SERVER-9333 correct reference counting of GhostSlave members

The _ghostCache contains shared pointers to GhostSlave members.
When we clear this cache, we decrement all the reference counts to these objects.
Because we were not keeping a shared_ptr to a GhostSlave object in percolate(),
but instead were using a bare pointer, this caused the bare pointer to be deleted
out from under us when we cleared the cache.  This in turn caused the internal
objects like the OplogReader to be deleted, which caused segfaults in percolate()
when we attempted to advance the oplogreader cursor.

1 files changed, 2 insertions, 3 deletions

diff --git a/src/mongo/db/repl/rs_sync.cpp b/src/mongo/db/repl/rs_sync.cpp
index 548b646c342..4970650d7e8 100644
--- a/src/mongo/db/repl/rs_sync.cpp
+++ b/src/mongo/db/repl/rs_sync.cpp
@@ -832,7 +832,7 @@ namespace replset {
 
     void GhostSync::percolate(const BSONObj& id, const OpTime& last) {
         const OID rid = id["_id"].OID();
-        GhostSlave* slave;
+        shared_ptr<GhostSlave> slave;
         {
             rwlock lk( _lock , false );
 
@@ -842,13 +842,12 @@ namespace replset {
                 return;
             }
 
-            slave = i->second.get();
+            slave = i->second;
             if (!slave->init) {
                 OCCASIONALLY log() << "couldn't percolate slave " << rid << " not init" << rsLog;
                 return;
             }
         }
-
         verify(slave->slave);
 
         const Member *target = replset::BackgroundSync::get()->getSyncTarget();