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From:   Muchun Song <songmuchun@bytedance.com>
Date:   Fri, 4 Mar 2022 20:16:46 +0800
Message-ID: <CAMZfGtUUG3KqMLWs32vL7fwUAVhgJuiE4OvW_B0K1zeR8oacVw@mail.gmail.com>
Subject: Re: [PATCH 04/16] mm/migration: reduce the rcu lock duration
To:     Miaohe Lin <linmiaohe@huawei.com>
Cc:     Andrew Morton <akpm@linux-foundation.org>,
        Mike Kravetz <mike.kravetz@oracle.com>,
        Yang Shi <shy828301@gmail.com>,
        Matthew Wilcox <willy@infradead.org>,
        Huang Ying <ying.huang@intel.com>, Zi Yan <ziy@nvidia.com>,
        Minchan Kim <minchan@kernel.org>,
        Alistair Popple <apopple@nvidia.com>,
        ave.hansen@linux.intel.com, o451686892@gmail.com,
        Mina Almasry <almasrymina@google.com>,
        John Hubbard <jhubbard@nvidia.com>,
        Ralph Campbell <rcampbell@nvidia.com>,
        Peter Xu <peterx@redhat.com>,
        =?UTF-8?B?SE9SSUdVQ0hJIE5BT1lBKOWggOWPoyDnm7TkuZ8p?= 
        <naoya.horiguchi@nec.com>, Michal Hocko <mhocko@suse.com>,
        riel@redhat.com, Linux Memory Management List <linux-mm@kvack.org>,
        LKML <linux-kernel@vger.kernel.org>
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On Fri, Mar 4, 2022 at 5:35 PM Miaohe Lin <linmiaohe@huawei.com> 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.
>
> Signed-off-by: Miaohe Lin <linmiaohe@huawei.com>

Also simple.

Reviewed-by: Muchun Song <songmuchun@bytedance.com>