mpi/pmix - defer setting PMIX_USERID

Set PMIX_USERID in pmixp_libpmix_job_set() to notify PMIx to set the
communications socket's owner to the job's user instead of root at this
point in execution.

This patch will only work after pmix commit cbc6d60a00 which it in v5.0.

openpmix/openpmix@cbc6d60a00

Bug 16306

NEWS

@@ -12,6 +12,7 @@ documents those changes that are of interest to users and administrators.
     specification.
  -- scrontab - don't update the cron job tasks if the whole crontab file is
     left untouched after opening it with "scrontab -e".
+ -- mpi/pmix - avoid crashing when running PMIx v5.0 branch with shmem support.
 
 * Changes in Slurm 23.02.1
 ==========================

src/plugins/mpi/pmix/pmixp_client.c

@@ -153,6 +153,16 @@ static void _set_tmpdirs(List lresp)
 	list_append(lresp, kvp);
 }
 
+static void _set_euid(list_t *lresp)
+{
+	pmix_info_t *kvp;
+
+	uid_t uid = pmixp_info_jobuid();
+
+	PMIXP_KVP_CREATE(kvp, PMIX_USERID, &uid, PMIX_UINT32);
+	list_append(lresp, kvp);
+}
+
 /*
  * information about relative ranks as assigned by the RM
  */
@@ -641,6 +651,8 @@ extern int pmixp_libpmix_job_set(void)
 
 	_set_topology(lresp);
 
+	_set_euid(lresp);
+
 	if (SLURM_SUCCESS != _set_mapsinfo(lresp)) {
 		FREE_NULL_LIST(lresp);
 		PMIXP_ERROR("Can't build nodemap");

src/plugins/mpi/pmix/pmixp_client_v2.c

@@ -232,9 +232,6 @@ int pmixp_lib_init(void)
 {
 	pmix_info_t *kvp = NULL;
 	pmix_status_t rc;
-	uint32_t jobuid = pmixp_info_jobuid();
-
-	PMIXP_KVP_ADD(kvp, PMIX_USERID, &jobuid, PMIX_UINT32);
 
 #ifdef PMIX_SERVER_TMPDIR
 	PMIXP_KVP_ADD(kvp, PMIX_SERVER_TMPDIR,