From: Andi Kleen <ak@suse.de>
To: Alan Stern <stern@rowland.harvard.edu>
Cc: Chandra Seetharaman <sekharan@us.ibm.com>,
Keith Owens <kaos@ocs.com.au>,
dipankar@in.ibm.com,
Kernel development list <linux-kernel@vger.kernel.org>
Subject: Re: Notifier chains are unsafe
Date: Wed, 26 Oct 2005 23:44:37 +0200 [thread overview]
Message-ID: <200510262344.37982.ak@suse.de> (raw)
In-Reply-To: <Pine.LNX.4.44L0.0510261636580.7186-100000@iolanthe.rowland.org>
On Wednesday 26 October 2005 22:40, Alan Stern wrote:
l> On Wed, 26 Oct 2005, Andreas Kleen wrote:
>
> > > Note that the RCU documentation says RCU critical sections are not
> > > allowed
> > > to sleep.
> >
> > In this case it would be ok.
>
> I don't understand. If it's okay for an RCU critical section to sleep in
> this case, why wouldn't it be okay always? What's special here?
>
> Aren't there requirements about critical sections finishing on the same
> CPU as they started on?
Like I wrote earlier: as long as the notifier doesn't unregister itself
the critical RCU section for the list walk is only a small part of notifier_call_chain.
It's basically a stable anchor in the list that won't change.
The only change needed would be to make these parts unpreemptable and of course
add a RCU step during unregistration.
-Andi
next prev parent reply other threads:[~2005-10-26 21:43 UTC|newest]
Thread overview: 34+ messages / expand[flat|nested] mbox.gz Atom feed top
2005-10-24 20:48 Notifier chains are unsafe Alan Stern
2005-10-25 16:59 ` Joe Seigh
2005-10-25 23:30 ` Chandra Seetharaman
2005-10-26 18:46 ` Alan Stern
2005-10-26 19:05 ` Andreas Kleen
2005-10-26 20:40 ` Alan Stern
2005-10-26 21:44 ` Andi Kleen [this message]
2005-10-26 23:20 ` Chandra Seetharaman
2005-10-27 1:17 ` Joe Seigh
2005-10-28 1:36 ` Chandra Seetharaman
2005-10-27 14:13 ` Alan Stern
2005-10-26 22:40 ` Chandra Seetharaman
2005-10-27 15:28 ` Alan Stern
2005-10-27 20:43 ` Chandra Seetharaman
2005-10-27 21:21 ` Alan Stern
2005-10-27 23:02 ` Chandra Seetharaman
2005-10-28 0:48 ` Keith Owens
2005-10-28 1:34 ` Chandra Seetharaman
2005-10-28 14:23 ` Alan Stern
2005-10-28 22:15 ` Chandra Seetharaman
2005-10-29 14:51 ` Alan Stern
2005-10-31 22:22 ` Chandra Seetharaman
2005-11-01 15:24 ` Alan Stern
2005-11-01 20:20 ` Chandra Seetharaman
2005-11-01 21:20 ` Alan Stern
2005-11-02 9:50 ` Keith Owens
2005-11-02 16:03 ` Alan Stern
[not found] ` <mailman.1130460600.30060.linux-kernel2news@redhat.com>
2005-10-28 4:35 ` Pete Zaitcev
2005-10-25 23:43 ` Andi Kleen
2005-10-26 0:01 ` Chandra Seetharaman
2005-10-26 17:11 ` Andreas Kleen
2005-10-27 2:46 ` Herbert Xu
2005-10-29 12:25 ` Joe Seigh
2005-10-26 6:11 ` Keith Owens
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