linux-kernel - Re: [PATCH] cpuset: current_cpuset_is_being

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-Id: <20100312085807.950B.A69D9226@jp.fujitsu.com>
Date:	Fri, 12 Mar 2010 09:03:03 +0900 (JST)
From:	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>
To:	paulmck@...ux.vnet.ibm.com
Cc:	kosaki.motohiro@...fujitsu.com, Miao Xie <miaox@...fujitsu.com>,
	Paul Menage <menage@...gle.com>,
	David Rientjes <rientjes@...gle.com>,
	Li Zefan <lizf@...fujitsu.com>, Nick Piggin <npiggin@...e.de>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] cpuset: current_cpuset_is_being_rebound() need rcu lock

> On Thu, Mar 11, 2010 at 02:46:15PM +0900, KOSAKI Motohiro wrote:
> > rcu lockdep detected cpuset have wrong rcu usage.
> > the fixing is trivial. but I wonder why don't cpuset_being_rebound assignment
> > and read need a memory barrier pairing?
> 
> The fix is in -tip, commit 99ee4ca746dda71326db7645463b4075ac1d665c.
> 
> This is an initialization-time use of rcu_dereference(), so no other
> task has a reference to this data.  Hence it is constant.  Other uses
> of this code operate on shared data structures, which might change at
> any time.

thanks. I haven't notice such commit.

I think you are talking about task_cs(current) accessing and you are right
in such point.
but I'm talking cpuset_being_rebound global variable.

update_tasks_nodemask() has following code

static void update_tasks_nodemask(struct cpuset *cs, const nodemask_t *oldmem,
                                 struct ptr_heap *heap)
{
        cpuset_being_rebound = cs;		/* start transaction */
        cgroup_scan_tasks(&scan);
        cpuset_being_rebound = NULL;		/* end transaction */
}



--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/