[Lldb-commits] [PATCH] Fix race condition with -o "process launch" on linux

[Pavel Labath]

Hi jingham, clayborg, vharron,

starting a debug session on linux with -o "process launch" lldb parameter was failing since
Target::Launch (in sychronous mode) is expecting to be able to receive public process events.
However, PlatformLinux did not set up event hijacking on process launch, which caused these
events to be processed elsewhere and left Target::Launch hanging. This patch enables event
interception in PlatformLinux (which was commented out).

Upon enabling event interception, I noticed an issue, which I traced back to the inconsistent
state of public run lock, which remained false even though public and private process states were
"stopped". I addressed this by making sure the run lock is "stopped" upon exit from
WaitForProcessToStop (which already had similar provisions for other return paths).

http://reviews.llvm.org/D8079

Files:
  source/Plugins/Platform/Linux/PlatformLinux.cpp
  source/Target/Process.cpp

Index: source/Plugins/Platform/Linux/PlatformLinux.cpp
===================================================================
--- source/Plugins/Platform/Linux/PlatformLinux.cpp
+++ source/Plugins/Platform/Linux/PlatformLinux.cpp
@@ -765,7 +765,6 @@
 
     // Adjust launch for a hijacker.
     ListenerSP listener_sp;
-#if 0
     if (!launch_info.GetHijackListener ())
     {
         if (log)
@@ -775,7 +774,6 @@
         launch_info.SetHijackListener (listener_sp);
         process_sp->HijackProcessEvents (listener_sp.get ());
     }
-#endif
 
     // Log file actions.
     if (log)
@@ -801,7 +799,6 @@
         if (listener_sp)
         {
             const StateType state = process_sp->WaitForProcessToStop (NULL, NULL, false, listener_sp.get());
-            process_sp->RestoreProcessEvents();
 
             if (state == eStateStopped)
             {
Index: source/Target/Process.cpp
===================================================================
--- source/Target/Process.cpp
+++ source/Target/Process.cpp
@@ -1011,6 +1011,10 @@
         if (log)
             log->Printf("Process::%s returning without waiting for events; process private and public states are already 'stopped'.",
                         __FUNCTION__);
+        // We need to toggle the run lock as this won't get done in
+        // SetPublicState() if the process is hijacked.
+        if (hijack_listener)
+            m_public_run_lock.SetStopped();
         return state;
     }

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