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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>
hifive-unleashed-5.1
Martin Schwidefsky 2016-09-21 14:12:53 +02:00
parent 0db78559f9
commit 9af3e04ee4
1 changed files with 24 additions and 10 deletions
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34
drivers/s390/crypto/ap_bus.c
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@ -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;
}