[Lldb-commits] [lldb] r289169 - Calling SBDebugger::CeeateTarget being called on multiple threads was crashing LLDB.

[Greg Clayton via lldb-commits]

Author: gclayton
Date: Thu Dec  8 19:21:14 2016
New Revision: 289169

URL: http://llvm.org/viewvc/llvm-project?rev=289169&view=rev
Log:
Calling SBDebugger::CeeateTarget being called on multiple threads was crashing LLDB.

I found the race condition in:

ScriptInterpreter *CommandInterpreter::GetScriptInterpreter(bool can_create);

More than one "ScriptInterpreter *" was being returned due to the race which caused any clients with the first one to now be pointing to freed memory and we would quickly crash.

Added a test to catch this so we don't regress.

<rdar://problem/28356584> 


Added:
    lldb/trunk/packages/Python/lldbsuite/test/api/multiple-targets/
    lldb/trunk/packages/Python/lldbsuite/test/api/multiple-targets/Makefile
    lldb/trunk/packages/Python/lldbsuite/test/api/multiple-targets/TestMultipleTargets.py
    lldb/trunk/packages/Python/lldbsuite/test/api/multiple-targets/main.cpp
Modified:
    lldb/trunk/include/lldb/Interpreter/CommandInterpreter.h
    lldb/trunk/source/Interpreter/CommandInterpreter.cpp

Modified: lldb/trunk/include/lldb/Interpreter/CommandInterpreter.h
URL: http://llvm.org/viewvc/llvm-project/lldb/trunk/include/lldb/Interpreter/CommandInterpreter.h?rev=289169&r1=289168&r2=289169&view=diff
==============================================================================
--- lldb/trunk/include/lldb/Interpreter/CommandInterpreter.h (original)
+++ lldb/trunk/include/lldb/Interpreter/CommandInterpreter.h Thu Dec  8 19:21:14 2016
@@ -12,6 +12,7 @@
 
 // C Includes
 // C++ Includes
+#include <mutex>
 // Other libraries and framework includes
 // Project includes
 #include "lldb/Core/Broadcaster.h"
@@ -538,6 +539,7 @@ private:
   std::string m_repeat_command; // Stores the command that will be executed for
                                 // an empty command string.
   lldb::ScriptInterpreterSP m_script_interpreter_sp;
+  std::mutex m_script_interpreter_mutex;
   lldb::IOHandlerSP m_command_io_handler_sp;
   char m_comment_char;
   bool m_batch_command_mode;

Added: lldb/trunk/packages/Python/lldbsuite/test/api/multiple-targets/Makefile
URL: http://llvm.org/viewvc/llvm-project/lldb/trunk/packages/Python/lldbsuite/test/api/multiple-targets/Makefile?rev=289169&view=auto
==============================================================================
--- lldb/trunk/packages/Python/lldbsuite/test/api/multiple-targets/Makefile (added)
+++ lldb/trunk/packages/Python/lldbsuite/test/api/multiple-targets/Makefile Thu Dec  8 19:21:14 2016
@@ -0,0 +1,8 @@
+LEVEL = ../../make
+
+MAKE_DSYM := NO
+
+ENABLE_THREADS := YES
+CXX_SOURCES := main.cpp
+
+include $(LEVEL)/Makefile.rules

