diff options
Diffstat (limited to 'drivers/char/virtio_console.c')
| -rw-r--r-- | drivers/char/virtio_console.c | 23 |
1 files changed, 19 insertions, 4 deletions
diff --git a/drivers/char/virtio_console.c b/drivers/char/virtio_console.c index 942a9826bd23..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(); @@ -596,6 +599,10 @@ static ssize_t port_fops_write(struct file *filp, const char __user *ubuf, ssize_t ret; bool nonblock; + /* Userspace could be out to fool us */ + if (!count) + return 0; + port = filp->private_data; nonblock = filp->f_flags & O_NONBLOCK; @@ -622,6 +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) @@ -642,7 +657,7 @@ static unsigned int port_fops_poll(struct file *filp, poll_table *wait) poll_wait(filp, &port->waitqueue, wait); ret = 0; - if (port->inbuf) + if (!will_read_block(port)) ret |= POLLIN | POLLRDNORM; if (!will_write_block(port)) ret |= POLLOUT; |