mpir/pmi: protect 3rd-party pmi from job attributes

Define macro PMI_FROM_3RD_PARTY if linked with a 3rd party pmi
library such as cray, Slurm, and openpmix. They often run into issues
when quieried with nonexistent job attribute keys such as
PMI_process_mapping, PMI_hwloc_pmi, etc.

We have a few patches recently to workaround openpmix with non-existent
job attributes.

Cray PMI used to work, but we encountered a hang with PALS v1.3.4.

This commit skips querying these keys as job attributes to bypass these
potential issues. They are often not supported by 3rd party pmi anyway.

configure.ac

@@ -1661,6 +1661,7 @@ elif test "$with_pmilib" = "default" -o "$with_pmilib" = "mpich" -o "$with_pmili
 fi
 
 if test "$pac_3rd_party_pmi" = "yes" ; then
+    AC_DEFINE([PMI_FROM_3RD_PARTY], 1, [define if PMI is supplied from 3rd party (thus we should limit usage of MPICH extensions)])
     # detect
     PAC_PUSH_FLAG([LIBS])
     LIBS=$WRAPPER_LIBS

src/util/mpir_pmi.c

@@ -315,6 +315,13 @@ int MPIR_pmi_kvs_parent_get(const char *key, char *val, int val_size)
 char *MPIR_pmi_get_jobattr(const char *key)
 {
     char *valbuf = NULL;
+
+#ifdef PMI_FROM_3RD_PARTY
+    /* assume 3rd party pmi (e.g. Cray, Slurm, OpenPMIx) does not support special keys */
+    /* FIXME: add exceptions such as PMI_process_mapping */
+    goto fn_exit;
+#endif
+
     valbuf = MPL_malloc(pmi_max_val_size, MPL_MEM_OTHER);
     if (!valbuf) {
         goto fn_exit;