When calling TypeSystemMap::Clear, objects being destroyed in the process of

clearing the map ended up calling back into the TypeSystemMap to do lookups.  
Not a good idea, and in this case it would cause a deadlock.

You would only see this when replacing the target contents after an exec, and only if you 
had stopped before the exec, evaluated an expression, then continued
on to the point where you did the exec.  

Fixed this by making sure the TypeSystemMap::Clear tears down the TypeSystems in the map before clearing the map.
I also add an expression before exec to the TestExec.py so that we'll catch this
issue if it crops up again in the future.

<rdar://problem/24554920>

llvm-svn: 260624

5 files changed, 70 insertions, 36 deletions

diff --git a/lldb/include/lldb/Symbol/ClangASTContext.h b/lldb/include/lldb/Symbol/ClangASTContext.h
index 3eb7446f6d0..d30fb2eb223 100644
--- a/lldb/include/lldb/Symbol/ClangASTContext.h
+++ b/lldb/include/lldb/Symbol/ClangASTContext.h
@@ -61,6 +61,9 @@ public:
 
     ~ClangASTContext() override;
 
+    void
+    Finalize() override;
+
     //------------------------------------------------------------------
     // PluginInterface functions
     //------------------------------------------------------------------
@@ -127,7 +130,7 @@ public:
 
     void
     Clear();
-
+    
     const char *
     GetTargetTriple ();
 
diff --git a/lldb/include/lldb/Symbol/TypeSystem.h b/lldb/include/lldb/Symbol/TypeSystem.h
index 7df974fcd32..83372ad4aaf 100644
--- a/lldb/include/lldb/Symbol/TypeSystem.h
+++ b/lldb/include/lldb/Symbol/TypeSystem.h
@@ -92,6 +92,12 @@ public:
     static lldb::TypeSystemSP
     CreateInstance (lldb::LanguageType language, Target *target);
 
+     
+    // Free up any resources associated with this TypeSystem.  Done before removing
+    // all the TypeSystems from the TypeSystemMap.
+    virtual void
+    Finalize() {}
+
     virtual DWARFASTParser *
     GetDWARFParser ()
     {
@@ -584,6 +590,8 @@ protected:
         TypeSystemMap ();
         ~TypeSystemMap();
 
+        // Clear calls Finalize on all the TypeSystems managed by this map, and then
+        // empties the map.
         void
         Clear ();
 
diff --git a/lldb/packages/Python/lldbsuite/test/functionalities/exec/TestExec.py b/lldb/packages/Python/lldbsuite/test/functionalities/exec/TestExec.py
index e84ddd6cd28..912d51fb6b0 100644
--- a/lldb/packages/Python/lldbsuite/test/functionalities/exec/TestExec.py
+++ b/lldb/packages/Python/lldbsuite/test/functionalities/exec/TestExec.py
@@ -56,15 +56,18 @@ class ExecTestCase(TestBase):
             self.assertTrue(process.GetState() == lldb.eStateStopped,
                             STOPPED_DUE_TO_BREAKPOINT)
 
-            thread = process.GetThreadAtIndex (0)
+            threads = lldbutil.get_threads_stopped_at_breakpoint(process, breakpoint)
+            self.assertTrue(len(threads) == 1)
 
-            self.assertTrue (thread.IsValid(),
-                             "Process stopped at 'main' should have a valid thread");
+            # We had a deadlock tearing down the TypeSystemMap on exec, but only if some
+            # expression had been evaluated.  So make sure we do that here so the teardown
+            # is not trivial.
 
-            stop_reason = thread.GetStopReason()
-            
-            self.assertTrue (stop_reason == lldb.eStopReasonBreakpoint,
-                             "Thread in process stopped in 'main' should have a stop reason of eStopReasonBreakpoint");
+            thread = threads[0]
+            value = thread.frames[0].EvaluateExpression("1 + 2")
+            self.assertTrue(value.IsValid(), "Expression evaluated successfully")
+            int_value = value.GetValueAsSigned()
+            self.assertTrue(int_value == 3, "Expression got the right result.")
 
