linux-kernel - Re: mm: swap: locking in release

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Message-ID: <404b3d6e-510e-c15f-a28b-7425bcc67cc2@nokia.com>
Date:   Tue, 5 Apr 2022 16:00:54 +0200
From:   Alexander Sverdlin <alexander.sverdlin@...ia.com>
To:     Michal Hocko <mhocko@...e.com>
Cc:     Nicholas Piggin <npiggin@...il.com>,
        Alexander Duyck <alexanderduyck@...com>,
        Matthew Wilcox <willy@...radead.org>,
        Hugh Dickins <hughd@...gle.com>, Yu Zhao <yuzhao@...gle.com>,
        Mel Gorman <mgorman@...hsingularity.net>,
        Lee Schermerhorn <lee.schermerhorn@...com>,
        Sasha Levin <sashal@...nel.org>,
        Andrew Morton <akpm@...ux-foundation.org>, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org
Subject: Re: mm: swap: locking in release_pages()

Hello Michal!

On 05/04/2022 13:45, Michal Hocko wrote:
>>>> 1. Crash of v5.4.170 on an ARM32 machine:
>>>>
>>>> Unable to handle kernel NULL pointer dereference at virtual address 00000104
>>>> pgd = e138149d
>>>> [00000104] *pgd=84d2fd003, *pmd=8ffd6f003
>>>> Internal error: Oops: a07 [#1] PREEMPT SMP ARM
>>>> ...
>>>> CPU: 1 PID: 6172 Comm: AaSysInfoRColle Tainted: G    B      O      5.4.170-... #1
>>>> Hardware name: Keystone
>>>> PC is at release_pages+0x194/0x358
>>>> LR is at release_pages+0x10c/0x358
>>> Which LOC does this correspond to? (faddr2line should give you a nice
>>> output).
>> Sorry, I forgot this info in the initial report:
>>
>> this is indeed the del_page_from_lru_list() in this crash.
> Could you be more specific please? Is the problem in list_del or
> update_lru_size?

static inline void __list_del(struct list_head * prev, struct list_head * next)
{
        next->prev = prev;    <--

-- 
Best regards,
Alexander Sverdlin.