From mboxrd@z Thu Jan  1 00:00:00 1970
From: Peter Zijlstra <peterz@infradead.org>
Subject: Re: [PATCH 1/4] s390: convert debug_info.ref_count from atomic_t to
 refcount_t
Date: Mon, 20 Feb 2017 14:39:14 +0100
Message-ID: <20170220133914.GQ6500@twins.programming.kicks-ass.net>
References: <1487588781-15123-1-git-send-email-elena.reshetova@intel.com>
 <1487588781-15123-2-git-send-email-elena.reshetova@intel.com>
 <20170220132424.GA5656@osiris>
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Cc: Elena Reshetova <elena.reshetova@intel.com>,
        linux-kernel@vger.kernel.org, linux-edac@vger.kernel.org,
        x86@kernel.org, sparclinux@vger.kernel.org,
        linux-s390@vger.kernel.org, kvm@vger.kernel.org,
        gregkh@linuxfoundation.org, davem@davemloft.net,
        tglx@linutronix.de, mingo@redhat.com, tony.luck@intel.com,
        hpa@zytor.com, Hans Liljestrand <ishkamiel@gmail.com>,
        Kees Cook <keescook@chromium.org>,
        David Windsor <dwindsor@gmail.com>
To: Heiko Carstens <heiko.carstens@de.ibm.com>
Return-path: <sparclinux-owner@vger.kernel.org>
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On Mon, Feb 20, 2017 at 02:24:24PM +0100, Heiko Carstens wrote:
> On Mon, Feb 20, 2017 at 01:06:18PM +0200, Elena Reshetova wrote:

> > @@ -361,7 +361,7 @@ debug_info_create(const char *name, int pages_per_area, int nr_areas,
> >          debug_area_last = rc;
> >          rc->next = NULL;
> >  
> > -	debug_info_get(rc);
> > +	refcount_set(&rc->ref_count, 1);
> 
> This is not wrong, but I will remove this hunk before applying your patch,
> since this doesn't look like an obvious correct change at first glance.

I suspect; but have not looked at the code; that this would otherwise
attempt to do a 0 -> 1 increment, which refcount_inc() will refuse (and
WARN) over.