Trying to solve our disappearing thread issues by making thread list updates safer.

The current ProcessGDBRemote function that updates the threads could end up with an empty list if any other thread had the sequence mutex. We now don't clear the thread list when we can't access it, and we also have changed how lldb_private::Process handles the return code from the:

virtual bool
Process::UpdateThreadList (lldb_private::ThreadList &old_thread_list, 
                       	   lldb_private::ThreadList &new_thread_list) = 0;

A bool is now returned to indicate if the list was actually updated or not and the lldb_private::Process class will only update the stop ID of the validity of the thread list if "true" is returned.

The ProcessGDBRemote also got an extra assertion that will hopefully assert when running debug builds so we can find the source of this issue.



git-svn-id: https://llvm.org/svn/llvm-project/lldb/trunk@154365 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/source/Plugins/Process/MacOSX-Kernel/ProcessKDP.cpp b/source/Plugins/Process/MacOSX-Kernel/ProcessKDP.cpp
index 1db2d84..45ed9b5 100644
--- a/source/Plugins/Process/MacOSX-Kernel/ProcessKDP.cpp
+++ b/source/Plugins/Process/MacOSX-Kernel/ProcessKDP.cpp
@@ -301,7 +301,7 @@
     return error;
 }
 
-uint32_t
+bool
 ProcessKDP::UpdateThreadList (ThreadList &old_thread_list, ThreadList &new_thread_list)
 {
     // locker will keep a mutex locked until it goes out of scope
@@ -323,7 +323,7 @@
             thread_sp.reset(new ThreadKDP (shared_from_this(), tid));
         new_thread_list.AddThread(thread_sp);
     }
-    return new_thread_list.GetSize(false);
+    return new_thread_list.GetSize(false) > 0;
 }