linux-kernel - Re: [PATCH 3/3] s390/mm: fix mis-accounting of pgtable

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Message-ID: <20181031103623.6ykzsjdenrpeth7x@kshutemo-mobl1>
Date:   Wed, 31 Oct 2018 13:36:23 +0300
From:   "Kirill A. Shutemov" <kirill@...temov.name>
To:     Heiko Carstens <heiko.carstens@...ibm.com>
Cc:     "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
        Li Wang <liwang@...hat.com>,
        Guenter Roeck <linux@...ck-us.net>,
        Janosch Frank <frankja@...ux.vnet.ibm.com>,
        linux-kernel <linux-kernel@...r.kernel.org>,
        Linux-MM <linux-mm@...ck.org>,
        Martin Schwidefsky <schwidefsky@...ibm.com>
Subject: Re: [PATCH 3/3] s390/mm: fix mis-accounting of pgtable_bytes

On Wed, Oct 31, 2018 at 11:09:44AM +0100, Heiko Carstens wrote:
> On Wed, Oct 31, 2018 at 07:31:49AM +0100, Martin Schwidefsky wrote:
> > Thanks for testing. Unfortunately Heiko reported another issue yesterday
> > with the patch applied. This time the other way around:
> > 
> > BUG: non-zero pgtables_bytes on freeing mm: -16384
> > 
> > I am trying to understand how this can happen. For now I would like to
> > keep the patch on hold in case they need another change.
> 
> FWIW, Kirill: is there a reason why this "BUG:" output is done with
> pr_alert() and not with VM_BUG_ON() or one of the WARN*() variants?
> 
> That would to get more information with DEBUG_VM and / or
> panic_on_warn=1 set. At least for automated testing it would be nice
> to have such triggers.

Stack trace is not helpful there. It will always show the exit path which
is useless.

-- 
 Kirill A. Shutemov