UCX osc: properly release exclusive lock to avoid lockup

Signed-off-by: Joseph Schuchart <schuchart@hlrs.de>
(cherry picked from commit 08cb6389e034c1a70368671f745f20904c774a1e)

ompi/mca/osc/ucx/osc_ucx_passive_target.c

@@ -90,21 +90,19 @@ static inline int start_exclusive(ompi_osc_ucx_module_t *module, int target) {
 }
 
 static inline int end_exclusive(ompi_osc_ucx_module_t *module, int target) {
-    uint64_t result_value = 0;
     ucp_ep_h ep = OSC_UCX_GET_EP(module->comm, target);
     ucp_rkey_h rkey = (module->state_info_array)[target].rkey;
     uint64_t remote_addr = (module->state_info_array)[target].addr + OSC_UCX_STATE_LOCK_OFFSET;
-    int ret;
+    ucs_status_t status;
 
-    ret = opal_common_ucx_atomic_fetch(ep, UCP_ATOMIC_FETCH_OP_SWAP, TARGET_LOCK_UNLOCKED,
-                                       &result_value, sizeof(result_value),
-                                       remote_addr, rkey, mca_osc_ucx_component.ucp_worker);
-    if (OMPI_SUCCESS != ret) {
-        return ret;
+    status = ucp_atomic_post(ep, UCP_ATOMIC_POST_OP_ADD,
+                             -((int64_t)TARGET_LOCK_EXCLUSIVE), sizeof(uint64_t),
+                             remote_addr, rkey);
+    if (UCS_OK != status) {
+        OSC_UCX_VERBOSE(1, "ucp_atomic_post(OP_ADD) failed: %d", status);
+        return OMPI_ERROR;
     }
 
-    assert(result_value >= TARGET_LOCK_EXCLUSIVE);
-
     return OMPI_SUCCESS;
 }