From: Stephen Hemminger <shemminger@vyatta•com>
To: Jay Vosburgh <fubar@us•ibm.com>
Cc: Mitsuo Hayasaka <mitsuo.hayasaka.hu@hitachi•com>,
Andy Gospodarek <andy@greyhouse•net>,
netdev@vger•kernel.org, linux-kernel@vger•kernel.org,
yrl.pp-manager.tt@hitachi•com,
WANG Cong <xiyou.wangcong@gmail•com>
Subject: Re: [PATCH net -v2] [BUGFIX] bonding: use flush_delayed_work_sync in bond_close
Date: Wed, 19 Oct 2011 11:41:29 -0700 [thread overview]
Message-ID: <20111019114129.162d895a@nehalam.linuxnetplumber.net> (raw)
In-Reply-To: <27007.1319047262@death>
On Wed, 19 Oct 2011 11:01:02 -0700
Jay Vosburgh <fubar@us•ibm.com> wrote:
> Mitsuo Hayasaka <mitsuo.hayasaka.hu@hitachi•com> wrote:
>
> >The bond_close() calls cancel_delayed_work() to cancel delayed works.
> >It, however, cannot cancel works that were already queued in workqueue.
> >The bond_open() initializes work->data, and proccess_one_work() refers
> >get_work_cwq(work)->wq->flags. The get_work_cwq() returns NULL when
> >work->data has been initialized. Thus, a panic occurs.
> >
> >This patch uses flush_delayed_work_sync() instead of cancel_delayed_work()
> >in bond_close(). It cancels delayed timer and waits for work to finish
> >execution. So, it can avoid the null pointer dereference due to the
> >parallel executions of proccess_one_work() and initializing proccess
> >of bond_open().
>
> I'm setting up to test this. I have a dim recollection that we
> tried this some years ago, and there was a different deadlock that
> manifested through the flush path. Perhaps changes since then have
> removed that problem.
>
> -J
Won't this deadlock on RTNL. The problem is that:
CPU0 CPU1
rtnl_lock
bond_close
delayed_work
mii_work
read_lock(bond->lock);
read_unlock(bond->lock);
rtnl_lock... waiting for CPU0
flush_delayed_work_sync
waiting for delayed_work to finish...
next prev parent reply other threads:[~2011-10-19 18:41 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-10-19 8:17 [PATCH net -v2] [BUGFIX] bonding: use flush_delayed_work_sync in bond_close Mitsuo Hayasaka
2011-10-19 18:01 ` Jay Vosburgh
2011-10-19 18:41 ` Stephen Hemminger [this message]
2011-10-19 19:09 ` Jay Vosburgh
2011-10-21 5:45 ` Américo Wang
2011-10-21 6:26 ` Jay Vosburgh
2011-10-22 0:59 ` Jay Vosburgh
2011-10-24 4:00 ` HAYASAKA Mitsuo
2011-10-26 17:31 ` Jay Vosburgh
2011-10-28 1:52 ` HAYASAKA Mitsuo
2011-10-28 3:15 ` David Miller
2011-10-29 1:42 ` [PATCH net-next] bonding: eliminate bond_close race conditions Jay Vosburgh
2011-10-30 7:13 ` David Miller
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