SL-20743 Use LLMutex in LLImageBase for internal data thread-safety

4 files changed, 256 insertions, 13 deletions

diff --git a/indra/llcommon/llapr.cpp b/indra/llcommon/llapr.cpp
index 575c524219..834b0e7a3a 100644
--- a/indra/llcommon/llapr.cpp
+++ b/indra/llcommon/llapr.cpp
@@ -571,7 +571,7 @@ S32 LLAPRFile::readEx(const std::string& filename, void *buf, S32 offset, S32 nb
 }
 
 //static
-S32 LLAPRFile::writeEx(const std::string& filename, void *buf, S32 offset, S32 nbytes, LLVolatileAPRPool* pool)
+S32 LLAPRFile::writeEx(const std::string& filename, const void *buf, S32 offset, S32 nbytes, LLVolatileAPRPool* pool)
 {
     LL_PROFILE_ZONE_SCOPED;
 	apr_int32_t flags = APR_CREATE|APR_WRITE|APR_BINARY;
diff --git a/indra/llcommon/llapr.h b/indra/llcommon/llapr.h
index 565d7cfb63..f5717ea75e 100644
--- a/indra/llcommon/llapr.h
+++ b/indra/llcommon/llapr.h
@@ -193,7 +193,7 @@ public:
 
 	// Returns bytes read/written, 0 if read/write fails:
 	static S32 readEx(const std::string& filename, void *buf, S32 offset, S32 nbytes, LLVolatileAPRPool* pool = NULL);	
-	static S32 writeEx(const std::string& filename, void *buf, S32 offset, S32 nbytes, LLVolatileAPRPool* pool = NULL); // offset<0 means append
+	static S32 writeEx(const std::string& filename, const void *buf, S32 offset, S32 nbytes, LLVolatileAPRPool* pool = NULL); // offset<0 means append
 //*******************************************************************************************************************************
 };
 
diff --git a/indra/llcommon/llmutex.cpp b/indra/llcommon/llmutex.cpp
index 0273dd5970..f56c2d08a6 100644
--- a/indra/llcommon/llmutex.cpp
+++ b/indra/llcommon/llmutex.cpp
@@ -29,19 +29,20 @@
 #include "llthread.h"
 #include "lltimer.h"
 
-//============================================================================
 
+//---------------------------------------------------------------------
+//
+// LLMutex
+//
 LLMutex::LLMutex() :
  mCount(0)
 {
 }
 
-
 LLMutex::~LLMutex()
 {
 }
 
-
 void LLMutex::lock()
 {
     LL_PROFILE_ZONE_SCOPED_CATEGORY_THREAD
@@ -112,7 +113,7 @@ LLThread::id_t LLMutex::lockingThread() const
 bool LLMutex::trylock()
 {
     LL_PROFILE_ZONE_SCOPED_CATEGORY_THREAD
-	if(isSelfLocked())
+	if (isSelfLocked())
 	{ //redundant lock
 		mCount++;
 		return true;
@@ -135,19 +136,185 @@ bool LLMutex::trylock()
 	return true;
 }
 
