From: David Miller <davem@davemloft.net>
To: joonwpark81@gmail.com
Cc: netdev@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] [NET]: Fix Ooops of napi net_rx_action.
Date: Tue, 11 Dec 2007 02:32:18 -0800 (PST) [thread overview]
Message-ID: <20071211.023218.31965443.davem@davemloft.net> (raw)
In-Reply-To: <001801c83bd6$2001d410$9c94fea9@jason>
From: "Joonwoo Park" <joonwpark81@gmail.com>
Date: Tue, 11 Dec 2007 18:13:34 +0900
Joonwoo-ssi annyoung haseyo,
> [NET]: Fix Ooops of napi net_rx_action.
> Before doing list_move_tail napi poll_list, it should be ensured
>
> Signed-off-by: Joonwoo Park <joonwpark81@gmail.com>
> ---
> diff --git a/net/core/dev.c b/net/core/dev.c
> index 86d6261..74bd5ab 100644
> --- a/net/core/dev.c
> +++ b/net/core/dev.c
> @@ -2207,7 +2207,8 @@ static void net_rx_action(struct softirq_action *h)
> * still "owns" the NAPI instance and therefore can
> * move the instance around on the list at-will.
> */
> - if (unlikely(work == weight))
> + if (unlikely((test_bit(NAPI_STATE_SCHED, &n->state))
> + && (work == weight)))
> list_move_tail(&n->poll_list, list);
>
> netpoll_poll_unlock(have);
How can the NAPI_STATE_SCHED bit be cleared externally yet we take
this list_move_tail() code path?
If NAPI_STATE_SCHED is cleared, work will be zero which will never be
equal to 'weight', and this we'll never attempt the list_move_tail().
If something clears NAPI_STATE_SCHED meanwhile, we have a serious race
and your patch is an incomplete bandaid. For example, if it can
happen, then a case like:
if (test_bit(NAPI_STATE_SCHED, &n->state))
... something clears NAPI_STATE_SCHED right now ...
work = n->poll(n, weight);
can crash too.
next prev parent reply other threads:[~2007-12-11 10:32 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2007-12-11 9:13 [PATCH] [NET]: Fix Ooops of napi net_rx_action Joonwoo Park
2007-12-11 10:32 ` David Miller [this message]
2007-12-11 12:36 ` Herbert Xu
2007-12-11 12:41 ` David Miller
2007-12-11 12:57 ` Joonwoo Park
2007-12-11 23:12 ` Brandeburg, Jesse
2007-12-11 23:27 ` Joonwoo Park
2007-12-11 23:42 ` Stephen Hemminger
2007-12-16 21:35 ` David Miller
2007-12-12 0:12 ` Joonwoo Park
2007-12-12 0:38 ` Brandeburg, Jesse
2007-12-12 15:12 ` David Miller
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