Implement plain simple locking in the executable memory allocator

Memory allocations may now also happen to come from a separate thread, the QML
loader thread where we also compile the JavaScript code and (likely) use the
JIT. Commonly that will be the only place where the allocator will be used. The
main thread uses the allocator only when an exception is thrown (to look up
platform unwind info) or when the garbage collector runs and decides to delete
objects that also hold the last reference to executable memory.

Change-Id: I8bb710184164cd8d32168449f48d09f7ee828e6e
Reviewed-by: Lars Knoll <lars.knoll@digia.com>

2 files changed, 13 insertions, 0 deletions

diff --git a/src/qml/jsruntime/qv4executableallocator.cpp b/src/qml/jsruntime/qv4executableallocator.cpp
index a754663556..2e80f3a611 100644
--- a/src/qml/jsruntime/qv4executableallocator.cpp
+++ b/src/qml/jsruntime/qv4executableallocator.cpp
@@ -135,6 +135,11 @@ bool ExecutableAllocator::ChunkOfPages::contains(Allocation *alloc) const
     return false;
 }
 
+ExecutableAllocator::ExecutableAllocator()
+    : mutex(QMutex::NonRecursive)
+{
+}
+
 ExecutableAllocator::~ExecutableAllocator()
 {
     qDeleteAll(chunks);
@@ -142,6 +147,7 @@ ExecutableAllocator::~ExecutableAllocator()
 
 ExecutableAllocator::Allocation *ExecutableAllocator::allocate(size_t size)
 {
+    QMutexLocker locker(&mutex);
     Allocation *allocation = 0;
 
     // Code is best aligned to 16-byte boundaries.
@@ -182,6 +188,8 @@ ExecutableAllocator::Allocation *ExecutableAllocator::allocate(size_t size)
 
 void ExecutableAllocator::free(Allocation *allocation)
 {
+    QMutexLocker locker(&mutex);
+
     assert(allocation);
 
     allocation->free = true;
@@ -210,6 +218,8 @@ void ExecutableAllocator::free(Allocation *allocation)
 
 ExecutableAllocator::ChunkOfPages *ExecutableAllocator::chunkForAllocation(Allocation *allocation) const
 {
+    QMutexLocker locker(&mutex);
+
     QMap<quintptr, ChunkOfPages*>::ConstIterator it = chunks.lowerBound(allocation->addr);
     if (it != chunks.begin())
         --it;
diff --git a/src/qml/jsruntime/qv4executableallocator_p.h b/src/qml/jsruntime/qv4executableallocator_p.h
index 2a304baf9c..feba5d7e3d 100644
--- a/src/qml/jsruntime/qv4executableallocator_p.h
+++ b/src/qml/jsruntime/qv4executableallocator_p.h
@@ -48,6 +48,7 @@
 #include <QHash>
 #include <QVector>
 #include <QByteArray>
+#include <QMutex>
 
 namespace WTF {
 class PageAllocation;
@@ -63,6 +64,7 @@ public:
     struct ChunkOfPages;
     struct Allocation;
 
+    ExecutableAllocator();
     ~ExecutableAllocator();
 
     Allocation *allocate(size_t size);
@@ -125,6 +127,7 @@ public:
 private:
     QMultiMap<size_t, Allocation*> freeAllocations;
     QMap<quintptr, ChunkOfPages*> chunks;
+    mutable QMutex mutex;
 };
 
 }