diff --git a/openbsc/include/openbsc/gprs_sgsn.h b/openbsc/include/openbsc/gprs_sgsn.h
index 2b94096..d6a9bda 100644
--- a/openbsc/include/openbsc/gprs_sgsn.h
+++ b/openbsc/include/openbsc/gprs_sgsn.h
@@ -271,6 +271,13 @@
 	char imsi[16+1];
 };
 
+enum sgsn_subscriber_proc {
+	SGSN_SUBSCR_PROC_NONE = 0,
+	SGSN_SUBSCR_PROC_PURGE,
+	SGSN_SUBSCR_PROC_UPD_LOC,
+	SGSN_SUBSCR_PROC_UPD_AUTH,
+};
+
 struct sgsn_subscriber_data {
 	struct sgsn_mm_ctx	*mm;
 	struct gsm_auth_tuple	auth_triplets[5];
@@ -278,6 +285,7 @@
 	int			error_cause;
 	struct osmo_timer_list	timer;
 	int			retries;
+	enum sgsn_subscriber_proc blocked_by;
 };
 
 #define LOGGSUBSCRP(level, subscr, fmt, args...) \
@@ -324,6 +332,10 @@
 void gprs_subscr_update_auth_info(struct gsm_subscriber *subscr);
 int gprs_subscr_rx_gsup_message(struct msgb *msg);
 
+int gprs_subscr_purge(struct gsm_subscriber *subscr);
+int gprs_subscr_query_auth_info(struct gsm_subscriber *subscr);
+int gprs_subscr_location_update(struct gsm_subscriber *subscr);
+
 /* Called on subscriber data updates */
 void sgsn_update_subscriber_data(struct sgsn_mm_ctx *mmctx,
 				 struct gsm_subscriber *subscr);
diff --git a/openbsc/src/gprs/gprs_subscriber.c b/openbsc/src/gprs/gprs_subscriber.c
index 8399ea1..88e037e 100644
--- a/openbsc/src/gprs/gprs_subscriber.c
+++ b/openbsc/src/gprs/gprs_subscriber.c
@@ -76,6 +76,23 @@
 	return rc;
 }
 
+static int check_blocking(
+	struct gsm_subscriber *subscr,
+	enum sgsn_subscriber_proc what)
+{
+	if (subscr->sgsn_data->blocked_by == SGSN_SUBSCR_PROC_NONE ||
+	    subscr->sgsn_data->blocked_by == what)
+		return 1;
+
+	return 0;
+}
+
+static void abort_blocking_procedure(struct gsm_subscriber *subscr)
+{
+	/* Best effort, stop retries at least */
+	subscr->sgsn_data->retries = SGSN_SUBSCR_MAX_RETRIES;
+}
+
 static void sgsn_subscriber_timeout_cb(void *subscr_);
 int gprs_subscr_purge(struct gsm_subscriber *subscr);
 
@@ -132,6 +149,10 @@
 	return;
 
 force_cleanup:
+	/* Make sure to clear blocking */
+	if (check_blocking(subscr, SGSN_SUBSCR_PROC_PURGE))
+		subscr->sgsn_data->blocked_by = SGSN_SUBSCR_PROC_NONE;
+
 	/* Make sure, the timer is cleaned up */
 	subscr->keep_in_ram = 0;
 	gprs_subscr_stop_timer(subscr);
@@ -544,17 +565,42 @@
 int gprs_subscr_purge(struct gsm_subscriber *subscr)
 {
 	struct gprs_gsup_message gsup_msg = {0};
+	int rc;
+
+	if (!check_blocking(subscr, SGSN_SUBSCR_PROC_PURGE)) {
+		LOGGSUBSCRP(
+			LOGL_NOTICE, subscr,
+			"Cannot purge MS subscriber, blocked\n");
+		return -EAGAIN;
+	}
+
+	/* GSM 09.02, 19.4.1.4 requires other MAP requests to be blocked until
+	 * this procedure is completed
+	 */
+	subscr->sgsn_data->blocked_by = SGSN_SUBSCR_PROC_PURGE;
 
 	LOGGSUBSCRP(LOGL_INFO, subscr, "purging MS subscriber\n");
 
 	gsup_msg.message_type = GPRS_GSUP_MSGT_PURGE_MS_REQUEST;
-	return gprs_subscr_tx_gsup_message(subscr, &gsup_msg);
+	rc = gprs_subscr_tx_gsup_message(subscr, &gsup_msg);
+	if (rc < 0)
+		subscr->sgsn_data->blocked_by = SGSN_SUBSCR_PROC_NONE;
+
+	return rc;
 }
 
 int gprs_subscr_query_auth_info(struct gsm_subscriber *subscr)
 {
 	struct gprs_gsup_message gsup_msg = {0};
 
+	if (!check_blocking(subscr, SGSN_SUBSCR_PROC_UPD_AUTH)) {
+		LOGGSUBSCRP(
+			LOGL_NOTICE, subscr,
+			"Cannot start update auth info request procedure, blocked\n");
+		abort_blocking_procedure(subscr);
+		return -EAGAIN;
+	}
+
 	LOGGSUBSCRP(LOGL_INFO, subscr,
 		"subscriber auth info is not available\n");
 
@@ -566,6 +612,14 @@
 {
 	struct gprs_gsup_message gsup_msg = {0};
 
