On 2023/9/5 19:59, Dan Carpenter wrote:
> Added netdev because they're really the experts.
>
> On Fri, Aug 25, 2023 at 09:52:10AM +0800, Jinjie Ruan wrote:
>> It is not allowed to call kfree_skb() from hardware interrupt
>> context or with interrupts being disabled.
>
> There are no comments which say that this is not allowed. I have
> reviewed the code to see why it's not allowed. The only thing I can
> see is that maybe the skb->destructor(skb); in skb_release_head_state()
> sleeps? Or possibly the uarg->callback() in skb_zcopy_clear()?
The commit e6247027e517 ("net: introduce dev_consume_skb_any()") has the
below comment:
3830 /*
3831 * It is not allowed to call kfree_skb() or consume_skb() from hardware
3832 * interrupt context or with hardware interrupts being disabled.
3833 * (in_hardirq() || irqs_disabled())
3834 *
3835 * We provide four helpers that can be used in following contexts :
3836 *
3837 * dev_kfree_skb_irq(skb) when caller drops a packet from irq context,
3838 * replacing kfree_skb(skb)
3839 *
3840 * dev_consume_skb_irq(skb) when caller consumes a packet from irq
context.
3841 * Typically used in place of consume_skb(skb) in TX completion path
3842 *
3843 * dev_kfree_skb_any(skb) when caller doesn't know its current irq
context,
3844 * replacing kfree_skb(skb)
3845 *
3846 * dev_consume_skb_any(skb) when caller doesn't know its current
irq context,
3847 * and consumed a packet. Used in place of consume_skb(skb)
3848 */
>
> Can you comment more on why this isn't allowed? Was this detected at
> runtime? Do you have a stack trace?
>
> Once I know more I can add this to Smatch so that it is detected
> automatically using static analysis.
>
> regards,
> dan carpenter
>
>
