s390/zcrypt: ap bus rescan problem when toggle crypto adapters on/off

The bus rescan process was called simultaneously on
every device failure. This finally leads into race
conditions (double device add/remove actions).

This patch protects the rescan area by mutual exclusion
and improves ap_config_timer handling

Signed-off-by: Ingo Tuchscherer <ingo.tuchscherer@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>

1 files changed, 7 insertions, 10 deletions

diff --git a/drivers/s390/crypto/ap_bus.c b/drivers/s390/crypto/ap_bus.c
index b8b340ac5332..9de41aa14896 100644
--- a/drivers/s390/crypto/ap_bus.c
+++ b/drivers/s390/crypto/ap_bus.c
@@ -954,15 +954,11 @@ EXPORT_SYMBOL(ap_driver_unregister);
 
 void ap_bus_force_rescan(void)
 {
-        /* Delete the AP bus rescan timer. */
-        del_timer(&ap_config_timer);
-
-        /* processing a synchonuous bus rescan */
-        ap_scan_bus(NULL);
-
-        /* Setup the AP bus rescan timer again. */
-        ap_config_timer.expires = jiffies + ap_config_time * HZ;
-        add_timer(&ap_config_timer);
+        /* reconfigure the AP bus rescan timer. */
+        mod_timer(&ap_config_timer, jiffies + ap_config_time * HZ);
+        /* processing a asynchronous bus rescan */
+        queue_work(ap_work_queue, &ap_config_work);
+        flush_work(&ap_config_work);
 }
 EXPORT_SYMBOL(ap_bus_force_rescan);
 
@@ -1305,8 +1301,9 @@ static void ap_scan_bus(struct work_struct *unused)
         int rc, i;
 
         ap_query_configuration();
-        if (ap_select_domain() != 0)
+        if (ap_select_domain() != 0) {
                 return;
+        }
         for (i = 0; i < AP_DEVICES; i++) {
                 qid = AP_MKQID(i, ap_domain_index);
                 dev = bus_find_device(&ap_bus_type, NULL,