From 5a1191300ccd289813a4b71d504ebdb495e7132c Mon Sep 17 00:00:00 2001
From: Paul Beckingham <paul@beckingham.net>
Date: Thu, 2 Jul 2009 21:16:24 -0400
Subject: [PATCH] Enhancement - file locking

- While waiting for a lock, display a message to that effect,
  otherwise it looks like task is hung (thanks to John Florian).
---
 src/TDB.cpp | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/src/TDB.cpp b/src/TDB.cpp
index e4fd78dbb..06977aa1c 100644
--- a/src/TDB.cpp
+++ b/src/TDB.cpp
@@ -655,8 +655,12 @@ FILE* TDB::openAndLock (const std::string& file)
   // Lock if desired.  Try three times before failing.
   int retry = 0;
   if (mLock)
-    while (flock (fileno (in), LOCK_EX) && ++retry <= 3)
-      delay (0.1);
+    while (flock (fileno (in), LOCK_NB | LOCK_EX) && ++retry <= 3)
+    {
+      std::cout << "Waiting for file lock..." << std::endl;
+      while (flock (fileno (in), LOCK_EX) && ++retry <= 3)
+        delay (0.2);
+    }
 
   if (retry > 3)
     throw std::string ("Could not lock '") + file + "'.";