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

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Message-Id: <615D1FE9-C16A-4FD5-A113-1C50AB3F0222@lca.pw>
Date:   Sat, 5 Oct 2019 18:38:38 -0400
From:   Qian Cai <cai@....pw>
To:     Andrew Morton <akpm@...ux-foundation.org>
Cc:     Michal Hocko <mhocko@...nel.org>,
        Anshuman Khandual <Anshuman.Khandual@....com>,
        linux-mm@...ck.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 Oct 5, 2019, at 5:22 PM, Andrew Morton <akpm@...ux-foundation.org> wrote:
> 
> Apparently some console drivers can do memory allocation on the printk()
> path.
> 
> This behavior is daft, IMO.  Have we identified which ones and looked
> into fixing them?

Not necessary that simple. It is more of 2+ CPUs required to trigger the deadlock. Please see my v2 patch I sent which has all the information. Especially, the thread link included there which contains a few lockdep splat traces and the s390 one in the patch description.