From: Tejun Heo <tj@kernel.org>
To: Andy Walls <awalls@md.metrocast.net>
Cc: linux-kernel@vger.kernel.org,
Andrew Morton <akpm@linux-foundation.org>,
Avi Kivity <avi@redhat.com>,
kvm@vger.kernel.org, ivtv-devel@ivtvdriver.org,
linux-media@vger.kernel.org,
Grant Likely <grant.likely@secretlab.ca>,
spi-devel-general@lists.sourceforge.net,
Linus Torvalds <torvalds@linux-foundation.org>
Subject: Re: [PATCH 2/2] kthread_worker: reimplement flush_kthread_work() to allow freeing the work item being executed
Date: Mon, 23 Jul 2012 10:12:15 -0700 [thread overview]
Message-ID: <20120723171215.GA5776@google.com> (raw)
In-Reply-To: <1342990015.2487.19.camel@palomino.walls.org>
Hello,
On Sun, Jul 22, 2012 at 04:46:54PM -0400, Andy Walls wrote:
> Hmmm, I didn't know about the constraint about 'known to be alive' in
> the other email I just sent.
>
> That might make calling flush_kthread_work() hard for a user to use, if
> the user lets the work get freed by another thread executing the work.
Umm... flushing a freed work item doesn't make any sense at all. The
pointer itself loses the ability to identify anything. What if it
gets recycled to another work item which happens to depend on the
flusher to make forward progress? You now have a circular dependency
through a recycled memory area. Good luck hunting that down.
For pretty much any API, allowing dangling pointers as argument is
insane. If you want to flush self-freeing work items, flush the
kthread_worker. That's how it is with workqueue and how it should be
with kthread_worker too.
Thanks.
--
tejun
next prev parent reply other threads:[~2012-07-23 17:12 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-07-19 21:15 [PATCHSET] kthread_worker: reimplement flush_kthread_work() to allow freeing during execution Tejun Heo
[not found] ` <20120719211510.GA32763-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org>
2012-07-19 21:15 ` [PATCH 1/2] kthread_worker: reorganize to prepare for flush_kthread_work() reimplementation Tejun Heo
2012-07-21 17:13 ` Andy Walls
2012-07-22 16:46 ` Tejun Heo
[not found] ` <20120722164607.GB5144-RcKxWJ4Cfj1J2suj2OqeGauc2jM2gXBXkQQo+JxHRPFibQn6LdNjmg@public.gmane.org>
2012-07-22 20:42 ` Andy Walls
2012-07-22 17:22 ` [PATCH UPDATED " Tejun Heo
2012-07-19 21:16 ` [PATCH 2/2] kthread_worker: reimplement flush_kthread_work() to allow freeing the work item being executed Tejun Heo
[not found] ` <20120719211629.GC32763-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org>
2012-07-21 18:20 ` Andy Walls
[not found] ` <1342894814.2504.31.camel-xioobY1GIEhKttHedORAlB2eb7JE58TQ@public.gmane.org>
2012-07-22 16:49 ` Tejun Heo
[not found] ` <20120722164953.GC5144-RcKxWJ4Cfj1J2suj2OqeGauc2jM2gXBXkQQo+JxHRPFibQn6LdNjmg@public.gmane.org>
2012-07-22 20:46 ` Andy Walls
2012-07-23 17:12 ` Tejun Heo [this message]
[not found] ` <20120723171215.GA5776-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org>
2012-07-24 11:17 ` Andy Walls
2012-07-22 20:39 ` Andy Walls
2012-09-14 22:50 ` [PATCHSET] kthread_worker: reimplement flush_kthread_work() to allow freeing during execution Colin Cross
2012-09-17 19:40 ` Tejun Heo
2012-09-17 20:28 ` Greg KH
[not found] ` <20120917202850.GA18910-U8xfFu+wG4EAvxtiuMwx3w@public.gmane.org>
2012-09-28 0:19 ` Greg KH
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=20120723171215.GA5776@google.com \
--to=tj@kernel.org \
--cc=akpm@linux-foundation.org \
--cc=avi@redhat.com \
--cc=awalls@md.metrocast.net \
--cc=grant.likely@secretlab.ca \
--cc=ivtv-devel@ivtvdriver.org \
--cc=kvm@vger.kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-media@vger.kernel.org \
--cc=spi-devel-general@lists.sourceforge.net \
--cc=torvalds@linux-foundation.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;
as well as URLs for NNTP newsgroup(s).