             # Run and we should stop due to exec
             process.Continue()
@@ -72,15 +75,11 @@ class ExecTestCase(TestBase):
             self.assertTrue(process.GetState() == lldb.eStateStopped,
                             "Process should be stopped at __dyld_start")
                         
-            thread = process.GetThreadAtIndex (0)
-        
-            self.assertTrue (thread.IsValid(),
-                             "Process stopped at exec should have a valid thread");
-        
-            stop_reason = thread.GetStopReason()
-        
-            self.assertTrue (stop_reason == lldb.eStopReasonExec,
-                             "Thread in process stopped on exec should have a stop reason of eStopReasonExec");
-        
+            threads = lldbutil.get_stopped_threads(process, lldb.eStopReasonExec)
+            self.assertTrue(len(threads) == 1, "We got a thread stopped for exec.")
+
              # Run and we should stop at breakpoint in main after exec
             process.Continue()        
+
+            threads = lldbutil.get_threads_stopped_at_breakpoint(process, breakpoint)
+            self.assertTrue(len(threads) == 1, "Stopped at breakpoint in exec'ed process.")
diff --git a/lldb/source/Symbol/ClangASTContext.cpp b/lldb/source/Symbol/ClangASTContext.cpp
index f953ddb21e4..1d4d265e702 100644
--- a/lldb/source/Symbol/ClangASTContext.cpp
+++ b/lldb/source/Symbol/ClangASTContext.cpp
@@ -333,22 +333,7 @@ ClangASTContext::ClangASTContext (const char *target_triple) :
 //----------------------------------------------------------------------
 ClangASTContext::~ClangASTContext()
 {
-    if (m_ast_ap.get())
-    {
-        GetASTMap().Erase(m_ast_ap.get());
-        if (!m_ast_owned)
-            m_ast_ap.release();
-    }
-
-    m_builtins_ap.reset();
-    m_selector_table_ap.reset();
-    m_identifier_table_ap.reset();
-    m_target_info_ap.reset();
-    m_target_options_rp.reset();
-    m_diagnostics_engine_ap.reset();
-    m_source_manager_ap.reset();
-    m_language_options_ap.reset();
-    m_ast_ap.reset();
+    Finalize();
 }
 
 ConstString
@@ -472,6 +457,27 @@ ClangASTContext::Terminate()
     PluginManager::UnregisterPlugin (CreateInstance);
 }
 
+void
+ClangASTContext::Finalize()
+{
+    if (m_ast_ap.get())
+    {
+        GetASTMap().Erase(m_ast_ap.get());
+        if (!m_ast_owned)
+            m_ast_ap.release();
+    }
+
+    m_builtins_ap.reset();
+    m_selector_table_ap.reset();
+    m_identifier_table_ap.reset();
+    m_target_info_ap.reset();
+    m_target_options_rp.reset();
+    m_diagnostics_engine_ap.reset();
+    m_source_manager_ap.reset();
+    m_language_options_ap.reset();
+    m_ast_ap.reset();
+    m_scratch_ast_source_ap.reset();
+}
 
 void
 ClangASTContext::Clear()
diff --git a/lldb/source/Symbol/TypeSystem.cpp b/lldb/source/Symbol/TypeSystem.cpp
index 5b8e935c71d..5354f22a10f 100644
--- a/lldb/source/Symbol/TypeSystem.cpp
+++ b/lldb/source/Symbol/TypeSystem.cpp
@@ -176,8 +176,26 @@ TypeSystemMap::~TypeSystemMap()
 void
 TypeSystemMap::Clear ()
 {
-    Mutex::Locker locker (m_mutex);
-    m_map.clear();
+    collection map;
+    {
+        Mutex::Locker locker (m_mutex);
+        map = m_map;
+    }
+    std::set<TypeSystem *> visited;
+    for (auto pair : map)
+    {
+        TypeSystem *type_system = pair.second.get();
+        if (type_system && !visited.count(type_system))
+        {
+            visited.insert(type_system);
+            type_system->Finalize();
+        }
+    }
+    map.clear();
+    {
+        Mutex::Locker locker (m_mutex);
+        m_map.clear();
+    }
 }