-//============================================================================
 
+//---------------------------------------------------------------------
+//
+// LLSharedMutex
+//
+LLSharedMutex::LLSharedMutex()
+: mLockingThreads(2) // Reserve 2 slots in the map hash table
+, mIsShared(false)
+{
+}
+
+bool LLSharedMutex::isLocked() const
+{
+    LL_PROFILE_ZONE_SCOPED_CATEGORY_THREAD
+    std::lock_guard<std::mutex> lock(mLockMutex);
+
+    return !mLockingThreads.empty();
+}
+
+bool LLSharedMutex::isThreadLocked() const
+{
+    LL_PROFILE_ZONE_SCOPED_CATEGORY_THREAD
+    LLThread::id_t current_thread = LLThread::currentID();
+    std::lock_guard<std::mutex> lock(mLockMutex);
+
+    const_iterator it = mLockingThreads.find(current_thread);
+    return it != mLockingThreads.end();
+}
+
+void LLSharedMutex::lockShared()
+{
+    LL_PROFILE_ZONE_SCOPED_CATEGORY_THREAD
+    LLThread::id_t current_thread = LLThread::currentID();
+
+    mLockMutex.lock();
+    iterator it = mLockingThreads.find(current_thread);
+    if (it != mLockingThreads.end())
+    {
+        it->second++;
+    }
+    else
+    {
+        // Acquire the mutex immediately if the mutex is not locked exclusively
+        // or enter a locking state if the mutex is already locked exclusively
+        mLockMutex.unlock();
+        mSharedMutex.lock_shared();
+        mLockMutex.lock();
+        // Continue after acquiring the mutex
+        mLockingThreads.emplace(std::make_pair(current_thread, 1));
+        mIsShared = true;
+    }
+    mLockMutex.unlock();
+}
+
+void LLSharedMutex::lockExclusive()
+{
+    LL_PROFILE_ZONE_SCOPED_CATEGORY_THREAD
+    LLThread::id_t current_thread = LLThread::currentID();
+
+    mLockMutex.lock();
+    if (mLockingThreads.size() == 1 && mLockingThreads.begin()->first == current_thread)
+    {
+        mLockingThreads.begin()->second++;
+    }
+    else
+    {
+        // Acquire the mutex immediately if mLockingThreads is empty
+        // or enter a locking state if mLockingThreads is not empty
+        mLockMutex.unlock();
+        mSharedMutex.lock();
+        mLockMutex.lock();
+        // Continue after acquiring the mutex (and possible quitting the locking state)
+        mLockingThreads.emplace(std::make_pair(current_thread, 1));
+        mIsShared = false;
+    }
+    mLockMutex.unlock();
+}
+
+bool LLSharedMutex::trylockShared()
+{
+    LL_PROFILE_ZONE_SCOPED_CATEGORY_THREAD
+    LLThread::id_t current_thread = LLThread::currentID();
+    std::lock_guard<std::mutex> lock(mLockMutex);
+
+    iterator it = mLockingThreads.find(current_thread);
+    if (it != mLockingThreads.end())
+    {
+        it->second++;
+    }
+    else
+    {
+        if (!mSharedMutex.try_lock_shared())
+            return false;
+
+        mLockingThreads.emplace(std::make_pair(current_thread, 1));
+        mIsShared = true;
+    }
+
+    return true;
+}
+
+bool LLSharedMutex::trylockExclusive()
+{
+    LL_PROFILE_ZONE_SCOPED_CATEGORY_THREAD
+    LLThread::id_t current_thread = LLThread::currentID();
+    std::lock_guard<std::mutex> lock(mLockMutex);
+
+    if (mLockingThreads.size() == 1 && mLockingThreads.begin()->first == current_thread)
+    {
+        mLockingThreads.begin()->second++;
+    }
+    else
+    {
+        if (!mSharedMutex.try_lock())
+            return false;
+
+        mLockingThreads.emplace(std::make_pair(current_thread, 1));
+        mIsShared = false;
+    }
+
+    return true;
+}
+
+void LLSharedMutex::unlockShared()
+{
+    LL_PROFILE_ZONE_SCOPED_CATEGORY_THREAD
+    LLThread::id_t current_thread = LLThread::currentID();
+    std::lock_guard<std::mutex> lock(mLockMutex);
+
+    iterator it = mLockingThreads.find(current_thread);
+    if (it != mLockingThreads.end())
+    {
+        if (it->second > 1)
+        {
+            it->second--;
+        }
+        else
+        {
+            mLockingThreads.erase(it);
+            mSharedMutex.unlock_shared();
+        }
+    }
+}
+
+void LLSharedMutex::unlockExclusive()
+{
+    LL_PROFILE_ZONE_SCOPED_CATEGORY_THREAD
+    LLThread::id_t current_thread = LLThread::currentID();
+    std::lock_guard<std::mutex> lock(mLockMutex);
+
+    iterator it = mLockingThreads.find(current_thread);
+    if (it != mLockingThreads.end())
+    {
+        if (it->second > 1)
+        {
+            it->second--;
+        }
+        else
+        {
+            mLockingThreads.erase(it);
+            mSharedMutex.unlock();
+        }
+    }
+}
+
+
+//---------------------------------------------------------------------
+//
+// LLCondition
+//
 LLCondition::LLCondition() :
 	LLMutex()
 {
 }
 
