[PATCH 5/8] char: xillybus: Refactor flush function

[Eli Billauer]

Previous flush_downstream() looped on wait_event_interruptible() and
wait_event_interruptible_timeout() without returning if an interrupt
occurred. Replace these with non-interruptible counterparts and use
wake_up() instead of wake_up_interruptible() on the relevant wait queue.

In addition, flush_downstream()'s @interruptible argument is removed.
Instead, this function either waits with a timeout only, or with an
interruptible wait. This is what the callers of this function requested
anyhow.

Assisted-by: Sashiko-0.2.5:gemini-3.1-pro-preview
Link: https://sashiko.dev/#/patchset/20260724094302.50761-1-eli.billauer@xxxxxxxxx
Signed-off-by: Eli Billauer <eli.billauer@xxxxxxxxx>
---
 drivers/char/xillybus/xillyusb.c | 89 +++++++++++++++-----------------
 1 file changed, 41 insertions(+), 48 deletions(-)

diff --git a/drivers/char/xillybus/xillyusb.c b/drivers/char/xillybus/xillyusb.c
index 73e26f254693..3afd9bd38a1a 100644
--- a/drivers/char/xillybus/xillyusb.c
+++ b/drivers/char/xillybus/xillyusb.c
@@ -604,7 +604,7 @@ static void wakeup_all(struct work_struct *work)
 
 		mutex_unlock(&chan->lock);
 
-		wake_up_interruptible(&chan->flushq);
+		wake_up(&chan->flushq);
 	}
 
 	mutex_unlock(&xdev->process_in_mutex);
@@ -923,12 +923,12 @@ static int process_in_opcode(struct xillyusb_dev *xdev,
 
 	case OPCODE_REACHED_CHECKPOINT:
 		chan->flushing = 0;
-		wake_up_interruptible(&chan->flushq);
+		wake_up(&chan->flushq);
 		break;
 
 	case OPCODE_CANCELED_CHECKPOINT:
 		chan->canceled = 1;
-		wake_up_interruptible(&chan->flushq);
+		wake_up(&chan->flushq);
 		break;
 
 	default:
@@ -1130,11 +1130,13 @@ static int xillyusb_send_opcode(struct xillyusb_dev *xdev,
  * chan->flushed is there to avoid multiple flushes at the same position,
  * in particular as a result of programs that close the file descriptor
  * e.g. after a dup2() for redirection.
+ *
+ * If timeout == 0, no timeout is applied and the wait is interruptible,
+ * otherwise a timeout is applied but the wait is non-interruptible.
  */
 
 static int flush_downstream(struct xillyusb_channel *chan,
-			    unsigned long timeout,
-			    bool interruptible)
+			    unsigned long timeout)
 {
 	struct xillyusb_dev *xdev = chan->xdev;
 	int chan_num = chan->chan_idx << 1;
@@ -1159,21 +1161,22 @@ static int flush_downstream(struct xillyusb_channel *chan,
 			return rc; /* Only real error, never -EINTR */
 
 		/* Ignoring interrupts. Cancellation must be handled */
-		while (!chan->canceled) {
-			left_to_sleep = cancel_deadline - jiffies;
+		left_to_sleep = cancel_deadline - jiffies;
 
-			if (left_to_sleep <= 0) {
-				report_io_error(xdev, -EIO);
-				return -EIO;
-			}
+		rc = 0;
 
-			rc = wait_event_interruptible_timeout(chan->flushq,
-							      chan->canceled ||
-							      xdev->error,
-							      left_to_sleep);
+		if (left_to_sleep > 0)
+			rc = wait_event_timeout(chan->flushq,
+						chan->canceled ||
+						xdev->error,
+						left_to_sleep);
+
+		if (xdev->error)
+			return xdev->error;
 
-			if (xdev->error)
-				return xdev->error;
+		if (!rc) {
+			report_io_error(xdev, -EIO);
+			return -EIO;
 		}
 	}
 
@@ -1194,40 +1197,30 @@ static int flush_downstream(struct xillyusb_channel *chan,
 	if (rc)
 		return rc; /* Only real error, never -EINTR */
 
-	if (!timeout) {
-		while (chan->flushing) {
-			rc = wait_event_interruptible(chan->flushq,
-						      !chan->flushing ||
-						      xdev->error);
-			if (xdev->error)
-				return xdev->error;
-
-			if (interruptible && rc)
-				return -EINTR;
-		}
+	if (timeout) {
+		left_to_sleep = deadline - jiffies;
 
-		goto done;
-	}
+		rc = 0;
 
-	while (chan->flushing) {
-		left_to_sleep = deadline - jiffies;
+		if (left_to_sleep > 0)
+			rc = wait_event_timeout(chan->flushq,
+						!chan->flushing ||
+						xdev->error,
+						left_to_sleep);
 
-		if (left_to_sleep <= 0)
+		if (!rc)
 			return -ETIMEDOUT;
+	} else {
+		rc = wait_event_interruptible(chan->flushq,
+					      !chan->flushing || xdev->error);
+	}
 
-		rc = wait_event_interruptible_timeout(chan->flushq,
-						      !chan->flushing ||
-						      xdev->error,
-						      left_to_sleep);
-
-		if (xdev->error)
-			return xdev->error;
+	if (xdev->error)
+		return xdev->error;
 
-		if (interruptible && rc < 0)
-			return -EINTR;
-	}
+	if (rc < 0)
+		return -EINTR;
 
-done:
 	chan->flushed = 1;
 	return 0;
 }
@@ -1335,7 +1328,7 @@ static int xillyusb_open(struct inode *inode, struct file *filp)
 		 * This can't go wrong unless there's a serious hardware error
 		 * (or the computer is stuck for 500 ms?)
 		 */
-		rc = flush_downstream(chan, XILLY_RESPONSE_TIMEOUT, false);
+		rc = flush_downstream(chan, XILLY_RESPONSE_TIMEOUT);
 
 		if (rc == -ETIMEDOUT) {
 			rc = -EIO;
@@ -1629,7 +1622,7 @@ static int xillyusb_flush(struct file *filp, fl_owner_t id)
 	 * the user pressed CTRL-C, that interrupt will still be in flight by
 	 * the time we reach here, and the opportunity to flush is lost.
 	 */
-	rc = flush_downstream(chan, HZ, false);
+	rc = flush_downstream(chan, HZ);
 
 	mutex_unlock(&chan->out_mutex);
 
@@ -1699,7 +1692,7 @@ static ssize_t xillyusb_write(struct file *filp, const char __user *userbuf,
 	}
 
 	if (chan->out_synchronous) {
-		int flush_rc = flush_downstream(chan, 0, true);
+		int flush_rc = flush_downstream(chan, 0);
 
 		if (flush_rc && !rc)
 			rc = flush_rc;
@@ -1836,7 +1829,7 @@ static loff_t xillyusb_llseek(struct file *filp, loff_t offset, int whence)
 
 	if (chan->writable) {
 		chan->flushed = 0;
-		rc = flush_downstream(chan, HZ, false);
+		rc = flush_downstream(chan, HZ);
 	}
 
 end:
-- 
2.17.1