s390/zcrypt: get rid of ap_poll_requests

The poll thread of the AP bus is burning CPU while waiting for
crypto requests to complete. We can as well burn a few more cycles
in the poll thread to check if there are pending requests and
remove the atomic operations with the ap_poll_requests.
This improves the code if the machine has adapter interrupts.

Signed-off-by: Harald Freudenberger <freude@linux.vnet.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>

1 files changed, 24 insertions, 10 deletions

diff --git a/drivers/s390/crypto/ap_bus.c b/drivers/s390/crypto/ap_bus.c
index f6de22a4f7d9..fe1cfa4b22c9 100644
--- a/drivers/s390/crypto/ap_bus.c
+++ b/drivers/s390/crypto/ap_bus.c
@@ -91,7 +91,6 @@ static DECLARE_WORK(ap_scan_work, ap_scan_bus);
  */
 static void ap_tasklet_fn(unsigned long);
 static DECLARE_TASKLET(ap_tasklet, ap_tasklet_fn, 0);
-static atomic_t ap_poll_requests = ATOMIC_INIT(0);
 static DECLARE_WAIT_QUEUE_HEAD(ap_poll_wait);
 static struct task_struct *ap_poll_kthread = NULL;
 static DEFINE_MUTEX(ap_poll_thread_mutex);
@@ -419,7 +418,6 @@ static struct ap_queue_status ap_sm_recv(struct ap_device *ap_dev)
                          ap_dev->reply->message, ap_dev->reply->length);
         switch (status.response_code) {
         case AP_RESPONSE_NORMAL:
-                atomic_dec(&ap_poll_requests);
                 ap_dev->queue_count--;
                 if (ap_dev->queue_count > 0)
                         mod_timer(&ap_dev->timeout,
@@ -436,7 +434,6 @@ static struct ap_queue_status ap_sm_recv(struct ap_device *ap_dev)
                 if (!status.queue_empty || ap_dev->queue_count <= 0)
                         break;
                 /* The card shouldn't forget requests but who knows. */
-                atomic_sub(ap_dev->queue_count, &ap_poll_requests);
                 ap_dev->queue_count = 0;
                 list_splice_init(&ap_dev->pendingq, &ap_dev->requestq);
                 ap_dev->requestq_count += ap_dev->pendingq_count;
@@ -524,7 +521,6 @@ static enum ap_wait ap_sm_write(struct ap_device *ap_dev)
                            ap_msg->message, ap_msg->length, ap_msg->special);
         switch (status.response_code) {
         case AP_RESPONSE_NORMAL:
-                atomic_inc(&ap_poll_requests);
                 ap_dev->queue_count++;
                 if (ap_dev->queue_count == 1)
                         mod_timer(&ap_dev->timeout,
@@ -796,6 +792,27 @@ static void ap_tasklet_fn(unsigned long dummy)
         ap_sm_wait(wait);
 }
 
+static int ap_pending_requests(void)
+{
+        struct ap_device *ap_dev;
+        int id, pending = 0;
+
+        for (id = 0; pending == 0 && id < AP_DEVICES; id++) {
+                spin_lock_bh(&ap_device_list_lock);
+                list_for_each_entry(ap_dev, &ap_device_list, list) {
+                        spin_lock_bh(&ap_dev->lock);
+                        if (ap_dev->queue_count)
+                                pending = 1;
+                        spin_unlock_bh(&ap_dev->lock);
+                        if (pending)
+                                break;
+                }
+                spin_unlock_bh(&ap_device_list_lock);
+        }
+
+        return pending;
+}
+
 /**
  * ap_poll_thread(): Thread that polls for finished requests.
  * @data: Unused pointer
@@ -815,8 +832,7 @@ static int ap_poll_thread(void *data)
         while (!kthread_should_stop()) {
                 add_wait_queue(&ap_poll_wait, &wait);
                 set_current_state(TASK_INTERRUPTIBLE);
-                if (ap_suspend_flag ||
-                    atomic_read(&ap_poll_requests) <= 0) {
+                if (ap_suspend_flag || !ap_pending_requests()) {
                         schedule();
                         try_to_freeze();
                 }
@@ -828,7 +844,8 @@ static int ap_poll_thread(void *data)
                         continue;
                 }
                 ap_tasklet_fn(0);
-        } while (!kthread_should_stop());
+        }
+
         return 0;
 }
 
@@ -1267,9 +1284,6 @@ static int ap_device_remove(struct device *dev)
         spin_unlock_bh(&ap_device_list_lock);
         if (ap_drv->remove)
                 ap_drv->remove(ap_dev);
-        spin_lock_bh(&ap_dev->lock);
-        atomic_sub(ap_dev->queue_count, &ap_poll_requests);
-        spin_unlock_bh(&ap_dev->lock);
         return 0;
 }