linux-kernel - Re: /proc/*/maps broken on nommu

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Message-ID: <e248c5c8-e55c-46eb-ae8d-f7539cdbeab2@infradead.org>
Date:   Sun, 17 Sep 2023 08:06:51 -0700
From:   Randy Dunlap <rdunlap@...radead.org>
To:     Max Filippov <jcmvbkbc@...il.com>,
        LKML <linux-kernel@...r.kernel.org>,
        Linux Memory Management List <linux-mm@...ck.org>
Cc:     Matthew Wilcox <willy@...radead.org>, Yu Zhao <yuzhao@...gle.com>,
        "Liam R. Howlett" <Liam.Howlett@...cle.com>,
        Vlastimil Babka <vbabka@...e.cz>,
        Davidlohr Bueso <dave@...olabs.net>,
        Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: /proc/*/maps broken on nommu



On 9/17/23 04:38, Max Filippov wrote:
> Hello,
> 
> As of v6.5 cat /proc/*/maps produces empty output on nommu xtensa systems.
> Bisection points to the commit 0c563f148043 ("proc: remove VMA rbtree
> use from nommu").
> It looks like the issue may be not in the m_start (where find_vma(mm,
> addr) returns
> NULL), but in the nommu version of find_vma itself. I've tried replacing nommu
> find_vma implementation with an implementation of the MMU version and it
> fixes the /proc/*/maps output. Kind of (it works as expected on one of
> my systems,
> but consistently locks up on the other).
> 
> Any suggestions of what might be wrong/how to fix it properly?
> 

Hi Max,

There is already a proposed patch and some discussion:

https://lore.kernel.org/lkml/20230915160055.971059-2-ben.wolsieffer@hefring.com/

-- 
~Randy