[Xen-devel] Re: Regression: patch " hvc_console: display printk messages on console." causing infinite loop with 3.2-rc0 + Xen.

[Rusty Russell <rusty@xxxxxxxxxx>]

On Thu, 27 Oct 2011 01:30:08 -0400, Konrad Rzeszutek Wilk 
<konrad.wilk@xxxxxxxxxx> 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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