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Message-ID: <1416291158.2327.11.camel@TP420>
Subject: Re: [powerpc] init nvram_pstore_info's buf_lock
From: Li Zhong <zhong@linux.vnet.ibm.com>
To: Michael Ellerman <mpe@ellerman.id.au>
Date: Tue, 18 Nov 2014 14:12:38 +0800
In-Reply-To: <20141118043314.4517C14011D@ozlabs.org>
References: <20141118043314.4517C14011D@ozlabs.org>
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On 二, 2014-11-18 at 15:33 +1100, Michael Ellerman wrote:
> On Mon, 2014-17-11 at 02:52:30 UTC, Li Zhong wrote:
> > It seems nvram_pstore_info's buf_lock is not initialized before
> > registering, which causes some strange behavior when trying to obtain
> > the lock during kdump process.
> 
> What kind of strange behaviour? Does it still work and just print a warning?
> 
> It's static, so I'd expect it to be unlocked by default.

Yes, you are right. It still works. 

I saw it on a UP configuration, noticed the console stopped for a couple
of seconds, then "lockup suspected" warning printed out, but then it
continued to run. 

After some further checking, it seems working as designed for the UP
spinlock debug, from the comments in spinlock_up.h

 * In the debug case, 1 means unlocked, 0 means locked. (the values
 * are inverted, to catch initialization bugs)

So try lock fails, and lockup reported, but then arch_spin_lock()
passes. 

Thanks, Zhong

> 
> cheers
>