Hi Christian,
On (Wed) 21 Sep 2011 [17:52:23], Christian Borntraeger wrote:
> Amit,
>
> can you have a look at the patch below and give feedback or apply
> if appropriate?
The patch looks good. Just a couple of comments:
> On s390 I have seen some random "Warning: unable to open an initial
> console" boot failure. Turns out that tty_open fails, because the
> hvc_alloc was not yet done. In former times this could not happen,
> since the probe function automatically called hvc_alloc. With newer
> versions (multiport) some host<->guest interaction is required
> before hvc_alloc is called. This might be too late, especially if
> an initramfs is involved. Lets use a completion if we have
> multiport and an early console.
>
> Signed-off-by: Christian Borntraeger <borntraeger@xxxxxxxxxx>
>
> ---
> drivers/char/virtio_console.c | 18 ++++++++++++++++++
> 1 file changed, 18 insertions(+)
>
> Index: b/drivers/char/virtio_console.c
> ===================================================================
> --- a/drivers/char/virtio_console.c
> +++ b/drivers/char/virtio_console.c
> @@ -19,6 +19,7 @@
> */
> #include <linux/cdev.h>
> #include <linux/debugfs.h>
> +#include <linux/completion.h>
> #include <linux/device.h>
> #include <linux/err.h>
> #include <linux/fs.h>
> @@ -73,6 +74,7 @@ struct ports_driver_data {
> static struct ports_driver_data pdrvdata;
>
> DEFINE_SPINLOCK(pdrvdata_lock);
> +DECLARE_COMPLETION(port_added);
>
> /* This struct holds information that's relevant only for console ports */
> struct console {
> @@ -1352,6 +1354,7 @@ static void handle_control_message(struc
> break;
>
> init_port_console(port);
> + complete(&port_added);
> /*
> * Could remove the port here in case init fails - but
> * have to notify the host first.
> @@ -1648,6 +1651,10 @@ static int __devinit virtcons_probe(stru
> struct ports_device *portdev;
> int err;
> bool multiport;
> + bool early = early_put_chars != 0;
Check for NULL instead of 0. Is it necessary to create this variable
instead of checking for early_put_chars != NULL below?
> +
> + /* Ensure to read early_put_chars now */
> + barrier();
>
> portdev = kmalloc(sizeof(*portdev), GFP_KERNEL);
> if (!portdev) {
> @@ -1719,6 +1726,17 @@ static int __devinit virtcons_probe(stru
>
> __send_control_msg(portdev, VIRTIO_CONSOLE_BAD_ID,
> VIRTIO_CONSOLE_DEVICE_READY, 1);
> +
> + /* If there was an early virtio console, assume that there are no
> + * other consoles. We need to wait until the hvc_alloc matches the
> + * hvc_instantiate, otherwise tty_open will complain, resulting in
> + * a "Warning: unable to open an initial console" boot failure.
> + * Without multiport this is done in add_port above. With multiport
> + * this might take some host<->guest communication - thus we have to
> + * wait. */
This file uses comments in the form
/*
* ...
*/
> + if (multiport && early)
> + wait_for_completion(&port_added);
> +
Can there be a problem to not timeout this wait? Maybe it's not a
real problem; just thinking out aloud.
Amit
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