[Lldb-commits] [lldb] 1f5f416 - [lldb] Fix dead lock issue when loading modules in Scripted Process

[Med Ismail Bennani via lldb-commits]

Author: Med Ismail Bennani
Date: 2023-07-06T14:33:52-07:00
New Revision: 1f5f4169c427c51c6919e0013c89a191dba564e8

URL: https://github.com/llvm/llvm-project/commit/1f5f4169c427c51c6919e0013c89a191dba564e8
DIFF: https://github.com/llvm/llvm-project/commit/1f5f4169c427c51c6919e0013c89a191dba564e8.diff

LOG: [lldb] Fix dead lock issue when loading modules in Scripted Process

This patch attempts to fix a dead lock when loading modules in a Scripted
Process.

This issue was triggered by loading the modules after the process did resume,
but before the process actually stop, causing the language runtime mutex to
be locked by a separate thread, responsible to unwind the stack (using
the runtime unwind plan), while the module loading thread was trying to
notify the runtimes of the newly loaded module.

To address that, this patch moves the module loading logic to be done before
sending the stop event, to prevent the dead lock situation described above.

Differential Revision: https://reviews.llvm.org/D154649

Signed-off-by: Med Ismail Bennani <ismail at bennani.ma>

Added: 
    

Modified: 
    lldb/source/Plugins/Process/scripted/ScriptedProcess.cpp
    lldb/source/Plugins/Process/scripted/ScriptedProcess.h

Removed: 
    


################################################################################
diff  --git a/lldb/source/Plugins/Process/scripted/ScriptedProcess.cpp b/lldb/source/Plugins/Process/scripted/ScriptedProcess.cpp
index 5be1eff76ba9da..e99a2a08bd50d8 100644
--- a/lldb/source/Plugins/Process/scripted/ScriptedProcess.cpp
+++ b/lldb/source/Plugins/Process/scripted/ScriptedProcess.cpp
@@ -166,7 +166,6 @@ void ScriptedProcess::DidLaunch() { m_pid = GetInterface().GetProcessID(); }
 void ScriptedProcess::DidResume() {
   // Update the PID again, in case the user provided a placeholder pid at launch
   m_pid = GetInterface().GetProcessID();
-  GetLoadedDynamicLibrariesInfos();
 }
 
 Status ScriptedProcess::DoResume() {

diff  --git a/lldb/source/Plugins/Process/scripted/ScriptedProcess.h b/lldb/source/Plugins/Process/scripted/ScriptedProcess.h
index 24b5a317b54fa8..0335364b4010b2 100644
--- a/lldb/source/Plugins/Process/scripted/ScriptedProcess.h
+++ b/lldb/source/Plugins/Process/scripted/ScriptedProcess.h
@@ -12,6 +12,7 @@
 #include "lldb/Target/Process.h"
 #include "lldb/Utility/ConstString.h"
 #include "lldb/Utility/ScriptedMetadata.h"
+#include "lldb/Utility/State.h"
 #include "lldb/Utility/Status.h"
 
 #include "ScriptedThread.h"
@@ -93,6 +94,11 @@ class ScriptedProcess : public Process {
   void *GetImplementation() override;
 
   void ForceScriptedState(lldb::StateType state) override {
+    // If we're about to stop, we should fetch the loaded dynamic libraries
+    // dictionary before emitting the private stop event to avoid having the
+    // module loading happen while the process state is changing.
+    if (StateIsStoppedState(state, true))
+      GetLoadedDynamicLibrariesInfos();
     SetPrivateState(state);
   }