diff --git a/include/spdk/io_channel.h b/include/spdk/io_channel.h
index 69f81a4b3..b5fe56c46 100644
--- a/include/spdk/io_channel.h
+++ b/include/spdk/io_channel.h
@@ -45,13 +45,23 @@
 struct spdk_thread;
 struct spdk_io_channel;
 
+typedef void (*spdk_thread_fn)(void *ctx);
+typedef void (*spdk_thread_pass_msg)(spdk_thread_fn fn, void *ctx,
+				     void *thread_ctx);
+
 typedef int (*io_channel_create_cb_t)(void *io_device, void *ctx_buf);
 typedef void (*io_channel_destroy_cb_t)(void *io_device, void *ctx_buf);
 
 /**
  * \brief Initializes the calling thread for I/O channel allocation.
+ *
+ * @param fn A function that may be called from any thread and is
+ *          passed a function pointer (spdk_thread_fn) that must be
+ *          called on the same thread that spdk_allocate_thread
+ *          was called from.
+ * @param thread_ctx Context that will be passed to fn.
  */
-struct spdk_thread *spdk_allocate_thread(void);
+struct spdk_thread *spdk_allocate_thread(spdk_thread_pass_msg fn, void *thread_ctx);
 
 /**
  * \brief Releases any resources related to the calling thread for I/O channel allocation.
@@ -62,10 +72,22 @@ struct spdk_thread *spdk_allocate_thread(void);
 void spdk_free_thread(void);
 
 /**
- * \brief Get a handle to the current thread.
+ * \brief Get a handle to the current thread. This handle may be passed
+ * to other threads and used as the target of spdk_thread_send_msg().
  */
 struct spdk_thread *spdk_get_thread(void);
 
+/**
+ * \brief Send a message to the given thread. The message
+ * may be sent asynchronously - i.e. spdk_thread_send_msg
+ * may return prior to `fn` being called.
+ *
+ * @param thread The target thread.
+ * @param fn This function will be called on the given thread.
+ * @param ctx This context will be passed to fn when called.
+ */
+void spdk_thread_send_msg(const struct spdk_thread *thread, spdk_thread_fn fn, void *ctx);
+
 /**
  * \brief Register the opaque io_device context as an I/O device.
  *
diff --git a/lib/event/reactor.c b/lib/event/reactor.c
index 8e1b6934b..361e81b4f 100644
--- a/lib/event/reactor.c
+++ b/lib/event/reactor.c
@@ -264,6 +264,27 @@ _spdk_poller_unregister_complete(struct spdk_poller *poller)
 	free(poller);
 }
 
+static void
+_spdk_reactor_msg_passed(void *arg1, void *arg2)
+{
+	spdk_thread_fn fn = arg1;
+
+	fn(arg2);
+}
+
+static void
+_spdk_reactor_send_msg(spdk_thread_fn fn, void *ctx, void *thread_ctx)
+{
+	uint32_t core;
+	struct spdk_event *event;
+
+	core = *(uint32_t *)thread_ctx;
+
+	event = spdk_event_allocate(core, _spdk_reactor_msg_passed, fn, ctx);
+
+	spdk_event_call(event);
+}
+
 /**
  *
  * \brief This is the main function of the reactor thread.
@@ -296,7 +317,7 @@ _spdk_reactor_run(void *arg)
 	uint32_t		sleep_us;
 	uint32_t 		timer_poll_count;
 
-	spdk_allocate_thread();
+	spdk_allocate_thread(_spdk_reactor_send_msg, &reactor->lcore);
 	set_reactor_thread_name(reactor->lcore);
 	SPDK_NOTICELOG("Reactor started on core %u on socket %u\n", reactor->lcore,
 		       reactor->socket_id);
diff --git a/lib/util/io_channel.c b/lib/util/io_channel.c
index 7b372cd83..7654ae601 100644
--- a/lib/util/io_channel.c
+++ b/lib/util/io_channel.c
@@ -64,14 +64,18 @@ struct spdk_io_channel {
 };
 
 struct spdk_thread {
+	spdk_thread_pass_msg fn;
+	void *thread_ctx;
 	TAILQ_HEAD(, spdk_io_channel) io_channels;
 };
 
 static __thread struct spdk_thread g_thread;
 
 struct spdk_thread *
-spdk_allocate_thread(void)
+spdk_allocate_thread(spdk_thread_pass_msg fn, void *thread_ctx)
 {
+	g_thread.fn = fn;
+	g_thread.thread_ctx = thread_ctx;
 	TAILQ_INIT(&g_thread.io_channels);
 	return &g_thread;
 }
@@ -88,6 +92,12 @@ spdk_get_thread(void)
 	return &g_thread;
 }
 
