Add a lock to PlatformPOSIX::DoLoadImage

Summary:
Multiple threads could be calling into DoLoadImage concurrently,
only one should be allowed to create the UtilityFunction.

Reviewers: jingham

Subscribers: emaste, lldb-commits

Differential Revision: https://reviews.llvm.org/D46733

llvm-svn: 332115

2 files changed, 16 insertions, 22 deletions

diff --git a/lldb/source/Plugins/Platform/POSIX/PlatformPOSIX.cpp b/lldb/source/Plugins/Platform/POSIX/PlatformPOSIX.cpp
index f7a82651022..9b2c86a5f68 100644
--- a/lldb/source/Plugins/Platform/POSIX/PlatformPOSIX.cpp
+++ b/lldb/source/Plugins/Platform/POSIX/PlatformPOSIX.cpp
@@ -929,10 +929,9 @@ Status PlatformPOSIX::EvaluateLibdlExpression(
   return Status();
 }
 
-UtilityFunction *
-PlatformPOSIX::MakeLoadImageUtilityFunction(ExecutionContext &exe_ctx, 
-                                            Status &error)
-{
+std::unique_ptr<UtilityFunction>
+PlatformPOSIX::MakeLoadImageUtilityFunction(ExecutionContext &exe_ctx,
+                                            Status &error) {
   // Remember to prepend this with the prefix from
   // GetLibdlFunctionDeclarations. The returned values are all in
   // __lldb_dlopen_result for consistency. The wrapper returns a void * but
@@ -982,7 +981,6 @@ PlatformPOSIX::MakeLoadImageUtilityFunction(ExecutionContext &exe_ctx,
   Value value;
   ValueList arguments;
   FunctionCaller *do_dlopen_function = nullptr;
-  UtilityFunction *dlopen_utility_func = nullptr;
 
   // Fetch the clang types we will need:
   ClangASTContext *ast = process->GetTarget().GetScratchClangASTContext();
@@ -1015,9 +1013,7 @@ PlatformPOSIX::MakeLoadImageUtilityFunction(ExecutionContext &exe_ctx,
   }
   
   // We made a good utility function, so cache it in the process:
-  dlopen_utility_func = dlopen_utility_func_up.get();
-  process->SetLoadImageUtilityFunction(std::move(dlopen_utility_func_up));
-  return dlopen_utility_func;
+  return dlopen_utility_func_up;
 }
 
 uint32_t PlatformPOSIX::DoLoadImage(lldb_private::Process *process,
@@ -1038,18 +1034,16 @@ uint32_t PlatformPOSIX::DoLoadImage(lldb_private::Process *process,
   thread_sp->CalculateExecutionContext(exe_ctx);
 
   Status utility_error;
-  
-  // The UtilityFunction is held in the Process.  Platforms don't track the
-  // lifespan of the Targets that use them, we can't put this in the Platform.
-  UtilityFunction *dlopen_utility_func 
-      = process->GetLoadImageUtilityFunction(this);
+  UtilityFunction *dlopen_utility_func;
   ValueList arguments;
   FunctionCaller *do_dlopen_function = nullptr;
-  
-  if (!dlopen_utility_func) {
-    // Make the UtilityFunction:
-    dlopen_utility_func = MakeLoadImageUtilityFunction(exe_ctx, error);
-  }
+
+  // The UtilityFunction is held in the Process.  Platforms don't track the
+  // lifespan of the Targets that use them, we can't put this in the Platform.
+  dlopen_utility_func = process->GetLoadImageUtilityFunction(
+      this, [&]() -> std::unique_ptr<UtilityFunction> {
+        return MakeLoadImageUtilityFunction(exe_ctx, error);
+      });
   // If we couldn't make it, the error will be in error, so we can exit here.
   if (!dlopen_utility_func)
     return LLDB_INVALID_IMAGE_TOKEN;
diff --git a/lldb/source/Plugins/Platform/POSIX/PlatformPOSIX.h b/lldb/source/Plugins/Platform/POSIX/PlatformPOSIX.h
index 1235e21f30d..12d6c6209f0 100644
--- a/lldb/source/Plugins/Platform/POSIX/PlatformPOSIX.h
+++ b/lldb/source/Plugins/Platform/POSIX/PlatformPOSIX.h
@@ -199,10 +199,10 @@ protected:
   EvaluateLibdlExpression(lldb_private::Process *process, const char *expr_cstr,
                           llvm::StringRef expr_prefix,
                           lldb::ValueObjectSP &result_valobj_sp);
-  
-  lldb_private::UtilityFunction *                        
-  MakeLoadImageUtilityFunction(lldb_private::ExecutionContext &exe_ctx, 
-                               lldb_private::Status &error); 
+
+  std::unique_ptr<lldb_private::UtilityFunction>
+  MakeLoadImageUtilityFunction(lldb_private::ExecutionContext &exe_ctx,
+                               lldb_private::Status &error);
 
   virtual
   llvm::StringRef GetLibdlFunctionDeclarations(lldb_private::Process *process);