Added: lldb/trunk/packages/Python/lldbsuite/test/api/multiple-targets/TestMultipleTargets.py
URL: http://llvm.org/viewvc/llvm-project/lldb/trunk/packages/Python/lldbsuite/test/api/multiple-targets/TestMultipleTargets.py?rev=289169&view=auto
==============================================================================
--- lldb/trunk/packages/Python/lldbsuite/test/api/multiple-targets/TestMultipleTargets.py (added)
+++ lldb/trunk/packages/Python/lldbsuite/test/api/multiple-targets/TestMultipleTargets.py Thu Dec  8 19:21:14 2016
@@ -0,0 +1,39 @@
+"""Test the lldb public C++ api when creating multiple targets simultaneously."""
+
+from __future__ import print_function
+
+
+import os
+import re
+import subprocess
+
+import lldb
+from lldbsuite.test.decorators import *
+from lldbsuite.test.lldbtest import *
+from lldbsuite.test import lldbutil
+
+
+class TestMultipleSimultaneousDebuggers(TestBase):
+
+    mydir = TestBase.compute_mydir(__file__)
+
+    @skipIfNoSBHeaders
+    def test_multiple_debuggers(self):
+        env = {self.dylibPath: self.getLLDBLibraryEnvVal()}
+
+        self.driver_exe = os.path.join(os.getcwd(), "multi-target")
+        self.buildDriver('main.cpp', self.driver_exe)
+        self.addTearDownHook(lambda: os.remove(self.driver_exe))
+        self.signBinary(self.driver_exe)
+
+# check_call will raise a CalledProcessError if multi-process-driver doesn't return
+# exit code 0 to indicate success.  We can let this exception go - the test harness
+# will recognize it as a test failure.
+
+        if self.TraceOn():
+            print("Running test %s" % self.driver_exe)
+            check_call([self.driver_exe, self.driver_exe], env=env)
+        else:
+            with open(os.devnull, 'w') as fnull:
+                check_call([self.driver_exe, self.driver_exe],
+                           env=env, stdout=fnull, stderr=fnull)

Added: lldb/trunk/packages/Python/lldbsuite/test/api/multiple-targets/main.cpp
URL: http://llvm.org/viewvc/llvm-project/lldb/trunk/packages/Python/lldbsuite/test/api/multiple-targets/main.cpp?rev=289169&view=auto
==============================================================================
--- lldb/trunk/packages/Python/lldbsuite/test/api/multiple-targets/main.cpp (added)
+++ lldb/trunk/packages/Python/lldbsuite/test/api/multiple-targets/main.cpp Thu Dec  8 19:21:14 2016
@@ -0,0 +1,31 @@
+#include <thread>
+
+#include "lldb/API/LLDB.h"
+#include "lldb/API/SBDebugger.h"
+#include "lldb/API/SBTarget.h"
+
+using namespace lldb;
+int main (int argc, char **argv)
+{
+  // We are expecting the program path and a path to an executable to load
+  if (argc != 2)
+    return 1;
+  const char *program_file = argv[1];
+  SBDebugger::Initialize();
+  SBDebugger debugger = SBDebugger::Create(false);
+  auto lambda = [&](){
+    SBError error;
+    SBTarget target = debugger.CreateTarget(program_file, nullptr, nullptr, 
+                                            false, error);
+  };
+
+  // Create 3 targets at the same time and make sure we don't crash.
+  std::thread thread1(lambda);
+  std::thread thread2(lambda);
+  std::thread thread3(lambda);
+  thread1.join();
+  thread2.join();
+  thread3.join();
+  SBDebugger::Terminate();
+  return 0;
+}

Modified: lldb/trunk/source/Interpreter/CommandInterpreter.cpp
URL: http://llvm.org/viewvc/llvm-project/lldb/trunk/source/Interpreter/CommandInterpreter.cpp?rev=289169&r1=289168&r2=289169&view=diff
==============================================================================
--- lldb/trunk/source/Interpreter/CommandInterpreter.cpp (original)
+++ lldb/trunk/source/Interpreter/CommandInterpreter.cpp Thu Dec  8 19:21:14 2016
@@ -2477,15 +2477,14 @@ void CommandInterpreter::HandleCommandsF
 }
 
 ScriptInterpreter *CommandInterpreter::GetScriptInterpreter(bool can_create) {
-  if (m_script_interpreter_sp)
-    return m_script_interpreter_sp.get();
-
-  if (!can_create)
-    return nullptr;
-
-  lldb::ScriptLanguage script_lang = GetDebugger().GetScriptLanguage();
-  m_script_interpreter_sp =
-      PluginManager::GetScriptInterpreterForLanguage(script_lang, *this);
+  std::lock_guard<std::mutex> locker(m_script_interpreter_mutex);
+  if (!m_script_interpreter_sp) {
+    if (!can_create)
+      return nullptr;
+    lldb::ScriptLanguage script_lang = GetDebugger().GetScriptLanguage();
+    m_script_interpreter_sp =
+        PluginManager::GetScriptInterpreterForLanguage(script_lang, *this);
+  }
   return m_script_interpreter_sp.get();
 }