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SubjectRe: Regression: patch " hvc_console: display printk messages on console." causing infinite loop with 3.2-rc0 + Xen.
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On Thu, 27 Oct 2011 01:30:08 -0400, Konrad Rzeszutek Wilk <konrad.wilk@oracle.com> wrote:
Non-text part: multipart/mixed
> Hey Miche.
>
> The git commit 361162459f62dc0826b82c9690a741a940f457f0:
>
> hvc_console: display printk messages on console.
>
> is causing an infinite loop when booting Linux under Xen, as so:

lguest too.

This is not a concurrency problem: the issue seems to be that calling
register_console() twice on the same struct console is a bad idea.

Simple fix which works here (might be completely wrong):

diff --git a/drivers/tty/hvc/hvc_console.c b/drivers/tty/hvc/hvc_console.c
--- a/drivers/tty/hvc/hvc_console.c
+++ b/drivers/tty/hvc/hvc_console.c
@@ -197,6 +197,8 @@ static int __init hvc_console_setup(stru
return 0;
}

+static bool console_registered = false;
+
static struct console hvc_console = {
.name = "hvc",
.write = hvc_console_print,
@@ -224,6 +226,7 @@ static struct console hvc_console = {
static int __init hvc_console_init(void)
{
register_console(&hvc_console);
+ console_registered = true;
return 0;
}
console_initcall(hvc_console_init);
@@ -279,8 +282,10 @@ int hvc_instantiate(uint32_t vtermno, in
* now (setup won't fail at this point). It's ok to just
* call register again if previously .setup failed.
*/
- if (index == hvc_console.index)
+ if (index == hvc_console.index && !console_registered) {
register_console(&hvc_console);
+ console_registered = true;
+ }

return 0;
}
@@ -868,7 +873,10 @@ struct hvc_struct *hvc_alloc(uint32_t vt

list_add_tail(&(hp->next), &hvc_structs);
spin_unlock(&hvc_structs_lock);
- register_console(&hvc_console);
+ if (!console_registered) {
+ register_console(&hvc_console);
+ console_registered = true;
+ }

return hp;
}
@@ -880,6 +888,7 @@ int hvc_remove(struct hvc_struct *hp)
struct tty_struct *tty;

unregister_console(&hvc_console);
+ console_registered = false;
spin_lock_irqsave(&hp->lock, flags);
tty = tty_kref_get(hp->tty);


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