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virtio: console: wait for first console port for early console output

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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.

[Amit:
  * Use NULL instead of 0 for pointer comparison
  * Rename 'port_added' to 'early_console_added'
  * Re-format, re-word commit message
  * Rebase patch on top of current queue]

Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>
Signed-off-by: Amit Shah <amit.shah@redhat.com>
Acked-by: Chrstian Borntraeger <borntraeger@de.ibm.com>
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
This commit is contained in:
Christian Borntraeger 2011-09-22 23:44:23 +05:30 committed by Rusty Russell
parent 17e5b4f20a
commit 5e38483b35
1 changed files with 20 additions and 0 deletions
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20
drivers/char/virtio_console.c
View file

@ -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/freezer.h>
@ -74,6 +75,7 @@ struct ports_driver_data {
static struct ports_driver_data pdrvdata;
DEFINE_SPINLOCK(pdrvdata_lock);
DECLARE_COMPLETION(early_console_added);
/* This struct holds information that's relevant only for console ports */
struct console {
@ -1366,6 +1368,7 @@ static void handle_control_message(struct ports_device *portdev,
break;
init_port_console(port);
complete(&early_console_added);
/*
* Could remove the port here in case init fails - but
* have to notify the host first.
@ -1668,6 +1671,10 @@ static int __devinit virtcons_probe(struct virtio_device *vdev)
struct ports_device *portdev;
int err;
bool multiport;
bool early = early_put_chars != NULL;
/* Ensure to read early_put_chars now */
barrier();
portdev = kmalloc(sizeof(*portdev), GFP_KERNEL);
if (!portdev) {
@ -1737,6 +1744,19 @@ static int __devinit virtcons_probe(struct virtio_device *vdev)
__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.
*/
if (multiport && early)
wait_for_completion(&early_console_added);
return 0;
free_vqs: