From: Sachin Sant <sachinp@in•ibm.com>
To: Amit Shah <amit.shah@redhat•com>
Cc: Greg Kroah-Hartman <gregkh@suse•de>,
a.p.zijlstra@chello•nl, Rusty Russell <rusty@rustcorp•com.au>,
linux-kernel@vger•kernel.org, linuxppc-dev@ozlabs•org,
Anton Blanchard <anton@samba•org>,
tglx@linutronix•de,
Linus Torvalds <torvalds@linux-foundation•org>,
mingo@elte•hu, Alan Cox <alan@lxorguk•ukuu.org.uk>
Subject: Re: [PATCH 4/7] hvc_console: Fix race between hvc_close and hvc_remove
Date: Fri, 26 Mar 2010 17:12:22 +0530 [thread overview]
Message-ID: <4BAC9D9E.5070901@in.ibm.com> (raw)
In-Reply-To: <20100326095821.GA7039@amit-x200.redhat.com>
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);
hvc_kick();
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.
Thanks
-Sachin
>
>> 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
---------------------------------
next prev parent reply other threads:[~2010-03-26 11:42 UTC|newest]
Thread overview: 22+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <20100319151326.GC8541@kroah.com>
2010-03-19 15:18 ` [PATCH 4/7] hvc_console: Fix race between hvc_close and hvc_remove Greg Kroah-Hartman
2010-03-20 21:04 ` Benjamin Herrenschmidt
2010-03-21 4:37 ` Amit Shah
2010-03-24 12:19 ` Amit Shah
2010-03-25 23:30 ` Anton Blanchard
2010-03-26 2:01 ` Amit Shah
2010-03-26 9:13 ` Sachin Sant
2010-03-26 9:58 ` Amit Shah
2010-03-26 10:54 ` Stephen Rothwell
2010-03-26 11:42 ` Sachin Sant [this message]
2010-03-26 11:52 ` Alan Cox
2010-03-26 12:49 ` Amit Shah
2010-03-26 12:43 ` Amit Shah
2010-04-06 11:42 ` Anton Blanchard
2010-04-06 12:09 ` Amit Shah
2010-04-06 12:27 ` Sachin Sant
2010-04-06 12:32 ` Alan Cox
2010-04-08 0:26 ` Rusty Russell
2010-03-24 10:45 ` Benjamin Herrenschmidt
2010-03-24 10:57 ` Amit Shah
2010-03-24 11:37 ` Alan Cox
2010-03-24 15:05 ` Amit Shah
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