From 0d93247359531388f88f22f85326e1142d801e85 Mon Sep 17 00:00:00 2001
From: Monty Brandenberg <monty@lindenlab.com>
Date: Tue, 6 Aug 2013 18:05:34 -0400
Subject: SH-4411  Thread/mutex rework between main and worker thread Have the
 ::notifyLoadedMeshes() method doing correct locking and stall avoidance at
 the same time.  This method now does lazy mutex lock acquisition (trylock())
 and if it fails on either, it gives up and comes back later.  Capture the
 maximum number of sequential failures and report this at the end of the run
 in the log.  (So far, with big mesh regions, I've only seen 1s and 2s.) 
 Locking/mutex requirements sorted in other locations as well.  LLMutex gets
 trylock() method as well as new LLMutexTrylock scoped locking class.  Clean
 up some documentation, more to do.

---
 indra/llcommon/llthread.cpp | 32 +++++++++++++++++++++++++++++++-
 1 file changed, 31 insertions(+), 1 deletion(-)

(limited to 'indra/llcommon/llthread.cpp')

diff --git a/indra/llcommon/llthread.cpp b/indra/llcommon/llthread.cpp
index 1d56a52c32..7563975959 100755
--- a/indra/llcommon/llthread.cpp
+++ b/indra/llcommon/llthread.cpp
@@ -3,7 +3,7 @@
  *
  * $LicenseInfo:firstyear=2004&license=viewerlgpl$
  * Second Life Viewer Source Code
- * Copyright (C) 2010, Linden Research, Inc.
+ * Copyright (C) 2010-2013, Linden Research, Inc.
  * 
  * This library is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Lesser General Public
@@ -372,6 +372,36 @@ void LLMutex::lock()
 #endif
 }
 
+bool LLMutex::trylock()
+{
+	if(isSelfLocked())
+	{ //redundant lock
+		mCount++;
+		return true;
+	}
+	
+	apr_status_t status(apr_thread_mutex_trylock(mAPRMutexp));
+	if (APR_STATUS_IS_EBUSY(status))
+	{
+		return false;
+	}
+	
+#if MUTEX_DEBUG
+	// Have to have the lock before we can access the debug info
+	U32 id = LLThread::currentID();
+	if (mIsLocked[id] != FALSE)
+		llerrs << "Already locked in Thread: " << id << llendl;
+	mIsLocked[id] = TRUE;
+#endif
+
+#if LL_DARWIN
+	mLockingThread = LLThread::currentID();
+#else
+	mLockingThread = sThreadID;
+#endif
+	return true;
+}
+
 void LLMutex::unlock()
 {
 	if (mCount > 0)
-- 
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