+void
+spdk_thread_send_msg(const struct spdk_thread *thread, spdk_thread_fn fn, void *ctx)
+{
+	thread->fn(fn, ctx, thread->thread_ctx);
+}
+
 void
 spdk_io_device_register(void *io_device, io_channel_create_cb_t create_cb,
 			io_channel_destroy_cb_t destroy_cb, uint32_t ctx_size)
diff --git a/test/lib/blob/blob_ut/blob_ut.c b/test/lib/blob/blob_ut/blob_ut.c
index 69b9772f2..52eb4c1f8 100644
--- a/test/lib/blob/blob_ut/blob_ut.c
+++ b/test/lib/blob/blob_ut/blob_ut.c
@@ -48,6 +48,12 @@ int g_bserrno;
 struct spdk_xattr_names *g_names;
 int g_done;
 
+static void
+_bs_send_msg(spdk_thread_fn fn, void *ctx, void *thread_ctx)
+{
+	fn(ctx);
+}
+
 static void
 bs_op_complete(void *cb_arg, int bserrno)
 {
@@ -963,7 +969,7 @@ int main(int argc, char **argv)
 	}
 
 	g_dev_buffer = calloc(1, DEV_BUFFER_SIZE);
-	spdk_allocate_thread();
+	spdk_allocate_thread(_bs_send_msg, NULL);
 	CU_basic_set_mode(CU_BRM_VERBOSE);
 	CU_basic_run_tests();
 	num_failures = CU_get_number_of_failures();
diff --git a/test/lib/blobfs/blobfs_async_ut/blobfs_async_ut.c b/test/lib/blobfs/blobfs_async_ut/blobfs_async_ut.c
index 18c31e617..c678bfb09 100644
--- a/test/lib/blobfs/blobfs_async_ut/blobfs_async_ut.c
+++ b/test/lib/blobfs/blobfs_async_ut/blobfs_async_ut.c
@@ -47,6 +47,12 @@ struct spdk_filesystem *g_fs;
 struct spdk_file *g_file;
 int g_fserrno;
 
+static void
+_fs_send_msg(spdk_thread_fn fn, void *ctx, void *thread_ctx)
+{
+	fn(ctx);
+}
+
 static void
 fs_op_complete(void *ctx, int fserrno)
 {
@@ -67,7 +73,7 @@ fs_init(void)
 	struct spdk_bs_dev dev;
 
 	init_dev(&dev);
-	spdk_allocate_thread();
+	spdk_allocate_thread(_fs_send_msg, NULL);
 
 	spdk_fs_init(&dev, NULL, fs_op_with_handle_complete, NULL);
 	CU_ASSERT(g_fs != NULL);
@@ -109,7 +115,7 @@ fs_open(void)
 	struct spdk_file *file;
 
 	init_dev(&dev);
-	spdk_allocate_thread();
+	spdk_allocate_thread(_fs_send_msg, NULL);
 
 	spdk_fs_init(&dev, NULL, fs_op_with_handle_complete, NULL);
 	CU_ASSERT(g_fs != NULL);
@@ -171,7 +177,7 @@ fs_truncate(void)
 	struct spdk_bs_dev dev;
 
 	init_dev(&dev);
-	spdk_allocate_thread();
+	spdk_allocate_thread(_fs_send_msg, NULL);
 
 	spdk_fs_init(&dev, NULL, fs_op_with_handle_complete, NULL);
 	SPDK_CU_ASSERT_FATAL(g_fs != NULL);
@@ -224,7 +230,7 @@ fs_rename(void)
 	struct spdk_bs_dev dev;
 
 	init_dev(&dev);
-	spdk_allocate_thread();
+	spdk_allocate_thread(_fs_send_msg, NULL);
 
 	spdk_fs_init(&dev, NULL, fs_op_with_handle_complete, NULL);
 	SPDK_CU_ASSERT_FATAL(g_fs != NULL);
@@ -377,7 +383,7 @@ channel_ops(void)
 	struct spdk_io_channel *channel;
 
