From: Matthew Wilcox <willy@infradead.org>
To: Miaohe Lin <linmiaohe@huawei.com>
Cc: akpm@linux-foundation.org, naoya.horiguchi@nec.com,
peterx@redhat.com, apopple@nvidia.com, ying.huang@intel.com,
osalvador@suse.de, mike.kravetz@oracle.com,
songmuchun@bytedance.com, hch@lst.de, dhowells@redhat.com,
cl@linux.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH v4 1/4] mm: reduce the rcu lock duration
Date: Tue, 31 May 2022 13:58:31 +0100 [thread overview]
Message-ID: <YpYQ937N8Daad6u/@casper.infradead.org> (raw)
In-Reply-To: <20220530113016.16663-2-linmiaohe@huawei.com>
On Mon, May 30, 2022 at 07:30:13PM +0800, Miaohe Lin wrote:
> Commit 3268c63eded4 ("mm: fix move/migrate_pages() race on task struct")
> extends the period of the rcu_read_lock until after the permissions checks
> are done to prevent the task pointed to from changing from under us. But
> the task_struct refcount is also taken at that time, the reference to task
> is guaranteed to be stable. So it's unnecessary to extend the period of
> the rcu_read_lock. Release the rcu lock after task refcount is successfully
> grabbed to reduce the rcu holding time.
But why bother? You know the RCU read lock isn't a "real" lock, right?
next prev parent reply other threads:[~2022-05-31 12:59 UTC|newest]
Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-05-30 11:30 [PATCH v4 0/4] A few cleanup and fixup patches for migration Miaohe Lin
2022-05-30 11:30 ` [PATCH v4 1/4] mm: reduce the rcu lock duration Miaohe Lin
2022-05-31 6:06 ` Ying Huang
2022-05-31 9:01 ` Miaohe Lin
2022-05-31 16:09 ` Eric W. Biederman
2022-06-01 6:33 ` Miaohe Lin
2022-06-01 14:37 ` Eric W. Biederman
2022-06-02 9:22 ` Miaohe Lin
2022-06-03 16:28 ` Eric W. Biederman
2022-06-07 9:19 ` Miaohe Lin
2022-06-18 0:23 ` Andrew Morton
2022-06-18 2:49 ` Miaohe Lin
2022-05-31 12:50 ` David Hildenbrand
2022-05-31 12:58 ` Matthew Wilcox [this message]
2022-05-31 13:05 ` Matthew Wilcox
2022-06-01 3:21 ` Miaohe Lin
2022-05-30 11:30 ` [PATCH v4 2/4] mm/migration: remove unneeded lock page and PageMovable check Miaohe Lin
2022-05-31 12:50 ` David Hildenbrand
2022-05-30 11:30 ` [PATCH v4 3/4] mm/migration: return errno when isolate_huge_page failed Miaohe Lin
2022-05-30 11:30 ` [PATCH v4 4/4] mm/migration: fix potential pte_unmap on an not mapped pte Miaohe Lin
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