From: Matthew Wilcox <willy@infradead.org>
To: Alex Shi <alex.shi@linux.alibaba.com>
Cc: Konstantin Khlebnikov <khlebnikov@yandex-team.ru>,
cgroups@vger.kernel.org, linux-kernel@vger.kernel.org,
linux-mm@kvack.org, akpm@linux-foundation.org,
mgorman@techsingularity.net, tj@kernel.org, hughd@google.com,
daniel.m.jordan@oracle.com, yang.shi@linux.alibaba.com,
shakeelb@google.com, hannes@cmpxchg.org,
Michal Hocko <mhocko@kernel.org>,
Vladimir Davydov <vdavydov.dev@gmail.com>
Subject: Re: [PATCH v7 02/10] mm/memcg: fold lru_lock in lock_page_lru
Date: Mon, 13 Jan 2020 08:34:56 -0800 [thread overview]
Message-ID: <20200113163456.GA332@bombadil.infradead.org> (raw)
In-Reply-To: <a095d80d-8e34-c84f-e4be-085a5aae1929@linux.alibaba.com>
On Mon, Jan 13, 2020 at 08:47:25PM +0800, Alex Shi wrote:
> 在 2020/1/13 下午5:55, Konstantin Khlebnikov 写道:
> >>> That's wrong. Here PageLRU must be checked again under lru_lock.
> >> Hi, Konstantin,
> >>
> >> For logical remain, we can get the lock and then release for !PageLRU.
> >> but I still can figure out the problem scenario. Would like to give more hints?
> >
> > That's trivial race: page could be isolated from lru between
> >
> > if (PageLRU(page))
> > and
> > spin_lock_irq(&pgdat->lru_lock);
>
> yes, it could be a problem. guess the following change could helpful:
> I will update it in new version.
> + if (lrucare) {
> + lruvec = lock_page_lruvec_irq(page);
> + if (likely(PageLRU(page))) {
> + ClearPageLRU(page);
> + del_page_from_lru_list(page, lruvec, page_lru(page));
> + } else {
> + unlock_page_lruvec_irq(lruvec);
> + lruvec = NULL;
> + }
What about a harder race to hit like a page being on LRU list A when you
look up the lruvec, then it's removed and added to LRU list B by the
time you get the lock? At that point, you are holding a lock on the
wrong LRU list. I think you need to check not just that the page
is still PageLRU but also still on the same LRU list.
WARNING: multiple messages have this Message-ID (diff)
From: Matthew Wilcox <willy-wEGCiKHe2LqWVfeAwA7xHQ@public.gmane.org>
To: Alex Shi <alex.shi-KPsoFbNs7GizrGE5bRqYAgC/G2K4zDHf@public.gmane.org>
Cc: Konstantin Khlebnikov
<khlebnikov-XoJtRXgx1JseBXzfvpsJ4g@public.gmane.org>,
cgroups-u79uwXL29TY76Z2rM5mHXA@public.gmane.org,
linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org,
linux-mm-Bw31MaZKKs3YtjvyW6yDsg@public.gmane.org,
akpm-de/tnXTf+JLsfHDXvbKv3WD2FQJk+8+b@public.gmane.org,
mgorman-3eNAlZScCAx27rWaFMvyedHuzzzSOjJt@public.gmane.org,
tj-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org,
hughd-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org,
daniel.m.jordan-QHcLZuEGTsvQT0dZR+AlfA@public.gmane.org,
yang.shi-KPsoFbNs7GizrGE5bRqYAgC/G2K4zDHf@public.gmane.org,
shakeelb-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org,
hannes-druUgvl0LCNAfugRpC6u6w@public.gmane.org,
Michal Hocko <mhocko-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>,
Vladimir Davydov
<vdavydov.dev-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
Subject: Re: [PATCH v7 02/10] mm/memcg: fold lru_lock in lock_page_lru
Date: Mon, 13 Jan 2020 08:34:56 -0800 [thread overview]
Message-ID: <20200113163456.GA332@bombadil.infradead.org> (raw)
In-Reply-To: <a095d80d-8e34-c84f-e4be-085a5aae1929-KPsoFbNs7GizrGE5bRqYAgC/G2K4zDHf@public.gmane.org>
On Mon, Jan 13, 2020 at 08:47:25PM +0800, Alex Shi wrote:
> 在 2020/1/13 下午5:55, Konstantin Khlebnikov 写道:
> >>> That's wrong. Here PageLRU must be checked again under lru_lock.
