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SubjectRe: [PATCH 4/7] hvc_console: Fix race between hvc_close and hvc_remove
Amit Shah wrote:
> On (Fri) Mar 26 2010 [14:43:56], Sachin Sant wrote:
>>> And this suggests that hvc_kick() is called before hvc_task is
>>> initialised, ie, before hvc_init() is called.
>>> Does this help?
>> Hi Amit,
>> I too ran into this issue as reported by Anton. Unfortunately in my
>> case the following suggested patch does not help boot the powerpc
>> box successfully. The boot still hangs with following messages
> Was the hang you saw before applying this patch at the same place / for
> the same reason?
Yes the machine hangs at the same place with or without the patch.

>> mount: can't find /root/proc in /etc/fstab or /etc/mtab
>> /sbin/smart_agetty: can not determine 'console' speed
> OK, this gets even murkier. I don't know why taking a few krefs modifies
> hvc_console behaviour to such an extent.
Looking at the commit e74d098c66543d0731de62eb747ccd5b636a6f4c,
i see that for every tty_kref_get() there is a corresponding
tty_kref_put() except maybe for the one in the following patch snippet

spin_lock_irqsave(&hp->lock, flags);
/* Check and then increment for fast path open. */
if (hp->count++ > 0) {
+ tty_kref_get(tty);
spin_unlock_irqrestore(&hp->lock, flags);
return 0;

I don't know this code very well but we might be missing a
corresponding tty_kref_put() some place ?

If i comment out the above tty_kref_get() call, the machine
boots fine with or without the suggested patch.


>> Just to confirm i too am facing same issue as reported by Anton,
>> reverted commit e74d098c66543d0731de62eb747ccd5b636a6f4c and that allowed
>> by box to boot successfully.
> Which module uses hvc_console in your case?
> Amit


Sachin Sant
IBM Linux Technology Center
India Systems and Technology Labs
Bangalore, India

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