+	if (!check_blocking(subscr, SGSN_SUBSCR_PROC_UPD_LOC)) {
+		LOGGSUBSCRP(
+			LOGL_NOTICE, subscr,
+			"Cannot start update location procedure, blocked\n");
+		abort_blocking_procedure(subscr);
+		return -EAGAIN;
+	}
+
 	LOGGSUBSCRP(LOGL_INFO, subscr,
 		"subscriber data is not available\n");
 
diff --git a/openbsc/tests/sgsn/sgsn_test.c b/openbsc/tests/sgsn/sgsn_test.c
index 8181061..d419f0a 100644
--- a/openbsc/tests/sgsn/sgsn_test.c
+++ b/openbsc/tests/sgsn/sgsn_test.c
@@ -546,6 +546,97 @@
 	update_subscriber_data_cb = __real_sgsn_update_subscriber_data;
 }
 
+int my_gprs_gsup_client_send_dummy(struct gprs_gsup_client *gsupc, struct msgb *msg)
+{
+	msgb_free(msg);
+	return 0;
+};
+
+
+static void test_subscriber_blocking(void)
+{
+	struct gsm_subscriber *s1;
+	const char *imsi1 = "1234567890";
+	struct sgsn_mm_ctx *ctx;
+	struct gprs_ra_id raid = { 0, };
+	uint32_t local_tlli = 0xffeeddcc;
+	struct gprs_llc_llme *llme;
+	int rc;
+
+	printf("Testing subcriber procedure blocking\n");
+
+	gprs_gsup_client_send_cb = my_gprs_gsup_client_send_dummy;
+	sgsn->gsup_client = talloc_zero(tall_bsc_ctx, struct gprs_gsup_client);
+
+	/* Check for emptiness */
+	OSMO_ASSERT(gprs_subscr_get_by_imsi(imsi1) == NULL);
+
+	/* Create a context */
+	OSMO_ASSERT(count(gprs_llme_list()) == 0);
+	ctx = alloc_mm_ctx(local_tlli, &raid);
+	llme = ctx->llme;
+	strncpy(ctx->imsi, imsi1, sizeof(ctx->imsi) - 1);
+
+	/* Allocate and attach a subscriber */
+	s1 = gprs_subscr_get_or_create_by_mmctx(ctx);
+	assert_subscr(s1, imsi1);
+
+	/* Start SendAuthInfoRequest procedure */
+	rc = gprs_subscr_query_auth_info(s1);
+	/* Not blocking */
+	OSMO_ASSERT(rc == 0);
+
+	/* Start UpdateLocation procedure */
+	rc = gprs_subscr_location_update(s1);
+	/* Blocking */
+	OSMO_ASSERT(rc == 0);
+
+	/* Start PurgeMS procedure */
+	rc = gprs_subscr_purge(s1);
+	/* Not blocking */
+	OSMO_ASSERT(rc == 0);
+	OSMO_ASSERT(s1->sgsn_data->blocked_by == SGSN_SUBSCR_PROC_PURGE);
+
+	/* Start PurgeMS procedure (retry) */
+	rc = gprs_subscr_purge(s1);
+	/* Not blocking */
+	OSMO_ASSERT(rc == 0);
+
+	/* Start SendAuthInfoRequest procedure */
+	rc = gprs_subscr_query_auth_info(s1);
+	/* Blocking */
+	OSMO_ASSERT(rc == -EAGAIN);
+
+	/* Start UpdateLocation procedure */
+	rc = gprs_subscr_location_update(s1);
+	/* Blocking */
+	OSMO_ASSERT(rc == -EAGAIN);
+
+	/* Unblock manually (normally done by the caller of gprs_subscr_purge) */
+	s1->sgsn_data->blocked_by = SGSN_SUBSCR_PROC_NONE;
+
+	/* Start SendAuthInfoRequest procedure */
+	rc = gprs_subscr_query_auth_info(s1);
+	/* Not blocking */
+	OSMO_ASSERT(rc == 0);
+
+	/* Start UpdateLocation procedure */
+	rc = gprs_subscr_location_update(s1);
+	/* Blocking */
+	OSMO_ASSERT(rc == 0);
+
+	subscr_put(s1);
+	sgsn_mm_ctx_free(ctx);
+	gprs_llgmm_assign(llme, local_tlli, 0xffffffff, GPRS_ALGO_GEA0, NULL);
+
+	assert_no_subscrs();
+
+	gprs_gsup_client_send_cb = __real_gprs_gsup_client_send;
+	talloc_free(sgsn->gsup_client);
+	sgsn->gsup_client = NULL;
+}
+
+
 /*
  * Test that a GMM Detach will remove the MMCTX and the
  * associated LLME.
@@ -1710,6 +1801,7 @@
 	test_subscriber();
 	test_auth_triplets();
 	test_subscriber_gsup();
+	test_subscriber_blocking();
 	test_gmm_detach();
 	test_gmm_detach_power_off();
 	test_gmm_detach_no_mmctx();
diff --git a/openbsc/tests/sgsn/sgsn_test.ok b/openbsc/tests/sgsn/sgsn_test.ok
index cff2920..e5df504 100644
--- a/openbsc/tests/sgsn/sgsn_test.ok
+++ b/openbsc/tests/sgsn/sgsn_test.ok
@@ -2,6 +2,7 @@
 Testing core subscriber data API
 Testing authentication triplet handling
 Testing subcriber GSUP handling
+Testing subcriber procedure blocking
 Testing GMM detach
 Testing GMM detach (power off)
 Testing GMM detach (no MMCTX)