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Date:   Mon, 22 Mar 2021 15:35:25 +0100
From:   Michal Hocko <mhocko@suse.com>
To:     Mike Kravetz <mike.kravetz@oracle.com>
Cc:     linux-mm@kvack.org, linux-kernel@vger.kernel.org,
        Shakeel Butt <shakeelb@google.com>,
        Oscar Salvador <osalvador@suse.de>,
        David Hildenbrand <david@redhat.com>,
        Muchun Song <songmuchun@bytedance.com>,
        David Rientjes <rientjes@google.com>,
        Miaohe Lin <linmiaohe@huawei.com>,
        Peter Zijlstra <peterz@infradead.org>,
        Matthew Wilcox <willy@infradead.org>,
        HORIGUCHI NAOYA <naoya.horiguchi@nec.com>,
        "Aneesh Kumar K . V" <aneesh.kumar@linux.ibm.com>,
        Waiman Long <longman@redhat.com>, Peter Xu <peterx@redhat.com>,
        Mina Almasry <almasrymina@google.com>,
        Andrew Morton <akpm@linux-foundation.org>
Subject: Re: [RFC PATCH 6/8] hugetlb: make free_huge_page irq safe
Message-ID: <YFirLYVAQBjA8TVi@dhcp22.suse.cz>
References: <20210319224209.150047-1-mike.kravetz@oracle.com>
 <20210319224209.150047-7-mike.kravetz@oracle.com>
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On Fri 19-03-21 15:42:07, Mike Kravetz wrote:
> Commit c77c0a8ac4c5 ("mm/hugetlb: defer freeing of huge pages if in
> non-task context") was added to address the issue of free_huge_page
> being called from irq context.  That commit hands off free_huge_page
> processing to a workqueue if !in_task.  However, as seen in [1] this
> does not cover all cases.  Instead, make the locks taken in the
> free_huge_page irq safe.
> 
> This patch does the following:
> - Make hugetlb_lock irq safe.  This is mostly a simple process of
>   changing spin_*lock calls to spin_*lock_irq* calls.
> - Make subpool lock irq safe in a similar manner.
> - Revert the !in_task check and workqueue handoff.

This is not sufficient (and 0day bot has captured that already). You
cannot call update_and_free_page from the same context.

-- 
Michal Hocko
SUSE Labs