From: Zach Brown <zab@redhat.com>
To: Kent Overstreet <koverstreet@google.com>
Cc: linux-bcache@vger.kernel.org, linux-kernel@vger.kernel.org,
dm-devel@redhat.com, tytso@mit.edu
Subject: Re: [PATCH 5/5] aio: Refactor aio_read_evt, use cmxchg(), fix bug
Date: Tue, 9 Oct 2012 11:37:53 -0700 [thread overview]
Message-ID: <20121009183753.GP26187@lenny.home.zabbo.net> (raw)
In-Reply-To: <1349764760-21093-5-git-send-email-koverstreet@google.com>
On Mon, Oct 08, 2012 at 11:39:20PM -0700, Kent Overstreet wrote:
> Bunch of cleanup
Ugh. That's way too much noisy change for one patch with no
description. Break it up into functional pieces and actually describe
them.
> events off the ringbuffer without racing with io_getevents().
Are you sure this is safe in the presence of wrapping indices? It's
been a very long time since I've looked at this, but I could never
convince myself that it was safe.
What I'm worried about is cmpxchg()s caller sampling, say, and index of
0, having another task GO NUTS and wrap that index all the way around
back to 0, and then having that initial cmpchg() caller see the wrapped
0 index and think that's nothing's changed in the interim.
Is this a problem?
(I wish I could find the comment I wrote in a very old patch to tear out
the mapped ring entirely.. It was a great list of its design mistakes.)
- z
next prev parent reply other threads:[~2012-10-09 18:38 UTC|newest]
Thread overview: 35+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-10-09 6:39 [PATCH 1/5] aio: Kill return value of aio_complete() Kent Overstreet
2012-10-09 6:39 ` [PATCH 2/5] aio: kiocb_cancel() Kent Overstreet
2012-10-09 18:26 ` Zach Brown
2012-10-09 21:37 ` Kent Overstreet
2012-10-10 11:03 ` Theodore Ts'o
2012-10-10 21:20 ` Zach Brown
2012-10-10 23:21 ` Theodore Ts'o
2012-10-11 2:41 ` Kent Overstreet
2012-10-09 6:39 ` [PATCH 3/5] aio: Rewrite refcounting Kent Overstreet
2012-10-09 18:27 ` Zach Brown
2012-10-09 22:21 ` Kent Overstreet
2012-10-09 22:35 ` Zach Brown
2012-10-10 0:17 ` Kent Overstreet
2012-10-09 6:39 ` [PATCH 4/5] aio: vmap ringbuffer Kent Overstreet
2012-10-09 18:29 ` Zach Brown
2012-10-09 21:31 ` Kent Overstreet
2012-10-09 22:32 ` Zach Brown
2012-10-09 22:44 ` Kent Overstreet
2012-10-09 22:58 ` Zach Brown
2012-10-10 0:16 ` Kent Overstreet
2012-10-10 0:36 ` Zach Brown
2012-10-10 1:09 ` Kent Overstreet
2012-10-09 6:39 ` [PATCH 5/5] aio: Refactor aio_read_evt, use cmxchg(), fix bug Kent Overstreet
2012-10-09 18:37 ` Zach Brown [this message]
2012-10-09 21:27 ` Kent Overstreet
2012-10-09 22:47 ` Zach Brown
2012-10-09 22:55 ` Kent Overstreet
2012-10-09 23:10 ` Zach Brown
2012-10-10 0:06 ` Kent Overstreet
2012-10-10 0:26 ` Zach Brown
2012-10-10 0:47 ` Kent Overstreet
2012-10-10 21:43 ` Zach Brown
2012-10-11 2:51 ` Kent Overstreet
2012-10-11 16:43 ` Zach Brown
2012-10-09 18:25 ` [PATCH 1/5] aio: Kill return value of aio_complete() Zach Brown
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=20121009183753.GP26187@lenny.home.zabbo.net \
--to=zab@redhat.com \
--cc=dm-devel@redhat.com \
--cc=koverstreet@google.com \
--cc=linux-bcache@vger.kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=tytso@mit.edu \
/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).