Messages in this thread | | | Date | Tue, 7 Jan 2020 09:38:08 +0100 | From | Michal Hocko <> | Subject | Re: [RFC PATCH] mm: thp: grab the lock before manipulation defer list |
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On Tue 07-01-20 09:22:41, Wei Yang wrote: > On Mon, Jan 06, 2020 at 11:23:45AM +0100, Michal Hocko wrote: > >On Fri 03-01-20 22:34:07, Wei Yang wrote: > >> As all the other places, we grab the lock before manipulate the defer list. > >> Current implementation may face a race condition. > > > >Please always make sure to describe the effect of the change. Why a racy > >list_empty check matters? > > > > Hmm... access the list without proper lock leads to many bad behaviors.
My point is that the changelog should describe that bad behavior.
> For example, if we grab the lock after checking list_empty, the page may > already be removed from list in split_huge_page_list. And then list_del_init > would trigger bug.
And how does list_empty check under the lock guarantee that the page is on the deferred list? -- Michal Hocko SUSE Labs
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