From: Linus Torvalds <torvalds@linux-foundation.org>
To: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
Cc: LKML <linux-kernel@vger.kernel.org>,
Andrea Arcangeli <aarcange@redhat.com>,
Hugh Dickins <hughd@google.com>, Christoph Lameter <cl@linux.com>,
Linus Torvalds <torvalds@linux-foundation.org>,
Andrew Morton <akpm@linux-foundation.org>,
Rik van Riel <riel@redhat.com>,
Peter Zijlstra <peterz@infradead.org>,
Andi Kleen <andi@firstfloor.org>, linux-mm <linux-mm@kvack.org>
Subject: Re: [PATCH 3/4] hugetlb, rmap: fix confusing page locking in hugetlb_cow()
Date: Fri, 10 Sep 2010 10:15:46 -0700 (PDT) [thread overview]
Message-ID: <alpine.LFD.2.00.1009101011140.9670@i5.linux-foundation.org> (raw)
In-Reply-To: <1284092586-1179-4-git-send-email-n-horiguchi@ah.jp.nec.com>
On Fri, 10 Sep 2010, Naoya Horiguchi wrote:
>
> - if (!pagecache_page) {
> - page = pte_page(entry);
> + /*
> + * hugetlb_cow() requires page locks of pte_page(entry) and
> + * pagecache_page, so here we need take the former one
> + * when page != pagecache_page or !pagecache_page.
> + */
> + page = pte_page(entry);
> + if (page != pagecache_page)
> lock_page(page);
Why isn't this a potential deadlock? You have two pages, and lock them
both. Is there some ordering guarantee that says that 'pagecache_page' and
'page' will always be in a certain relationship so that you cannot get
A->B and B->A lock ordering?
Please document that ordering rule if so.
Linus
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next prev parent reply other threads:[~2010-09-10 17:15 UTC|newest]
Thread overview: 21+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-09-10 4:23 [PATCH 0/4] hugetlb, rmap: fixes and cleanups Naoya Horiguchi
2010-09-10 4:23 ` [PATCH 1/4] hugetlb, rmap: always use anon_vma root pointer Naoya Horiguchi
2010-09-10 14:37 ` Andrea Arcangeli
2010-09-10 14:40 ` Rik van Riel
2010-09-10 17:19 ` Linus Torvalds
2010-09-10 21:50 ` Andi Kleen
2010-09-10 22:07 ` Linus Torvalds
2010-09-11 2:09 ` Rik van Riel
2010-09-10 4:23 ` [PATCH 2/4] hugetlb, rmap: use hugepage_add_new_anon_rmap() in hugetlb_cow() Naoya Horiguchi
2010-09-10 14:39 ` Andrea Arcangeli
2010-09-10 14:40 ` Rik van Riel
2010-09-10 4:23 ` [PATCH 3/4] hugetlb, rmap: fix confusing page locking " Naoya Horiguchi
2010-09-10 14:41 ` Rik van Riel
2010-09-10 17:15 ` Linus Torvalds [this message]
2010-09-23 23:50 ` Naoya Horiguchi
2010-09-10 4:23 ` [PATCH 4/4] hugetlb, rmap: add BUG_ON(!PageLocked) in hugetlb_add_anon_rmap() Naoya Horiguchi
2010-09-10 14:42 ` Rik van Riel
2010-09-10 14:44 ` Andrea Arcangeli
2010-09-10 9:04 ` [PATCH 0/4] hugetlb, rmap: fixes and cleanups Andi Kleen
2010-09-10 11:47 ` Naoya Horiguchi
2010-09-10 14:30 ` Andi Kleen
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