions(+), 21 deletions(-)

diff --git a/ocaml/xenopsd/cli/dune b/ocaml/xenopsd/cli/dune
index 220d5aae2e2..1ca310dd079 100644
--- a/ocaml/xenopsd/cli/dune
+++ b/ocaml/xenopsd/cli/dune
@@ -9,6 +9,7 @@
       astring
       cmdliner
       dune-build-info
+      polly
       re
       result
       rpclib.core
diff --git a/ocaml/xenopsd/cli/xn.ml b/ocaml/xenopsd/cli/xn.ml
index 079bea26db9..86d286969b8 100644
--- a/ocaml/xenopsd/cli/xn.ml
+++ b/ocaml/xenopsd/cli/xn.ml
@@ -1176,27 +1176,38 @@ let raw_console_proxy sockaddr =
       ) else if !final then
         finished := true
       else
-        let r, _, _ = Unix.select [Unix.stdin; fd] [] [] (-1.) in
-        if List.mem Unix.stdin r then (
-          let b =
-            Unix.read Unix.stdin buf_remote !buf_remote_end
-              (block - !buf_remote_end)
-          in
-          let i = ref !buf_remote_end in
-          while
-            !i < !buf_remote_end + b
-            && Char.code (Bytes.get buf_remote !i) <> 0x1d
-          do
-            incr i
-          done ;
-          if !i < !buf_remote_end + b then final := true ;
-          buf_remote_end := !i
-        ) ;
-        if List.mem fd r then
-          let b =
-            Unix.read fd buf_local !buf_local_end (block - !buf_local_end)
-          in
-          buf_local_end := !buf_local_end + b
+        let epoll = Polly.create () in
+        List.iter
+          (fun fd -> Polly.add epoll fd Polly.Events.inp)
+          [Unix.stdin; fd] ;
+        Fun.protect
+          ~finally:(fun () -> Polly.close epoll)
+          (fun () ->
+            ignore
+            @@ Polly.wait epoll 2 (-1) (fun _ file_desc _ ->
+                   if Unix.stdin = file_desc then (
+                     let b =
+                       Unix.read Unix.stdin buf_remote !buf_remote_end
+                         (block - !buf_remote_end)
+                     in
+                     let i = ref !buf_remote_end in
+                     while
+                       !i < !buf_remote_end + b
+                       && Char.code (Bytes.get buf_remote !i) <> 0x1d
+                     do
+                       incr i
+                     done ;
+                     if !i < !buf_remote_end + b then final := true ;
+                     buf_remote_end := !i
+                   ) ;
+                   if fd = file_desc then
+                     let b =
+                       Unix.read fd buf_local !buf_local_end
+                         (block - !buf_local_end)
+                     in
+                     buf_local_end := !buf_local_end + b
+               )
+          )
     done
   in
   let delay = ref 0.1 in