From: Wei Yang <richardw.yang@linux.intel.com>
To: Michal Hocko <mhocko@kernel.org>
Cc: Wei Yang <richardw.yang@linux.intel.com>,
hannes@cmpxchg.org, vdavydov.dev@gmail.com,
akpm@linux-foundation.org, kirill.shutemov@linux.intel.com,
cgroups@vger.kernel.org, linux-mm@kvack.org,
linux-kernel@vger.kernel.org, yang.shi@linux.alibaba.com
Subject: Re: [RFC PATCH] mm: thp: grab the lock before manipulation defer list
Date: Wed, 8 Jan 2020 08:35:43 +0800 [thread overview]
Message-ID: <20200108003543.GA13943@richard> (raw)
In-Reply-To: <20200107083808.GC32178@dhcp22.suse.cz>
On Tue, Jan 07, 2020 at 09:38:08AM +0100, Michal Hocko wrote:
>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?
Just one confusion, is this kind of description basic concept of concurrent
programming? How detail level we need to describe the effect?
To me, grab the lock before accessing the critical section is obvious.
list_empty and list_del should be the critical section. And the
lock should protect the whole critical section instead of part of it.
>--
>Michal Hocko
>SUSE Labs
--
Wei Yang
Help you, Help me
next prev parent reply other threads:[~2020-01-08 0:35 UTC|newest]
Thread overview: 24+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-01-03 14:34 [RFC PATCH] mm: thp: grab the lock before manipulation defer list Wei Yang
2020-01-03 19:29 ` David Rientjes
2020-01-03 19:29 ` David Rientjes
2020-01-03 23:39 ` Wei Yang
2020-01-04 0:44 ` David Rientjes
2020-01-04 0:44 ` David Rientjes
2020-01-06 1:20 ` Wei Yang
2020-01-06 10:23 ` Michal Hocko
2020-01-07 1:22 ` Wei Yang
2020-01-07 8:38 ` Michal Hocko
2020-01-08 0:35 ` Wei Yang [this message]
2020-01-08 9:40 ` Michal Hocko
2020-01-09 2:03 ` Wei Yang
2020-01-09 8:34 ` Michal Hocko
2020-01-09 2:03 ` Wei Yang
2020-01-09 3:18 ` Wei Yang
2020-01-09 8:36 ` Michal Hocko
2020-01-09 8:52 ` Wei Yang
2020-01-06 16:18 ` Alexander Duyck
2020-01-06 16:18 ` Alexander Duyck
2020-01-07 1:26 ` Wei Yang
2020-01-07 2:07 ` David Rientjes
2020-01-07 2:07 ` David Rientjes
2020-01-07 2:33 ` Wei Yang
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20200108003543.GA13943@richard \
--to=richardw.yang@linux.intel.com \
--cc=akpm@linux-foundation.org \
--cc=cgroups@vger.kernel.org \
--cc=hannes@cmpxchg.org \
--cc=kirill.shutemov@linux.intel.com \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-mm@kvack.org \
--cc=mhocko@kernel.org \
--cc=vdavydov.dev@gmail.com \
--cc=yang.shi@linux.alibaba.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.