linux-kernel.vger.kernel.org archive mirror
 help / color / mirror / Atom feed
From: Michal Hocko <mhocko@kernel.org>
To: "Kirill A. Shutemov" <kirill@shutemov.name>
Cc: Wei Yang <richardw.yang@linux.intel.com>,
	hannes@cmpxchg.org, vdavydov.dev@gmail.com,
	akpm@linux-foundation.org, cgroups@vger.kernel.org,
	linux-mm@kvack.org, linux-kernel@vger.kernel.org,
	kirill.shutemov@linux.intel.com, yang.shi@linux.alibaba.com,
	alexander.duyck@gmail.com, rientjes@google.com
Subject: Re: [Patch v2] mm: thp: grab the lock before manipulation defer list
Date: Tue, 14 Jan 2020 10:31:22 +0100	[thread overview]
Message-ID: <20200114093122.GH19428@dhcp22.suse.cz> (raw)
In-Reply-To: <20200111000352.efy6krudecpshezh@box>

On Sat 11-01-20 03:03:52, Kirill A. Shutemov wrote:
> On Thu, Jan 09, 2020 at 10:30:54PM +0800, Wei Yang wrote:
> > As all the other places, we grab the lock before manipulate the defer list.
> > Current implementation may face a race condition.
> > 
> > For example, the potential race would be:
> > 
> >     CPU1                      CPU2
> >     mem_cgroup_move_account   split_huge_page_to_list
> >       !list_empty
> >                                 lock
> >                                 !list_empty
> >                                 list_del
> >                                 unlock
> >       lock
> >       # !list_empty might not hold anymore
> >       list_del_init
> >       unlock
> 
> I don't think this particular race is possible. Both parties take page
> lock before messing with deferred queue, but anytway:
> 
> Acked-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>

I am confused, if the above race is not possible then what would be a
real race? We really do not want to have a patch with a misleading
changelog, do we?
-- 
Michal Hocko
SUSE Labs

  parent reply	other threads:[~2020-01-14  9:31 UTC|newest]

Thread overview: 16+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-01-09 14:30 [Patch v2] mm: thp: grab the lock before manipulation defer list Wei Yang
2020-01-09 18:52 ` David Rientjes
2020-01-09 18:58 ` Michal Hocko
2020-01-11  0:03 ` Kirill A. Shutemov
2020-01-12  2:28   ` Wei Yang
2020-01-12 22:57     ` Kirill A. Shutemov
2020-01-13  0:44       ` Wei Yang
2020-01-13  7:36         ` Kirill A. Shutemov
2020-01-13  8:23           ` Wei Yang
2020-01-14  9:31   ` Michal Hocko [this message]
2020-01-14 10:31     ` Kirill A. Shutemov
2020-01-14 10:59       ` Kirill A. Shutemov
2020-01-14 20:57         ` David Rientjes
2020-01-15  1:19           ` Wei Yang
2020-01-15  1:07         ` Wei Yang
2020-01-15  3:26           ` David Rientjes

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=20200114093122.GH19428@dhcp22.suse.cz \
    --to=mhocko@kernel.org \
    --cc=akpm@linux-foundation.org \
    --cc=alexander.duyck@gmail.com \
    --cc=cgroups@vger.kernel.org \
    --cc=hannes@cmpxchg.org \
    --cc=kirill.shutemov@linux.intel.com \
    --cc=kirill@shutemov.name \
    --cc=linux-kernel@vger.kernel.org \
    --cc=linux-mm@kvack.org \
    --cc=richardw.yang@linux.intel.com \
    --cc=rientjes@google.com \
    --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 a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).