diff --git a/lib/nvme/nvme.c b/lib/nvme/nvme.c
index 41af20fc2..dcbe85d29 100644
--- a/lib/nvme/nvme.c
+++ b/lib/nvme/nvme.c
@@ -62,8 +62,12 @@ spdk_nvme_detach(struct spdk_nvme_ctrlr *ctrlr)
 {
 	pthread_mutex_lock(&g_spdk_nvme_driver->lock);
 
-	TAILQ_REMOVE(&g_spdk_nvme_driver->attached_ctrlrs, ctrlr, tailq);
-	nvme_ctrlr_destruct(ctrlr);
+	nvme_ctrlr_proc_put_ref(ctrlr);
+
+	if (nvme_ctrlr_get_ref_count(ctrlr) == 0) {
+		TAILQ_REMOVE(&g_spdk_nvme_driver->attached_ctrlrs, ctrlr, tailq);
+		nvme_ctrlr_destruct(ctrlr);
+	}
 
 	pthread_mutex_unlock(&g_spdk_nvme_driver->lock);
 	return 0;
@@ -326,6 +330,12 @@ spdk_nvme_probe(void *cb_ctx, spdk_nvme_probe_cb probe_cb, spdk_nvme_attach_cb a
 				TAILQ_REMOVE(&g_spdk_nvme_driver->init_ctrlrs, ctrlr, tailq);
 				TAILQ_INSERT_TAIL(&g_spdk_nvme_driver->attached_ctrlrs, ctrlr, tailq);
 
+				/*
+				 * Increase the ref count before calling attach_cb() as the user may
+				 * call nvme_detach() immediately.
+				 */
+				nvme_ctrlr_proc_get_ref(ctrlr);
+
 				/*
 				 * Unlock while calling attach_cb() so the user can call other functions
 				 *  that may take the driver lock, like nvme_detach().
diff --git a/lib/nvme/nvme_ctrlr.c b/lib/nvme/nvme_ctrlr.c
index ed5e56937..a5d0074bd 100644
--- a/lib/nvme/nvme_ctrlr.c
+++ b/lib/nvme/nvme_ctrlr.c
@@ -33,6 +33,7 @@
 
 #include "nvme_internal.h"
 #include "spdk/env.h"
+#include <signal.h>
 
 static int nvme_ctrlr_construct_and_submit_aer(struct spdk_nvme_ctrlr *ctrlr,
 		struct nvme_async_event_request *aer);
@@ -822,12 +823,34 @@ nvme_ctrlr_add_process(struct spdk_nvme_ctrlr *ctrlr, void *devhandle)
 	ctrlr_proc->pid = getpid();
 	STAILQ_INIT(&ctrlr_proc->active_reqs);
 	ctrlr_proc->devhandle = devhandle;
+	ctrlr_proc->ref = 0;
 
 	TAILQ_INSERT_TAIL(&ctrlr->active_procs, ctrlr_proc, tailq);
 
 	return 0;
 }
 
+/**
+ * This function will be called when the process exited unexpectedly
+ *  in order to free any incomplete nvme request and allocated memory.
+ * Note: the ctrl_lock must be held when calling this function.
+ */
+static void
+nvme_ctrlr_cleanup_process(struct spdk_nvme_controller_process *proc)
+{
+	struct nvme_request	*req, *tmp_req;
+
+	STAILQ_FOREACH_SAFE(req, &proc->active_reqs, stailq, tmp_req) {
+		STAILQ_REMOVE(&proc->active_reqs, req, nvme_request, stailq);
+
+		assert(req->pid == proc->pid);
+
+		nvme_free_request(req);
+	}
+
+	spdk_free(proc);
+}
+
 /**
  * This function will be called when destructing the controller.
  *  1. There is no more admin request on this controller.
@@ -848,6 +871,88 @@ nvme_ctrlr_free_processes(struct spdk_nvme_ctrlr *ctrlr)
 	}
 }
 
+/**
+ * This function will be called when any other process attaches or
+ *  detaches the controller in order to cleanup those unexpectedly
+ *  terminated processes.
+ * Note: the ctrl_lock must be held when calling this function.
+ */
+static void
+nvme_ctrlr_remove_inactive_proc(struct spdk_nvme_ctrlr *ctrlr)
+{
+	struct spdk_nvme_controller_process	*active_proc, *tmp;
+
+	TAILQ_FOREACH_SAFE(active_proc, &ctrlr->active_procs, tailq, tmp) {
+		if ((kill(active_proc->pid, 0) == -1) && (errno == ESRCH)) {
+			SPDK_ERRLOG("process %d terminated unexpected\n", active_proc->pid);
+
+			TAILQ_REMOVE(&ctrlr->active_procs, active_proc, tailq);
+
+			nvme_ctrlr_cleanup_process(active_proc);
+		}
+	}
+}
+
+void
+nvme_ctrlr_proc_get_ref(struct spdk_nvme_ctrlr *ctrlr)
+{
+	struct spdk_nvme_controller_process	*active_proc;
+	pid_t					pid = getpid();
+
+	pthread_mutex_lock(&ctrlr->ctrlr_lock);
+
+	nvme_ctrlr_remove_inactive_proc(ctrlr);
+
+	TAILQ_FOREACH(active_proc, &ctrlr->active_procs, tailq) {
+		if (active_proc->pid == pid) {
+			active_proc->ref++;
+			break;
+		}
+	}
+
+	pthread_mutex_unlock(&ctrlr->ctrlr_lock);
+}
+
+void
+nvme_ctrlr_proc_put_ref(struct spdk_nvme_ctrlr *ctrlr)
+{
+	struct spdk_nvme_controller_process	*active_proc;
+	pid_t					pid = getpid();
+
+	pthread_mutex_lock(&ctrlr->ctrlr_lock);
+
+	nvme_ctrlr_remove_inactive_proc(ctrlr);
+
+	TAILQ_FOREACH(active_proc, &ctrlr->active_procs, tailq) {
+		if (active_proc->pid == pid) {
+			active_proc->ref--;
+			assert(active_proc->ref >= 0);
+			break;
+		}
+	}
+
+	pthread_mutex_unlock(&ctrlr->ctrlr_lock);
+}
+
+int
+nvme_ctrlr_get_ref_count(struct spdk_nvme_ctrlr *ctrlr)
+{
+	struct spdk_nvme_controller_process	*active_proc;
+	int					ref = 0;
+
+	pthread_mutex_lock(&ctrlr->ctrlr_lock);
+
+	nvme_ctrlr_remove_inactive_proc(ctrlr);
+
+	TAILQ_FOREACH(active_proc, &ctrlr->active_procs, tailq) {
+		ref += active_proc->ref;
+	}
+
+	pthread_mutex_unlock(&ctrlr->ctrlr_lock);
+
+	return ref;
+}
+
 /**
  * This function will be called repeatedly during initialization until the controller is ready.
  */
diff --git a/lib/nvme/nvme_internal.h b/lib/nvme/nvme_internal.h
index c8a8cfa72..57ba25926 100644
--- a/lib/nvme/nvme_internal.h
+++ b/lib/nvme/nvme_internal.h
@@ -310,6 +310,9 @@ struct spdk_nvme_controller_process {
 
