1 files changed, 14 insertions, 3 deletions

diff --git a/drivers/char/virtio_console.c b/drivers/char/virtio_console.c
index c810481a5bc2..0f69c5ec0ecd 100644
--- a/drivers/char/virtio_console.c
+++ b/drivers/char/virtio_console.c
@@ -459,9 +459,12 @@ static ssize_t send_buf(struct port *port, void *in_buf, size_t in_count,
 
         /*
          * Wait till the host acknowledges it pushed out the data we
-         * sent.  This is done for ports in blocking mode or for data
-         * from the hvc_console; the tty operations are performed with
-         * spinlocks held so we can't sleep here.
+         * sent.  This is done for data from the hvc_console; the tty
+         * operations are performed with spinlocks held so we can't
+         * sleep here.  An alternative would be to copy the data to a
+         * buffer and relax the spinning requirement.  The downside is
+         * we need to kmalloc a GFP_ATOMIC buffer each time the
+         * console driver writes something out.
          */
         while (!virtqueue_get_buf(out_vq, &len))
                 cpu_relax();
@@ -626,6 +629,14 @@ static ssize_t port_fops_write(struct file *filp, const char __user *ubuf,
                 goto free_buf;
         }
 
+        /*
+         * We now ask send_buf() to not spin for generic ports -- we
+         * can re-use the same code path that non-blocking file
+         * descriptors take for blocking file descriptors since the
+         * wait is already done and we're certain the write will go
+         * through to the host.
+         */
+        nonblock = true;
         ret = send_buf(port, buf, count, nonblock);
 
         if (nonblock && ret > 0)