linux-kernel - Re: [PATCH 1/4] mm/migration: reduce the rcu lock duration

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Message-ID: <YlQ2n2wrhqpgF3Ow@infradead.org>
Date:   Mon, 11 Apr 2022 07:09:35 -0700
From:   Christoph Hellwig <hch@...radead.org>
To:     Miaohe Lin <linmiaohe@...wei.com>
Cc:     akpm@...ux-foundation.org, mike.kravetz@...cle.com,
        shy828301@...il.com, willy@...radead.org, ying.huang@...el.com,
        ziy@...dia.com, minchan@...nel.org, apopple@...dia.com,
        dave.hansen@...ux.intel.com, o451686892@...il.com,
        jhubbard@...dia.com, peterx@...hat.com, naoya.horiguchi@....com,
        mhocko@...e.com, riel@...hat.com, osalvador@...e.de,
        david@...hat.com, sfr@...b.auug.org.au, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/4] mm/migration: reduce the rcu lock duration

On Sat, Apr 09, 2022 at 03:38:43PM +0800, Miaohe Lin wrote:
> rcu_read_lock is required by grabbing the task refcount but it's not
> needed for ptrace_may_access. So we could release the rcu lock after
> task refcount is successfully grabbed to reduce the rcu holding time.
> 
> Reviewed-by: Muchun Song <songmuchun@...edance.com>
> Signed-off-by: Miaohe Lin <linmiaohe@...wei.com>

Looks good:

Reviewed-by: Christoph Hellwig <hch@....de>