 	init_dev(&dev);
-	spdk_allocate_thread();
+	spdk_allocate_thread(_fs_send_msg, NULL);
 
 	spdk_fs_init(&dev, NULL, fs_op_with_handle_complete, NULL);
 	SPDK_CU_ASSERT_FATAL(g_fs != NULL);
@@ -405,7 +411,7 @@ channel_ops_sync(void)
 	struct spdk_io_channel *channel;
 
 	init_dev(&dev);
-	spdk_allocate_thread();
+	spdk_allocate_thread(_fs_send_msg, NULL);
 
 	spdk_fs_init(&dev, NULL, fs_op_with_handle_complete, NULL);
 	SPDK_CU_ASSERT_FATAL(g_fs != NULL);
diff --git a/test/lib/blobfs/blobfs_sync_ut/blobfs_sync_ut.c b/test/lib/blobfs/blobfs_sync_ut/blobfs_sync_ut.c
index 09bf3a1fd..432e727a5 100644
--- a/test/lib/blobfs/blobfs_sync_ut/blobfs_sync_ut.c
+++ b/test/lib/blobfs/blobfs_sync_ut/blobfs_sync_ut.c
@@ -51,6 +51,12 @@ int g_fserrno;
 
 struct spdk_bs_dev g_dev;
 
+static void
+_fs_send_msg(spdk_thread_fn fn, void *ctx, void *thread_ctx)
+{
+	fn(ctx);
+}
+
 struct ut_request {
 	fs_request_fn fn;
 	void *arg;
@@ -144,7 +150,7 @@ cache_write(void)
 
 	ut_send_request(_fs_init, NULL);
 
-	spdk_allocate_thread();
+	spdk_allocate_thread(_fs_send_msg, NULL);
 	channel = spdk_fs_alloc_io_channel_sync(g_fs);
 
 	rc = spdk_fs_open_file(g_fs, channel, "testfile", SPDK_BLOBFS_OPEN_CREATE, &g_file);
@@ -182,7 +188,7 @@ cache_write_null_buffer(void)
 
 	ut_send_request(_fs_init, NULL);
 
-	spdk_allocate_thread();
+	spdk_allocate_thread(_fs_send_msg, NULL);
 	channel = spdk_fs_alloc_io_channel_sync(g_fs);
 
 	rc = spdk_fs_open_file(g_fs, channel, "testfile", SPDK_BLOBFS_OPEN_CREATE, &g_file);
@@ -214,7 +220,7 @@ cache_append_no_cache(void)
 
 	ut_send_request(_fs_init, NULL);
 
-	spdk_allocate_thread();
+	spdk_allocate_thread(_fs_send_msg, NULL);
 	channel = spdk_fs_alloc_io_channel_sync(g_fs);
 
 	rc = spdk_fs_open_file(g_fs, channel, "testfile", SPDK_BLOBFS_OPEN_CREATE, &g_file);
@@ -256,7 +262,7 @@ spdk_thread(void *arg)
 {
 	struct ut_request *req;
 
-	spdk_allocate_thread();
+	spdk_allocate_thread(_fs_send_msg, NULL);
 
 	while (1) {
 		pthread_mutex_lock(&g_mutex);
diff --git a/test/lib/util/io_channel/io_channel_ut.c b/test/lib/util/io_channel/io_channel_ut.c
index f0c3e9782..85d15e40d 100644
--- a/test/lib/util/io_channel/io_channel_ut.c
+++ b/test/lib/util/io_channel/io_channel_ut.c
@@ -37,10 +37,16 @@
 
 #include "util/io_channel.c"
 
+static void
+_send_msg(spdk_thread_fn fn, void *ctx, void *thread_ctx)
+{
+	fn(ctx);
+}
+
 static void
 thread_alloc(void)
 {
-	spdk_allocate_thread();
+	spdk_allocate_thread(_send_msg, NULL);
 	spdk_free_thread();
 }
 
@@ -100,7 +106,7 @@ channel(void)
 	struct spdk_io_channel *ch1, *ch2;
 	void *ctx;
 
-	spdk_allocate_thread();
+	spdk_allocate_thread(_send_msg, NULL);
 	spdk_io_device_register(&device1, create_cb_1, destroy_cb_1, sizeof(ctx1));
 	spdk_io_device_register(&device2, create_cb_2, destroy_cb_2, sizeof(ctx2));
 	spdk_io_device_register(&device3, create_cb_null, NULL, 0);