-
 LLCondition::~LLCondition()
 {
 }
 
-
 void LLCondition::wait()
 {
     LL_PROFILE_ZONE_SCOPED_CATEGORY_THREAD
@@ -168,7 +335,10 @@ void LLCondition::broadcast()
 }
 
 
-
+//---------------------------------------------------------------------
+//
+// LLMutexTrylock
+//
 LLMutexTrylock::LLMutexTrylock(LLMutex* mutex)
     : mMutex(mutex),
     mLocked(false)
diff --git a/indra/llcommon/llmutex.h b/indra/llcommon/llmutex.h
index 0d70da6178..077f810d61 100644
--- a/indra/llcommon/llmutex.h
+++ b/indra/llcommon/llmutex.h
@@ -32,6 +32,8 @@
 #include <boost/noncopyable.hpp>
 
 #include "mutex.h"
+#include <shared_mutex>
+#include <unordered_map>
 #include <condition_variable>
 
 //============================================================================
@@ -66,6 +68,45 @@ protected:
 #endif
 };
 
+//============================================================================
+
+class LL_COMMON_API LLSharedMutex
+{
+public:
+    LLSharedMutex();
+
+    bool isLocked() const;
+    bool isThreadLocked() const;
+    bool isShared() const { return mIsShared; }
+
+    void lockShared();
+    void lockExclusive();
+    template<bool SHARED> void lock();
+    template<> void lock<true>() { lockShared(); }
+    template<> void lock<false>() { lockExclusive(); }
+
+    bool trylockShared();
+    bool trylockExclusive();
+    template<bool SHARED> bool trylock();
+    template<> bool trylock<true>() { return trylockShared(); }
+    template<> bool trylock<false>() { return trylockExclusive(); }
+
+    void unlockShared();
+    void unlockExclusive();
+    template<bool SHARED> void unlock();
+    template<> void unlock<true>() { unlockShared(); }
+    template<> void unlock<false>() { unlockExclusive(); }
+
+private:
+    std::shared_mutex mSharedMutex;
+    mutable std::mutex mLockMutex;
+    std::unordered_map<LLThread::id_t, U32> mLockingThreads;
+    bool mIsShared;
+
+    using iterator = std::unordered_map<LLThread::id_t, U32>::iterator;
+    using const_iterator = std::unordered_map<LLThread::id_t, U32>::const_iterator;
+};
+
 // Actually a condition/mutex pair (since each condition needs to be associated with a mutex).
 class LL_COMMON_API LLCondition : public LLMutex
 {
@@ -81,27 +122,57 @@ protected:
 	std::condition_variable mCond;
 };
 
+//============================================================================
+
 class LLMutexLock
 {
 public:
 	LLMutexLock(LLMutex* mutex)
 	{
 		mMutex = mutex;
-		
-		if(mMutex)
+
+		if (mMutex)
 			mMutex->lock();
 	}
+
 	~LLMutexLock()
 	{
-		if(mMutex)
+		if (mMutex)
 			mMutex->unlock();
 	}
+
 private:
 	LLMutex* mMutex;
 };
 
 //============================================================================
 
+template<bool SHARED>
+class LLSharedMutexLockTemplate
+{
+public:
+    LLSharedMutexLockTemplate(LLSharedMutex* mutex)
+    : mSharedMutex(mutex)
+    {
+        if (mSharedMutex)
+            mSharedMutex->lock<SHARED>();
+    }
+
+    ~LLSharedMutexLockTemplate()
+    {
+        if (mSharedMutex)
+            mSharedMutex->unlock<SHARED>();
+    }
+
+private:
+    LLSharedMutex* mSharedMutex;
+};
+
+using LLSharedMutexLock = LLSharedMutexLockTemplate<true>;
+using LLExclusiveMutexLock = LLSharedMutexLockTemplate<false>;
+
+//============================================================================
+
 // Scoped locking class similar in function to LLMutexLock but uses
 // the trylock() method to conditionally acquire lock without
 // blocking.  Caller resolves the resulting condition by calling
@@ -127,6 +198,8 @@ private:
 	bool		mLocked;
 };
 
+//============================================================================
+
 /**
 * @class LLScopedLock
 * @brief Small class to help lock and unlock mutexes.