From: "HORIGUCHI NAOYA(堀口 直也)" <naoya.horiguchi@nec.com>
To: Miaohe Lin <linmiaohe@huawei.com>
Cc: Naoya Horiguchi <nao.horiguchi@gmail.com>,
Andrew Morton <akpm@linux-foundation.org>,
David Hildenbrand <david@redhat.com>,
Oscar Salvador <osalvador@suse.de>,
Michal Hocko <mhocko@suse.com>, Ding Hui <dinghui@sangfor.com.cn>,
Tony Luck <tony.luck@intel.com>,
Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
Linux-MM <linux-mm@kvack.org>
Subject: Re: [PATCH v1 1/6] mm/hwpoison: mf_mutex for soft offline and unpoison
Date: Wed, 16 Jun 2021 00:41:30 +0000 [thread overview]
Message-ID: <20210616004129.GB1924716@hori.linux.bs1.fc.nec.co.jp> (raw)
In-Reply-To: <e41ea6bf-9d0b-c459-8a77-f7981c6f50c3@huawei.com>
On Tue, Jun 15, 2021 at 08:42:23PM +0800, Miaohe Lin wrote:
...
> > @@ -1960,7 +1964,7 @@ int unpoison_memory(unsigned long pfn)
> > if (!PageHuge(page) && PageTransHuge(page)) {
> > unpoison_pr_info("Unpoison: Memory failure is now running on %#lx\n",
> > pfn, &unpoison_rs);
> > - return 0;
> > + goto unlock_mutex;
> > }
> >
>
> Maybe it's more appropriate to start mutex_lock(&mf_mutex) here? I think these races start here.
Hi Miaohe,
Thank your for the review.
Consider that we put mutex_lock() here, and let's think about two concurrent
calls of unpoison_memory(), then these events could be processed like below:
CPU 0 CPU 1
unpoison_memory
check PageHWPoison // true
unpoison_memory
check PageHWPoison // true
mutex_lock
get_hwpoison_page
TestClearPageHWPoison
put_page
put_page // freed
mutex_unlock
// the unpoisoned page can be used for allocation
mutex_lock
get_hwpoison_page // succeeds
... // unpoison the !PageHWPoison page !?
So I thought that we had better do the prechecks in mf_mutex. Maybe the 2nd
unpoison_memory() just get and put the page refcount by 1 even in this race,
so the impact is not so big, but I feel like avoiding "unpoison the
!PageHWPoison page" situation.
Does it make sense for you?
Thanks,
Naoya Horiguchi
next prev parent reply other threads:[~2021-06-16 0:41 UTC|newest]
Thread overview: 22+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-06-14 2:12 [PATCH v1 0/6] mm/hwpoison: fix unpoison_memory() Naoya Horiguchi
2021-06-14 2:12 ` [PATCH v1 1/6] mm/hwpoison: mf_mutex for soft offline and unpoison Naoya Horiguchi
2021-06-15 11:41 ` Ding Hui
2021-06-15 11:55 ` HORIGUCHI NAOYA(堀口 直也)
2021-06-15 12:42 ` Miaohe Lin
2021-06-16 0:41 ` HORIGUCHI NAOYA(堀口 直也) [this message]
2021-06-16 3:14 ` Miaohe Lin
2021-06-14 2:12 ` [PATCH v1 2/6] mm/hwpoison: remove race consideration Naoya Horiguchi
2021-06-15 12:57 ` Ding Hui
2021-06-16 0:11 ` HORIGUCHI NAOYA(堀口 直也)
2021-06-16 0:40 ` Ding Hui
2021-06-14 2:12 ` [PATCH v1 3/6] mm/hwpoison: introduce MF_MSG_PAGETABLE Naoya Horiguchi
2021-06-14 3:06 ` Matthew Wilcox
2021-06-14 3:55 ` HORIGUCHI NAOYA(堀口 直也)
2021-06-14 2:12 ` [PATCH v1 4/6] mm/hwpoison: remove MF_MSG_BUDDY_2ND and MF_MSG_POISONED_HUGE Naoya Horiguchi
2021-06-14 2:12 ` [PATCH v1 5/6] mm/hwpoison: make some kernel pages handlable Naoya Horiguchi
2021-07-28 10:59 ` Ding Hui
2021-07-29 6:54 ` HORIGUCHI NAOYA(堀口 直也)
2021-06-14 2:12 ` [PATCH v1 6/6] mm/hwpoison: fix unpoison_memory() Naoya Horiguchi
2021-06-17 10:00 ` Ding Hui
2021-06-18 8:36 ` HORIGUCHI NAOYA(堀口 直也)
2021-06-19 12:22 ` Ding Hui
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