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Date:   Mon, 20 Apr 2020 09:34:34 +0200
From:   Michal Hocko <mhocko@kernel.org>
To:     Andrew Morton <akpm@linux-foundation.org>
Cc:     David Hildenbrand <david@redhat.com>, linux-kernel@vger.kernel.org,
        linux-mm@kvack.org, Pavel Tatashin <pasha.tatashin@soleen.com>,
        Pankaj Gupta <pankaj.gupta.linux@gmail.com>,
        Baoquan He <bhe@redhat.com>,
        Shile Zhang <shile.zhang@linux.alibaba.com>,
        Kirill Tkhai <ktkhai@virtuozzo.com>,
        Daniel Jordan <daniel.m.jordan@oracle.com>,
        Alexander Duyck <alexander.duyck@gmail.com>,
        Oscar Salvador <osalvador@suse.de>
Subject: Re: [PATCH v2] mm/page_alloc: fix watchdog soft lockups during
 set_zone_contiguous()
Message-ID: <20200420073434.GE27314@dhcp22.suse.cz>
References: <20200416073417.5003-1-david@redhat.com>
 <20200417151247.0068d5aa3f026ced2289ce31@linux-foundation.org>
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On Fri 17-04-20 15:12:47, Andrew Morton wrote:
> On Thu, 16 Apr 2020 09:34:17 +0200 David Hildenbrand <david@redhat.com> wrote:
> 
> > Without CONFIG_PREEMPT, it can happen that we get soft lockups detected,
> > e.g., while booting up.
> > 
> > ...
> > 
> > --- a/mm/page_alloc.c
> > +++ b/mm/page_alloc.c
> > @@ -1607,6 +1607,7 @@ void set_zone_contiguous(struct zone *zone)
> >  		if (!__pageblock_pfn_to_page(block_start_pfn,
> >  					     block_end_pfn, zone))
> >  			return;
> > +		cond_resched();
> >  	}
> >  
> >  	/* We confirm that there is no hole */
> 
> I added cc:stable to this one.  Please let me know if that wasn't a
> good idea.

Really large memory setups tend to run on distribution kernels so
backporting to old kernels doesn't really harm.
-- 
Michal Hocko
SUSE Labs