Re: [PATCH] bpf: Convert lpm_trie::lock to 'raw_spinlock_t'

[Sebastian Sewior <bigeasy@linutronix.de>]

On 2024-11-10 10:08:00 [+0800], Hou Tao wrote:
> >> well. However, after changing the kmalloc and its variants to bpf memory
> >> allocator, I think the switch to raw_spinlock_t will be safe. I have
> >> already written a draft patch set. Will post after after polishing and
> >> testing it. WDYT ?
> > Switching lpm to bpf_mem_alloc would address the issue.
> > Why do you want a switch to raw_spin_lock as well?
> > kfree_rcu() is already done outside of the lock.
> 
> After switching to raw_spinlock_t, the lpm trie could be used under
> interrupt context even under PREEMPT_RT.

I would have to dig why the lock has been moved away from raw_spinlock_t
and why we need it back and what changed since. I have some vague memory
that there was a test case which added plenty of items and cleaning it
up created latency spikes.
Note that interrupts are threaded on PREEMPT_RT. Using it in "interrupt
context" would mean you need this in the primary handler/ hardirq.

Sebastian