 	/** Per process PCI device handle */
 	struct spdk_pci_device				*devhandle;
+
+	/** Reference to track the number of attachment to this controller. */
+	int						ref;
 };
 
 /*
@@ -548,4 +551,14 @@ DECLARE_TRANSPORT(pcie)
 
 #undef DECLARE_TRANSPORT
 
+/*
+ * Below ref related functions must be called with the global
+ *  driver lock held for the multi-process condition.
+ *  Within these functions, the per ctrlr ctrlr_lock is also
+ *  acquired for the multi-thread condition.
+ */
+void	nvme_ctrlr_proc_get_ref(struct spdk_nvme_ctrlr *ctrlr);
+void	nvme_ctrlr_proc_put_ref(struct spdk_nvme_ctrlr *ctrlr);
+int	nvme_ctrlr_get_ref_count(struct spdk_nvme_ctrlr *ctrlr);
+
 #endif /* __NVME_INTERNAL_H__ */
diff --git a/test/lib/nvme/unit/nvme_c/nvme_ut.c b/test/lib/nvme/unit/nvme_c/nvme_ut.c
index 000c8dc06..fa6ab8996 100644
--- a/test/lib/nvme/unit/nvme_c/nvme_ut.c
+++ b/test/lib/nvme/unit/nvme_c/nvme_ut.c
@@ -107,6 +107,24 @@ spdk_pci_addr_compare(const struct spdk_pci_addr *a1, const struct spdk_pci_addr
 	return true;
 }
 
+void
+nvme_ctrlr_proc_get_ref(struct spdk_nvme_ctrlr *ctrlr)
+{
+	return;
+}
+
+void
+nvme_ctrlr_proc_put_ref(struct spdk_nvme_ctrlr *ctrlr)
+{
+	return;
+}
+
+int
+nvme_ctrlr_get_ref_count(struct spdk_nvme_ctrlr *ctrlr)
+{
+	return 0;
+}
+
 static void
 test_opc_data_transfer(void)
 {
diff --git a/test/lib/nvme/unit/nvme_ctrlr_c/nvme_ctrlr_ut.c b/test/lib/nvme/unit/nvme_ctrlr_c/nvme_ctrlr_ut.c
index 56f6bbc0f..763dd5b5f 100644
--- a/test/lib/nvme/unit/nvme_ctrlr_c/nvme_ctrlr_ut.c
+++ b/test/lib/nvme/unit/nvme_ctrlr_c/nvme_ctrlr_ut.c
@@ -388,6 +388,12 @@ nvme_allocate_request_null(spdk_nvme_cmd_cb cb_fn, void *cb_arg)
 	return nvme_allocate_request_contig(NULL, 0, cb_fn, cb_arg);
 }
 
+void
+nvme_free_request(struct nvme_request *req)
+{
+	spdk_mempool_put(_g_nvme_driver.request_mempool, req);
+}
+
 static void
 test_nvme_ctrlr_init_en_1_rdy_0(void)
 {
diff --git a/test/lib/nvme/unit/nvme_ns_cmd_c/nvme_ns_cmd_ut.c b/test/lib/nvme/unit/nvme_ns_cmd_c/nvme_ns_cmd_ut.c
index e911fa34d..a9ff1966f 100644
--- a/test/lib/nvme/unit/nvme_ns_cmd_c/nvme_ns_cmd_ut.c
+++ b/test/lib/nvme/unit/nvme_ns_cmd_c/nvme_ns_cmd_ut.c
@@ -136,6 +136,24 @@ nvme_qpair_submit_request(struct spdk_nvme_qpair *qpair, struct nvme_request *re
 	return 0;
 }
 
+void
+nvme_ctrlr_proc_get_ref(struct spdk_nvme_ctrlr *ctrlr)
+{
+	return;
+}
+
+void
+nvme_ctrlr_proc_put_ref(struct spdk_nvme_ctrlr *ctrlr)
+{
+	return;
+}
+
+int
+nvme_ctrlr_get_ref_count(struct spdk_nvme_ctrlr *ctrlr)
+{
+	return 0;
+}
+
 static void
 prepare_for_test(struct spdk_nvme_ns *ns, struct spdk_nvme_ctrlr *ctrlr,
 		 struct spdk_nvme_qpair *qpair,