GenWQE: Support blocking when DDCB queue is busy
When the GenWQE hardware queue was busy, the driver returned simply
-EBUSY. This caused polling by applications which increased the load
on the already busy system. This change implements the possiblity to
sleep on a waitqueue instead when the DDCB queue is busy. The
requestor is woken up when there is free space on the queue again.
The old way to get -EBUSY is still available if the device is openend
with O_NONBLOCKING. The default is now blocking behavior.
Signed-off-by: Frank Haverkamp <haver@linux.vnet.ibm.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
diff --git a/drivers/misc/genwqe/card_ddcb.c b/drivers/misc/genwqe/card_ddcb.c
index 51480e4..6d51e5f 100644
--- a/drivers/misc/genwqe/card_ddcb.c
+++ b/drivers/misc/genwqe/card_ddcb.c
@@ -448,8 +448,10 @@
queue->ddcbs_completed++;
queue->ddcbs_in_flight--;
- /* wake up process waiting for this DDCB */
+ /* wake up process waiting for this DDCB, and
+ processes on the busy queue */
wake_up_interruptible(&queue->ddcb_waitqs[queue->ddcb_act]);
+ wake_up_interruptible(&queue->busy_waitq);
pick_next_one:
queue->ddcb_act = (queue->ddcb_act + 1) % queue->ddcb_max;
@@ -745,14 +747,16 @@
/**
* __genwqe_enqueue_ddcb() - Enqueue a DDCB
- * @cd: pointer to genwqe device descriptor
- * @req: pointer to DDCB execution request
+ * @cd: pointer to genwqe device descriptor
+ * @req: pointer to DDCB execution request
+ * @f_flags: file mode: blocking, non-blocking
*
* Return: 0 if enqueuing succeeded
* -EIO if card is unusable/PCIe problems
* -EBUSY if enqueuing failed
*/
-int __genwqe_enqueue_ddcb(struct genwqe_dev *cd, struct ddcb_requ *req)
+int __genwqe_enqueue_ddcb(struct genwqe_dev *cd, struct ddcb_requ *req,
+ unsigned int f_flags)
{
struct ddcb *pddcb;
unsigned long flags;
@@ -760,6 +764,7 @@
struct pci_dev *pci_dev = cd->pci_dev;
u16 icrc;
+ retry:
if (cd->card_state != GENWQE_CARD_USED) {
printk_ratelimited(KERN_ERR
"%s %s: [%s] Card is unusable/PCIe problem Req#%d\n",
@@ -785,9 +790,24 @@
pddcb = get_next_ddcb(cd, queue, &req->num); /* get ptr and num */
if (pddcb == NULL) {
+ int rc;
+
spin_unlock_irqrestore(&queue->ddcb_lock, flags);
- queue->busy++;
- return -EBUSY;
+
+ if (f_flags & O_NONBLOCK) {
+ queue->return_on_busy++;
+ return -EBUSY;
+ }
+
+ queue->wait_on_busy++;
+ rc = wait_event_interruptible(queue->busy_waitq,
+ queue_free_ddcbs(queue) != 0);
+ dev_dbg(&pci_dev->dev, "[%s] waiting for free DDCB: rc=%d\n",
+ __func__, rc);
+ if (rc == -ERESTARTSYS)
+ return rc; /* interrupted by a signal */
+
+ goto retry;
}
if (queue->ddcb_req[req->num] != NULL) {
@@ -890,9 +910,11 @@
* __genwqe_execute_raw_ddcb() - Setup and execute DDCB
* @cd: pointer to genwqe device descriptor
* @req: user provided DDCB request
+ * @f_flags: file mode: blocking, non-blocking
*/
int __genwqe_execute_raw_ddcb(struct genwqe_dev *cd,
- struct genwqe_ddcb_cmd *cmd)
+ struct genwqe_ddcb_cmd *cmd,
+ unsigned int f_flags)
{
int rc = 0;
struct pci_dev *pci_dev = cd->pci_dev;
@@ -908,7 +930,7 @@
__func__, cmd->asiv_length);
return -EINVAL;
}
- rc = __genwqe_enqueue_ddcb(cd, req);
+ rc = __genwqe_enqueue_ddcb(cd, req, f_flags);
if (rc != 0)
return rc;
@@ -1014,7 +1036,8 @@
queue->ddcbs_in_flight = 0; /* statistics */
queue->ddcbs_max_in_flight = 0;
queue->ddcbs_completed = 0;
- queue->busy = 0;
+ queue->return_on_busy = 0;
+ queue->wait_on_busy = 0;
queue->ddcb_seq = 0x100; /* start sequence number */
queue->ddcb_max = genwqe_ddcb_max; /* module parameter */
@@ -1054,7 +1077,7 @@
queue->ddcb_next = 0; /* queue is empty */
spin_lock_init(&queue->ddcb_lock);
- init_waitqueue_head(&queue->ddcb_waitq);
+ init_waitqueue_head(&queue->busy_waitq);
val64 = ((u64)(queue->ddcb_max - 1) << 8); /* lastptr */
__genwqe_writeq(cd, queue->IO_QUEUE_CONFIG, 0x07); /* iCRC/vCRC */
@@ -1302,6 +1325,7 @@
for (i = 0; i < queue->ddcb_max; i++)
wake_up_interruptible(&queue->ddcb_waitqs[queue->ddcb_act]);
+ wake_up_interruptible(&queue->busy_waitq);
spin_unlock_irqrestore(&queue->ddcb_lock, flags);
return 0;