linux-kernel - Re: [PATCH] mm/page_alloc: Add a reason for reserved pages in has_unmovable

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Message-ID: <1570195839.5576.273.camel@lca.pw>
Date:   Fri, 04 Oct 2019 09:30:39 -0400
From:   Qian Cai <cai@....pw>
To:     Michal Hocko <mhocko@...nel.org>
Cc:     Anshuman Khandual <anshuman.khandual@....com>, linux-mm@...ck.org,
        Andrew Morton <akpm@...ux-foundation.org>,
        Vlastimil Babka <vbabka@...e.cz>,
        Oscar Salvador <osalvador@...e.de>,
        Mel Gorman <mgorman@...hsingularity.net>,
        Mike Rapoport <rppt@...ux.ibm.com>,
        Dan Williams <dan.j.williams@...el.com>,
        Pavel Tatashin <pavel.tatashin@...rosoft.com>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] mm/page_alloc: Add a reason for reserved pages in
 has_unmovable_pages()

On Fri, 2019-10-04 at 15:07 +0200, Michal Hocko wrote:
> On Fri 04-10-19 08:56:16, Qian Cai wrote:
> [...]
> > It might be a good time to rethink if it is really a good idea to dump_page()
> > at all inside has_unmovable_pages(). As it is right now, it is a a potential
> > deadlock between console vs memory offline. More details are in this thread,
> > 
> > https://lore.kernel.org/lkml/1568817579.5576.172.camel@lca.pw/
> 
> Huh. That would imply we cannot do any printk from that path, no?

Yes, or use something like printk_deferred() or it needs to rework of the
current console locking which I have no clue yet.