From 9f8391e292f6e4ffd72437fcfb86afb42af33654 Mon Sep 17 00:00:00 2001
From: Boris Kolpackov <boris@codesynthesis.com>
Date: Thu, 7 Feb 2019 12:57:58 +0200
Subject: Fix race in machine check

---
 bbot/agent/agent.cxx | 22 +++++++++++++++-------
 1 file changed, 15 insertions(+), 7 deletions(-)

diff --git a/bbot/agent/agent.cxx b/bbot/agent/agent.cxx
index be3b706..83db6d7 100644
--- a/bbot/agent/agent.cxx
+++ b/bbot/agent/agent.cxx
@@ -263,7 +263,7 @@ bootstrap_machine (const dir_path& md,
             break;
 
           if (!check_machine ())
-            return r;
+            return nullopt;
         }
 
         // This can mean two things: machine mis-configuration or what we
@@ -301,6 +301,14 @@ bootstrap_machine (const dir_path& md,
           if (tftpd.serve (to, 2))
             continue;
 
+          if (!check_machine ())
+          {
+            // The exit/upload is racy so we re-check.
+            //
+            if (!(file_not_empty (mf) || file_not_empty (mfo)))
+              return nullopt;
+          }
+
           bool old (false);
           if (file_not_empty (mf) || (old = file_not_empty (mfo)))
           {
@@ -313,9 +321,6 @@ bootstrap_machine (const dir_path& md,
             if (!tftpd.serve (to, 5))
               break;
           }
-
-          if (!check_machine ())
-            return nullopt;
         }
 
         if (to == 0)
@@ -981,14 +986,17 @@ try
           if (tftpd.serve (to, 2))
             continue;
 
+          if (!check_machine ())
+          {
+            if (!file_not_empty (rf))
+              return r;
+          }
+
           if (file_not_empty (rf))
           {
             if (!tftpd.serve (to, 5))
               break;
           }
-
-          if (!check_machine ())
-            return r;
         }
 
         if (to == 0)
-- 
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