Re: [PATCH v3 RESEND 2/2] tpm: add support for nonblocking operation

On Mon, Aug 06, 2018 at 04:05:48PM -0700, James Bottomley wrote:

quoted

@@ -118,25 +155,48 @@ ssize_t tpm_common_write(struct file *file,

const char __user *buf,
 	 * the char dev is held open.
 	 */
 	if (tpm_try_get_ops(priv->chip)) {
-		mutex_unlock(&priv->buffer_mutex);
-		return -EPIPE;
+		ret = -EPIPE;
+		goto out;
 	}
-	out_size = tpm_transmit(priv->chip, priv->space, priv-

quoted

data_buffer,

-				sizeof(priv->data_buffer), 0);
 
-	tpm_put_ops(priv->chip);
-	if (out_size < 0) {
-		mutex_unlock(&priv->buffer_mutex);
-		return out_size;
+	/*
+	 * If in nonblocking mode schedule an async job to send
+	 * the command return the size.
+	 * In case of error the err code will be returned in
+	 * the subsequent read call.
+	 */
+	if (file->f_flags & O_NONBLOCK) {
+		queue_work(tpm_dev_wq, &priv->async_work);
+		return size;

Here you return holding the buffer_mutex, waiting for tpm_async_work to
release it.

Doesn't lockdep complain when locks are left held after returning to
user space? Even if it doesn't, that is a pretty ugly thing to do.

Jason