Index: zorg/buildbot/builders/sanitizers/buildbot_functions.sh
===================================================================
--- zorg/buildbot/builders/sanitizers/buildbot_functions.sh
+++ zorg/buildbot/builders/sanitizers/buildbot_functions.sh
@@ -8,6 +8,9 @@
     svn up "${tree}" $rev_arg
   else
     svn co "${repo}" "${tree}" $rev_arg
+    # checkout will ignore pre-existing and make content look like detede.
+    # Pre-existing dirrectories are possible with concurent execution.
+    svn revert -R "${tree}"
   fi
 }
 
@@ -31,23 +34,24 @@
       fi
     done
 
-    update_or_checkout "$rev_arg" http://llvm.org/svn/llvm-project/llvm/trunk llvm
-
     if [ "$rev_arg" == "" ]; then
-        rev_arg="-r"$(svn info llvm | grep '^Revision:' | awk '{print $2}')
+        rev_arg="-r"$(svn info http://llvm.org/svn/llvm-project/llvm/trunk | grep '^Revision:' | awk '{print $2}')
     fi
 
+    update_or_checkout "$rev_arg" http://llvm.org/svn/llvm-project/llvm/trunk llvm &
+
     # XXX: Keep this list in sync with the change filter in buildbot/osuosl/master/master.cfg.
-    update_or_checkout "$rev_arg" http://llvm.org/svn/llvm-project/cfe/trunk llvm/tools/clang
-    update_or_checkout "$rev_arg" http://llvm.org/svn/llvm-project/compiler-rt/trunk llvm/projects/compiler-rt
+    update_or_checkout "$rev_arg" http://llvm.org/svn/llvm-project/cfe/trunk llvm/tools/clang &
+    update_or_checkout "$rev_arg" http://llvm.org/svn/llvm-project/compiler-rt/trunk llvm/projects/compiler-rt &
     if [ "$CHECK_LIBCXX" != "0" ]; then
-      update_or_checkout "$rev_arg" http://llvm.org/svn/llvm-project/libcxx/trunk llvm/projects/libcxx
-      update_or_checkout "$rev_arg" http://llvm.org/svn/llvm-project/libcxxabi/trunk llvm/projects/libcxxabi
-      update_or_checkout "$rev_arg" http://llvm.org/svn/llvm-project/libunwind/trunk llvm/projects/libunwind
+      update_or_checkout "$rev_arg" http://llvm.org/svn/llvm-project/libcxx/trunk llvm/projects/libcxx &
+      update_or_checkout "$rev_arg" http://llvm.org/svn/llvm-project/libcxxabi/trunk llvm/projects/libcxxabi &
+      update_or_checkout "$rev_arg" http://llvm.org/svn/llvm-project/libunwind/trunk llvm/projects/libunwind &
     fi
     if [ "$CHECK_LLD" != "0" ]; then
-      update_or_checkout "$rev_arg" http://llvm.org/svn/llvm-project/lld/trunk llvm/tools/lld
+      update_or_checkout "$rev_arg" http://llvm.org/svn/llvm-project/lld/trunk llvm/tools/lld &
     fi
+    wait
 }
 
 function set_chrome_suid_sandbox {