Jarek Poplawski wrote, On 08/14/2008 01:24 PM:
> On Wed, Aug 13, 2008 at 03:19:18PM -0700, David Miller wrote:

quoted text
> ...

>> Ok, so what I'm going to do is check in my patch and then try

>> to figure out how to resolve this "both bits clear" scenerio.

>

> BTW, here is my older doubt revisited, where I hope to be re-considered/

> re-convinced, if possible...

After problems while testing this by Denys in another thread

I withdraw this patch.
Thanks,

Jarek P.
> ---------------->

quoted text
>

> pkt_sched: Destroy qdiscs under rtnl_lock again.

>

> We don't need to trigger __qdisc_destroy() as an RCU callback because

> the use of qdisc isn't controlled by RCU alone: after querying RCU

> with synchronize_rcu() in dev_deactivate() we additionaly wait in a

> loop checking some flags. After the loop is done there could be no

> outstanding use of the qdisc, so call_rcu() doesn't make any sense.

>

> On the other hand, current calling Qdisc's ->destroy() from a softirq

> context without locking (rtnl) can break various things like:

> qdisc_put_rtab(), tcf_destroy_chain() (e.g. u32_destroy()), and

> probably more.

>

>

> Signed-off-by: Jarek Poplawski

>

> ---

>

>  net/sched/sch_generic.c |    8 ++------

>  1 files changed, 2 insertions(+), 6 deletions(-)

>

> diff --git a/net/sched/sch_generic.c b/net/sched/sch_generic.c

> index 4685746..e7379d2 100644

> --- a/net/sched/sch_generic.c

> +++ b/net/sched/sch_generic.c

> @@ -518,12 +518,8 @@ void qdisc_reset(struct Qdisc *qdisc)

>  }

>  EXPORT_SYMBOL(qdisc_reset);

>

> -/* this is the rcu callback function to clean up a qdisc when there

> - * are no further references to it */

> -

> -static void __qdisc_destroy(struct rcu_head *head)

> +static void __qdisc_destroy(struct Qdisc *qdisc)

>  {

> -	struct Qdisc *qdisc = container_of(head, struct Qdisc, q_rcu);

>  	const struct Qdisc_ops  *ops = qdisc->ops;

>

>  #ifdef CONFIG_NET_SCHED

> @@ -554,7 +550,7 @@ void qdisc_destroy(struct Qdisc *qdisc)

>  	if (qdisc->parent)

>  		list_del(&qdisc->list);

>

> -	call_rcu(&qdisc->q_rcu, __qdisc_destroy);

> +	__qdisc_destroy(qdisc);

>  }

>  EXPORT_SYMBOL(qdisc_destroy);

>

> --

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