Re: Question on 5.4.55 merge into 5.4-rt

[Sebastian Andrzej Siewior]

On 2020-08-14 18:54:21 [-0400], Steven Rostedt wrote:
> 
> When merging 5.4.55 into 5.4-rt I hit the following conflict:
…
> 
> Where we are doing something slightly different. Placing the skb on the
> sd->tofree_queue and raising NET_RX_SOFTIQ instead.
> 
> Now that the vanilla stable 5.4 kernel doesn't call kfree_skb() from
> irqs_disabled, can I safely revert this entire change?

Not if you mean dropping skbufhead-raw-lock.patch.

We can drop `tofree_queue' and everything related to it. We need to
keep the `raw_lock' and the `rps_lock()' hunks for
`sd->input_pkt_queue'. The other queue, `sd->process_queue', is
protected by local_bh_disable() so these hunks can be dropped in the
more recent RT versions with the re-written softirq code
(v5.0.19-rt10+).

> Is it safe to call kfree_skb() from local_bh_disable()?

of course it is.

> I'm assuming it is, but just want to clarify. I'll be continuing
> merging latest stable (with this revert), but please yell if you think
> it will break?
>
> Thanks!
> 
> -- Steve

Sebastian