From: Andrew Morton <akpm@linux-foundation.org>
To: Mike Kravetz <mike.kravetz@oracle.com>
Cc: Baolin Wang <baolin.wang@linux.alibaba.com>,
mgorman@techsingularity.net, osalvador@suse.de, vbabka@suse.cz,
william.lam@bytedance.com, linux-mm@kvack.org,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH 2/2] mm: compaction: fix the possible deadlock when isolating hugetlb pages
Date: Mon, 13 Mar 2023 12:31:02 -0700 [thread overview]
Message-ID: <20230313123102.52118e6007f21c45063fbe79@linux-foundation.org> (raw)
In-Reply-To: <20230313170838.GA3044@monkey>
On Mon, 13 Mar 2023 10:08:38 -0700 Mike Kravetz <mike.kravetz@oracle.com> wrote:
> I suspect holding the lru lock when calling isolate_or_dissolve_huge_page was
> not considered. However, I wonder if this can really happen in practice?
>
> Before the code below, there is this:
>
> /*
> * Periodically drop the lock (if held) regardless of its
> * contention, to give chance to IRQs. Abort completely if
> * a fatal signal is pending.
> */
> if (!(low_pfn % COMPACT_CLUSTER_MAX)) {
> if (locked) {
> unlock_page_lruvec_irqrestore(locked, flags);
> locked = NULL;
> }
> ...
> }
>
> It would seem that the pfn of a hugetlb page would always be a multiple of
> COMPACT_CLUSTER_MAX so we would drop the lock. However, I am not sure if
> that is ALWAYS true and would prefer something like the code you suggested.
>
> Did you actually see this deadlock in practice?
Presumably the lack of lockdep reports about this tells us something?
next prev parent reply other threads:[~2023-03-13 19:31 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-03-13 10:37 [PATCH 1/2] mm: compaction: consider the number of scanning compound pages in isolate fail path Baolin Wang
2023-03-13 10:37 ` [PATCH 2/2] mm: compaction: fix the possible deadlock when isolating hugetlb pages Baolin Wang
2023-03-13 17:08 ` Mike Kravetz
2023-03-13 19:31 ` Andrew Morton [this message]
2023-03-14 4:11 ` Baolin Wang
2023-03-14 17:27 ` Mike Kravetz
2023-03-15 1:27 ` Baolin Wang
2023-03-15 17:17 ` Vlastimil Babka
2023-03-15 15:54 ` [PATCH 1/2] mm: compaction: consider the number of scanning compound pages in isolate fail path Vlastimil Babka
2023-03-16 9:53 ` Baolin Wang
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