Added a mutex to the call frame info to guard

generation of the FDE index.

<rdar://problem/11813705>

llvm-svn: 160099

lldb/include/lldb/Symbol/DWARFCallFrameInfo.h

@@ -18,6 +18,7 @@
 #include "lldb/Core/AddressRange.h"
 #include "lldb/Core/VMRange.h"
 #include "lldb/Core/dwarf.h"
+#include "lldb/Host/Mutex.h"
 #include "lldb/Symbol/UnwindPlan.h"
 #include "lldb/Symbol/ObjectFile.h"
 
@@ -128,6 +129,7 @@ private:
 
     std::vector<FDEEntry>       m_fde_index;
     bool                        m_fde_index_initialized;  // only scan the section for FDEs once
+    Mutex                       m_fde_index_mutex;        // and isolate the thread that does it
 
     bool                        m_is_eh_frame;
 

lldb/source/Symbol/DWARFCallFrameInfo.cpp

@@ -293,9 +293,14 @@ DWARFCallFrameInfo::GetFDEIndex ()
 {
     if (m_section_sp.get() == NULL || m_section_sp->IsEncrypted())
         return;
+    
     if (m_fde_index_initialized)
         return;
-
+    
+    Mutex::Locker locker(m_fde_index_mutex);
+    
+    if (m_fde_index_initialized) // if two threads hit the locker
+        return;
 
     dw_offset_t offset = 0;
     if (m_cfi_data_initialized == false)