From: Dipankar Sarma <dipankar@in.ibm.com>
To: Oleg Nesterov <oleg@tv-sign.ru>
Cc: "Paul E. McKenney" <paulmck@us.ibm.com>,
Srivatsa Vaddagiri <vatsa@in.ibm.com>,
Andrew Morton <akpm@osdl.org>,
linux-kernel@vger.kernel.org
Subject: Re: rcu_do_batch: rcu_data->qlen is not irq safe
Date: Mon, 11 Sep 2006 02:28:27 +0530 [thread overview]
Message-ID: <20060910205827.GD4690@in.ibm.com> (raw)
In-Reply-To: <20060910150820.GA7433@oleg>
On Sun, Sep 10, 2006 at 07:08:20PM +0400, Oleg Nesterov wrote:
> rcu_do_batch() decrements rdp->qlen with irqs enabled.
> This is not good, it can also be modified by call_rcu()
> from interrupt.
>
> So, is it worth fixing? The problem is mostly theoretical.
I think we should fix it even though the problem is theoritical.
> If yes, is it ok to use local_t ? Iirc, the were some
> problems with local_t on some arches. Sometimes it is
> just atomic_t ...
AFAIK, x86 local_t is atomic. Not good.
>
> Otherwise, we can update ->qlen after the main loop,
>
> local_irq_disable();
> rdp->qlen -= count;
> local_irq_enable();
>
> What dou you think?
We should do this.
Thanks
Dipankar
next prev parent reply other threads:[~2006-09-10 20:58 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2006-09-10 15:08 rcu_do_batch: rcu_data->qlen is not irq safe Oleg Nesterov
2006-09-10 20:58 ` Dipankar Sarma [this message]
2006-09-10 21:27 ` Oleg Nesterov
2006-09-10 21:32 ` [PATCH] rcu_do_batch: make ->qlen decrement " Oleg Nesterov
2006-09-10 22:17 ` Dipankar Sarma
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