ch4/posix: use static shm_limit_counter

current main branch sets MPIDI_POSIX_shm_limit_counter as MPIDI_POSIX_global.shm_ptr,
which is to record total amount of shm mem used in coll calls. However, during
finalize stage, MPIDI_POSIX_global will be freed first and the following operations
on MPIDI_POSIX_shm_limit_counter will be invalid and cause memory segmentation fault.
This commit makes MPIDI_POSIX_shm_limit_counter point to global variable and avoid
considering the finalize sequence.

src/mpid/ch4/shm/posix/globals.c

@@ -11,3 +11,4 @@ MPIDI_POSIX_global_t MPIDI_POSIX_global = { 0 };
 MPIDI_POSIX_eager_funcs_t *MPIDI_POSIX_eager_func = NULL;
 
 MPL_atomic_uint64_t *MPIDI_POSIX_shm_limit_counter = NULL;
+MPL_atomic_uint64_t MPIDI_POSIX_global_shm_ptr;

src/mpid/ch4/shm/posix/posix_init.c

@@ -40,6 +40,7 @@
 #include "mpidu_genq.h"
 
 extern MPL_atomic_uint64_t *MPIDI_POSIX_shm_limit_counter;
+extern MPL_atomic_uint64_t MPIDI_POSIX_global_shm_ptr;
 
 static int choose_posix_eager(void);
 static void *host_alloc(uintptr_t size);
@@ -235,14 +236,7 @@ int MPIDI_POSIX_coll_init(int rank, int size)
     }
     MPIR_ERR_CHECK(mpi_errno);
 
-    /* Actually allocate the segment and assign regions to the pointers */
-    mpi_errno = MPIDU_Init_shm_alloc(sizeof(int), &MPIDI_POSIX_global.shm_ptr);
-    MPIR_ERR_CHECK(mpi_errno);
-
-    MPIDI_POSIX_shm_limit_counter = (MPL_atomic_uint64_t *) MPIDI_POSIX_global.shm_ptr;
-
-    mpi_errno = MPIDU_Init_shm_barrier();
-    MPIR_ERR_CHECK(mpi_errno);
+    MPIDI_POSIX_shm_limit_counter = &MPIDI_POSIX_global_shm_ptr;
 
     /* Set the counter to 0 */
     MPL_atomic_relaxed_store_uint64(MPIDI_POSIX_shm_limit_counter, 0);
@@ -261,10 +255,6 @@ int MPIDI_POSIX_coll_finalize(void)
     MPIR_FUNC_VERBOSE_STATE_DECL(MPID_STATE_MPIDI_POSIX_COLL_FINALIZE);
     MPIR_FUNC_VERBOSE_ENTER(MPID_STATE_MPIDI_POSIX_COLL_FINALIZE);
 
-    /* Destroy the shared counter which was used to track the amount of shared memory created
-     * per node for intra-node collectives */
-    mpi_errno = MPIDU_Init_shm_free(MPIDI_POSIX_global.shm_ptr);
-
     if (MPIDI_global.shm.posix.csel_root) {
         mpi_errno = MPIR_Csel_free(MPIDI_global.shm.posix.csel_root);
         MPIR_ERR_CHECK(mpi_errno);

src/mpid/ch4/shm/posix/posix_types.h

@@ -34,8 +34,6 @@ typedef struct {
     /* Active recv requests array */
     MPIR_Request **active_rreq;
 
-    void *shm_ptr;
-
     /* Keep track of all of the local processes in MPI_COMM_WORLD and what their original rank was
      * in that communicator. */
     int num_local;