From: Matthew Wilcox <willy@infradead.org>
To: Christopher Lameter <cl@linux.com>
Cc: Eric Dumazet <eric.dumazet@gmail.com>,
linux-mm@kvack.org, Matthew Wilcox <mawilcox@microsoft.com>,
Pekka Enberg <penberg@kernel.org>,
David Rientjes <rientjes@google.com>,
Joonsoo Kim <iamjoonsoo.kim@lge.com>,
Andrew Morton <akpm@linux-foundation.org>,
linux-kernel@vger.kernel.org, Jan Kara <jack@suse.cz>,
Jeff Layton <jlayton@redhat.com>,
Mel Gorman <mgorman@techsingularity.net>,
stable@vger.kernel.org
Subject: Re: [PATCH 1/2] slab: __GFP_ZERO is incompatible with a constructor
Date: Tue, 10 Apr 2018 10:50:12 -0700 [thread overview]
Message-ID: <20180410175011.GE3614@bombadil.infradead.org> (raw)
In-Reply-To: <alpine.DEB.2.20.1804101244290.29559@nuc-kabylake>
On Tue, Apr 10, 2018 at 12:45:56PM -0500, Christopher Lameter wrote:
> On Tue, 10 Apr 2018, Matthew Wilcox wrote:
>
> > > How do you envision dealing with the SLAB_TYPESAFE_BY_RCU slab caches?
> > > Those must have a defined state of the objects at all times and a constructor is
> > > required for that. And their use of RCU is required for numerous lockless
> > > lookup algorithms in the kernhel.
> >
> > Not at all times. Only once they've been used. Re-constructing them
> > once they've been used might break the rcu typesafety, I suppose ...
> > would need to examine the callers.
>
> Objects can be freed and reused and still be accessed from code that
> thinks the object is the old and not the new object....
Yes, I know, that's the point of RCU typesafety. My point is that an
object *which has never been used* can't be accessed. So you don't *need*
a constructor.
next prev parent reply other threads:[~2018-04-10 17:50 UTC|newest]
Thread overview: 22+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-04-10 12:53 Matthew Wilcox
2018-04-10 12:53 ` [PATCH 2/2] page cache: Mask off unwanted GFP flags Matthew Wilcox
2018-04-10 13:08 ` Johannes Weiner
2018-04-10 13:09 ` Michal Hocko
2018-04-10 13:45 ` Minchan Kim
2018-04-10 14:02 ` Matthew Wilcox
2018-04-10 15:18 ` Jaegeuk Kim
2018-04-10 13:46 ` Jan Kara
2018-04-10 13:00 ` [PATCH 1/2] slab: __GFP_ZERO is incompatible with a constructor Johannes Weiner
2018-04-10 13:07 ` Michal Hocko
2018-04-10 13:40 ` Vlastimil Babka
2018-04-10 13:53 ` Eric Dumazet
2018-04-10 16:50 ` Matthew Wilcox
2018-04-10 17:30 ` Christopher Lameter
2018-04-10 17:38 ` Matthew Wilcox
2018-04-10 17:45 ` Christopher Lameter
2018-04-10 17:50 ` Matthew Wilcox [this message]
2018-04-10 20:21 ` Christopher Lameter
2018-04-10 14:21 ` Christopher Lameter
2018-04-10 14:26 ` Christopher Lameter
2018-04-10 15:54 ` Matthew Wilcox
2018-04-10 17:04 ` Christopher Lameter
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=20180410175011.GE3614@bombadil.infradead.org \
--to=willy@infradead.org \
--cc=akpm@linux-foundation.org \
--cc=cl@linux.com \
--cc=eric.dumazet@gmail.com \
--cc=iamjoonsoo.kim@lge.com \
--cc=jack@suse.cz \
--cc=jlayton@redhat.com \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-mm@kvack.org \
--cc=mawilcox@microsoft.com \
--cc=mgorman@techsingularity.net \
--cc=penberg@kernel.org \
--cc=rientjes@google.com \
--cc=stable@vger.kernel.org \
/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