Fix a race in ProcessGDBRemote::MonitorDebugServerProcess

Summary:
MonitorDebugServerProcess went to a lot of effort to make sure its asynchronous invocation does
not cause any mischief, but it was still not race-free. Specifically, in a quick stop-restart
sequence (like the one in TestAddressBreakpoints) the copying of the process shared pointer via
target_sp->GetProcessSP() was racing with the resetting of the pointer in DeleteCurrentProcess,
as they were both accessing the same shared_ptr object.

To avoid this, I simply pass in a weak_ptr to the process when the callback is created. Locking
this pointer is race-free as they are two separate object even though they point to the same
process instance. This also removes the need for the complicated tap-dance around retrieving the
process pointer.

Reviewers: clayborg

Subscribers: tberghammer, lldb-commits

Differential Revision: http://reviews.llvm.org/D20107

llvm-svn: 269281

1 files changed, 2 insertions, 1 deletions

diff --git a/lldb/source/Plugins/Process/gdb-remote/ProcessGDBRemote.h b/lldb/source/Plugins/Process/gdb-remote/ProcessGDBRemote.h
index 54d77a5d53a..815435c0f74 100644
--- a/lldb/source/Plugins/Process/gdb-remote/ProcessGDBRemote.h
+++ b/lldb/source/Plugins/Process/gdb-remote/ProcessGDBRemote.h
@@ -405,7 +405,8 @@ protected:
     AsyncThread (void *arg);
 
     static bool
-    MonitorDebugserverProcess(ProcessGDBRemote *process, lldb::pid_t pid, bool exited, int signo, int exit_status);
+    MonitorDebugserverProcess(std::weak_ptr<ProcessGDBRemote> process_wp, lldb::pid_t pid, bool exited, int signo,
+                              int exit_status);
 
     lldb::StateType
     SetThreadStopInfo (StringExtractor& stop_packet);