> >> Hi, Konstantin,
> >>
> >> For logical remain, we can get the lock and then release for !PageLRU.
> >> but I still can figure out the problem scenario. Would like to give more hints?
> >
> > That's trivial race: page could be isolated from lru between
> >
> > if (PageLRU(page))
> > and
> > spin_lock_irq(&pgdat->lru_lock);
>
> yes, it could be a problem. guess the following change could helpful:
> I will update it in new version.
> + if (lrucare) {
> + lruvec = lock_page_lruvec_irq(page);
> + if (likely(PageLRU(page))) {
> + ClearPageLRU(page);
> + del_page_from_lru_list(page, lruvec, page_lru(page));
> + } else {
> + unlock_page_lruvec_irq(lruvec);
> + lruvec = NULL;
> + }
What about a harder race to hit like a page being on LRU list A when you
look up the lruvec, then it's removed and added to LRU list B by the
time you get the lock? At that point, you are holding a lock on the
wrong LRU list. I think you need to check not just that the page
is still PageLRU but also still on the same LRU list.
next prev parent reply other threads:[~2020-01-13 16:35 UTC|newest]
Thread overview: 44+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-12-25 9:04 [PATCH v7 00/10] per lruvec lru_lock for memcg Alex Shi
2019-12-25 9:04 ` [PATCH v7 01/10] mm/vmscan: remove unnecessary lruvec adding Alex Shi
2020-01-10 8:39 ` Konstantin Khlebnikov
2020-01-13 7:21 ` Alex Shi
2019-12-25 9:04 ` [PATCH v7 02/10] mm/memcg: fold lru_lock in lock_page_lru Alex Shi
2020-01-10 8:49 ` Konstantin Khlebnikov
2020-01-10 8:49 ` Konstantin Khlebnikov
2020-01-13 9:45 ` Alex Shi
2020-01-13 9:45 ` Alex Shi
2020-01-13 9:55 ` Konstantin Khlebnikov
2020-01-13 12:47 ` Alex Shi
2020-01-13 12:47 ` Alex Shi
2020-01-13 16:34 ` Matthew Wilcox [this message]
2020-01-13 16:34 ` Matthew Wilcox
2020-01-14 9:20 ` Alex Shi
2019-12-25 9:04 ` [PATCH v7 03/10] mm/lru: replace pgdat lru_lock with lruvec lock Alex Shi
2019-12-25 9:04 ` Alex Shi
2020-01-13 15:41 ` Daniel Jordan
2020-01-13 15:41 ` Daniel Jordan
2020-01-14 6:33 ` Alex Shi
2020-01-14 6:33 ` Alex Shi
2019-12-25 9:04 ` [PATCH v7 04/10] mm/lru: introduce the relock_page_lruvec function Alex Shi
2019-12-25 9:04 ` [PATCH v7 05/10] mm/mlock: optimize munlock_pagevec by relocking Alex Shi
2019-12-25 9:04 ` [PATCH v7 06/10] mm/swap: only change the lru_lock iff page's lruvec is different Alex Shi
2019-12-25 9:04 ` [PATCH v7 07/10] mm/pgdat: remove pgdat lru_lock Alex Shi
2019-12-25 9:04 ` [PATCH v7 08/10] mm/lru: revise the comments of lru_lock Alex Shi
2019-12-25 9:04 ` Alex Shi
2019-12-25 9:04 ` [PATCH v7 09/10] mm/lru: add debug checking for page memcg moving Alex Shi
2019-12-25 9:04 ` [PATCH v7 10/10] mm/memcg: add debug checking in lock_page_memcg Alex Shi
2019-12-31 23:05 ` [PATCH v7 00/10] per lruvec lru_lock for memcg Andrew Morton
2020-01-02 10:21 ` Alex Shi
2020-01-02 10:21 ` Alex Shi
2020-01-10 2:01 ` Alex Shi
2020-01-13 8:48 ` Hugh Dickins
2020-01-13 8:48 ` Hugh Dickins
2020-01-13 8:48 ` Hugh Dickins
2020-01-13 12:45 ` Alex Shi
2020-01-13 12:45 ` Alex Shi
2020-01-13 20:20 ` Hugh Dickins
2020-01-13 20:20 ` Hugh Dickins
2020-01-13 20:20 ` Hugh Dickins
2020-01-14 9:14 ` Alex Shi
2020-01-14 9:29 ` Alex Shi
2020-01-14 9:29 ` Alex Shi
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