Re: [PATCH] drivers/net: fixed drivers that support netpoll use ndo_start_xmit()

[Matt Mackall <mpm@selenic.com>]

On Fri, 2009-08-14 at 13:12 +0800, DDD wrote:
> The NETPOLL API requires that interrupts remain disabled in
> netpoll_send_skb(). The use of spin_lock_irq() and spin_unlock_irq()
> in the NETPOLL API callbacks causes the interrupts to get enabled and
> can lead to kernel instability.
> 
> The solution is to use spin_lock_irqsave() and spin_unlock_restore()
> to prevent the irqs from getting enabled while in netpoll_send_skb().
> 
> Call trace:
> netpoll_send_skb()
> {
>    -> local_irq_save(flags)
>      ---> dev->ndo_start_xmit(skb, dev)
>          ---> spin_lock_irq()
>          ---> spin_unlock_irq() *******here would enable the interrupt.
>               ...
>    -> local_irq_restore(flags)
> }
> 
> Signed-off-by: Dongdong Deng <dongdong.deng@windriver.com>
> Signed-off-by: Jason Wessel <jason.wessel@windriver.com>
> Acked-by: Bruce Ashfield <bruce.ashfield@windriver.com>

Acked-by: Matt Mackall <mpm@selenic.com>

Perhaps we should also have a WARN_ONCE if start_xmit returns with
interrupts enabled?

-- 
http://selenic.com : development and support for Mercurial and Linux