Improving MCJIT/RuntimeDyld thread safety

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@193094 91177308-0d34-0410-b5e6-96231b3b80d8

2 files changed, 19 insertions, 0 deletions

diff --git a/lib/ExecutionEngine/RuntimeDyld/RuntimeDyld.cpp b/lib/ExecutionEngine/RuntimeDyld/RuntimeDyld.cpp
index 07de4ba8cd..f40bed1b3f 100644
--- a/lib/ExecutionEngine/RuntimeDyld/RuntimeDyld.cpp
+++ b/lib/ExecutionEngine/RuntimeDyld/RuntimeDyld.cpp
@@ -19,6 +19,7 @@
 #include "RuntimeDyldMachO.h"
 #include "llvm/Support/FileSystem.h"
 #include "llvm/Support/MathExtras.h"
+#include "llvm/Support/MutexGuard.h"
 #include "llvm/Object/ELF.h"
 
 using namespace llvm;
@@ -37,6 +38,8 @@ void RuntimeDyldImpl::deregisterEHFrames() {
 
 // Resolve the relocations for all symbols we currently know about.
 void RuntimeDyldImpl::resolveRelocations() {
+  MutexGuard locked(lock);
+
   // First, resolve relocations associated with external symbols.
   resolveExternalSymbols();
 
@@ -57,6 +60,7 @@ void RuntimeDyldImpl::resolveRelocations() {
 
 void RuntimeDyldImpl::mapSectionAddress(const void *LocalAddress,
                                         uint64_t TargetAddress) {
+  MutexGuard locked(lock);
   for (unsigned i = 0, e = Sections.size(); i != e; ++i) {
     if (Sections[i].Address == LocalAddress) {
       reassignSectionAddress(i, TargetAddress);
@@ -73,6 +77,8 @@ ObjectImage *RuntimeDyldImpl::createObjectImage(ObjectBuffer *InputBuffer) {
 }
 
 ObjectImage *RuntimeDyldImpl::loadObject(ObjectBuffer *InputBuffer) {
+  MutexGuard locked(lock);
+
   OwningPtr<ObjectImage> obj(createObjectImage(InputBuffer));
   if (!obj)
     report_fatal_error("Unable to create object image from memory buffer!");
diff --git a/lib/ExecutionEngine/RuntimeDyld/RuntimeDyldImpl.h b/lib/ExecutionEngine/RuntimeDyld/RuntimeDyldImpl.h
index 465d05bf2c..3014b30773 100644
--- a/lib/ExecutionEngine/RuntimeDyld/RuntimeDyldImpl.h
+++ b/lib/ExecutionEngine/RuntimeDyld/RuntimeDyldImpl.h
@@ -25,6 +25,7 @@
 #include "llvm/Support/ErrorHandling.h"
 #include "llvm/Support/Format.h"
 #include "llvm/Support/Host.h"
+#include "llvm/Support/Mutex.h"
 #include "llvm/Support/SwapByteOrder.h"
 #include "llvm/Support/raw_ostream.h"
 #include "llvm/Support/system_error.h"
@@ -186,6 +187,18 @@ protected:
   Triple::ArchType Arch;
   bool IsTargetLittleEndian;
 
+  // This mutex prevents simultaneously loading objects from two different
+  // threads.  This keeps us from having to protect individual data structures
+  // and guarantees that section allocation requests to the memory manager
+  // won't be interleaved between modules.  It is also used in mapSectionAddress
+  // and resolveRelocations to protect write access to internal data structures.
+  //
+  // loadObject may be called on the same thread during the handling of of
+  // processRelocations, and that's OK.  The handling of the relocation lists
+  // is written in such a way as to work correctly if new elements are added to
+  // the end of the list while the list is being processed.
+  sys::Mutex lock;
+
   virtual unsigned getMaxStubSize() = 0;
   virtual unsigned getStubAlignment() = 0;