netdev - Re: [PATCH] netpoll: Don't call driver methods from interrupt context.

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Date:	Mon, 3 Mar 2014 20:23:03 -0800
From:	Cong Wang <xiyou.wangcong@...il.com>
To:	"Eric W. Biederman" <ebiederm@...ssion.com>
Cc:	David Miller <davem@...emloft.net>,
	Linux Kernel Network Developers <netdev@...r.kernel.org>,
	Matt Mackall <mpm@...enic.com>,
	Satyam Sharma <satyam.sharma@...il.com>
Subject: Re: [PATCH] netpoll: Don't call driver methods from interrupt context.

On Mon, Mar 3, 2014 at 12:40 PM, Eric W. Biederman
<ebiederm@...ssion.com> wrote:
>  net/core/netpoll.c |    6 +++---
>  1 files changed, 3 insertions(+), 3 deletions(-)
>
> diff --git a/net/core/netpoll.c b/net/core/netpoll.c
> index a664f7829a6d..a1877621bf31 100644
> --- a/net/core/netpoll.c
> +++ b/net/core/netpoll.c
> @@ -330,7 +330,7 @@ repeat:
>                 skb = skb_dequeue(&skb_pool);
>
>         if (!skb) {
> -               if (++count < 10) {
> +               if (++count < 10 && !in_irq()) {
>                         netpoll_poll_dev(np->dev);

This looks like a workaround.

Here ou are trying to avoid calling netpoll_poll_dev()
in IRQ context, but it has a side effect for netpoll_send_udp()
which could possibly return early after find_skb().

Also, netpoll_poll_dev() does more than just calling driver
poll method, I am not sure if it is safe to skip it either.

netpoll code needs to rewrite.

Thanks.
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