fix: detect threading model to take appropriate flow in mxm

This commit was SVN r28648.

ompi/mca/mtl/mxm/mtl_mxm_component.c

@@ -12,6 +12,7 @@
 #include "opal/util/output.h"
 #include "ompi/proc/proc.h"
 #include "opal/memoryhooks/memory.h"
+#include "ompi/runtime/mpiruntime.h"
 
 #include "mtl_mxm.h"
 #include "mtl_mxm_types.h"
@@ -122,6 +123,7 @@ static int ompi_mtl_mxm_component_open(void)
         MXM_VERBOSE(1, "Disabling on-demand memory mapping");
         ompi_mtl_mxm.using_mem_hooks = 0;
     }
+    setenv("MXM_SINGLE_THREAD", ompi_mpi_thread_multiple ? "n" : "y" , 0);
 #endif
 
     err = mxm_config_read_context_opts(&ompi_mtl_mxm.mxm_opts);