From: Ben Langmuir <blangmuir@apple.com>
Date: Thu, 19 Feb 2015 18:22:35 +0000 (+0000)
Subject: Assume the original file is created before release in LockFileManager
X-Git-Url: http://demsky.eecs.uci.edu/git/?a=commitdiff_plain;h=7b5766d2f62ccf40de9dd385216d7ba39dcebc0d;p=oota-llvm.git

Assume the original file is created before release in LockFileManager

This is true in clang, and let's us remove the problematic code that
waits around for the original file and then times out if it doesn't get
created in short order.  This caused any 'dead' lock file or legitimate
time out to cause a cascade of timeouts in any processes waiting on the
same lock (even if they only just showed up).

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@229881 91177308-0d34-0410-b5e6-96231b3b80d8
---

diff --git a/lib/Support/LockFileManager.cpp b/lib/Support/LockFileManager.cpp
index 9ec52ac5409..ec3158c3bc1 100644
--- a/lib/Support/LockFileManager.cpp
+++ b/lib/Support/LockFileManager.cpp
@@ -187,8 +187,7 @@ LockFileManager::WaitForUnlockResult LockFileManager::waitForUnlock() {
   Interval.tv_nsec = 1000000;
 #endif
   // Don't wait more than one minute for the file to appear.
-  unsigned MaxSeconds = 60;
-  bool LockFileGone = false;
+  const unsigned MaxSeconds = 60;
   do {
     // Sleep for the designated interval, to allow the owning process time to
     // finish up and remove the lock file.
@@ -199,47 +198,18 @@ LockFileManager::WaitForUnlockResult LockFileManager::waitForUnlock() {
 #else
     nanosleep(&Interval, nullptr);
 #endif
-    bool LockFileJustDisappeared = false;
 
-    // If the lock file is still expected to be there, check whether it still
-    // is.
-    if (!LockFileGone) {
-      if (sys::fs::access(LockFileName.c_str(), sys::fs::AccessMode::Exist) ==
-          errc::no_such_file_or_directory) {
-        LockFileGone = true;
-        LockFileJustDisappeared = true;
-      }
+    if (sys::fs::access(LockFileName.c_str(), sys::fs::AccessMode::Exist) ==
+        errc::no_such_file_or_directory) {
+      // If the original file wasn't created, somone thought the lock was dead.
+      if (!sys::fs::exists(FileName.str()))
+        return Res_OwnerDied;
+      return Res_Success;
     }
 
-    // If the lock file is no longer there, check if the original file is
-    // available now.
-    if (LockFileGone) {
-      if (sys::fs::exists(FileName.str())) {
-        return Res_Success;
-      }
-
-      // The lock file is gone, so now we're waiting for the original file to
-      // show up. If this just happened, reset our waiting intervals and keep
-      // waiting.
-      if (LockFileJustDisappeared) {
-        MaxSeconds = 5;
-
-#if LLVM_ON_WIN32
-        Interval = 1;
-#else
-        Interval.tv_sec = 0;
-        Interval.tv_nsec = 1000000;
-#endif
-        continue;
-      }
-    }
-
-    // If we're looking for the lock file to disappear, but the process
-    // owning the lock died without cleaning up, just bail out.
-    if (!LockFileGone &&
-        !processStillExecuting((*Owner).first, (*Owner).second)) {
+    // If the process owning the lock died without cleaning up, just bail out.
+    if (!processStillExecuting((*Owner).first, (*Owner).second))
       return Res_OwnerDied;
-    }
 
     // Exponentially increase the time we wait for the lock to be removed.
 #if LLVM_ON_WIN32