netdev - Re: [PATCH net-next] net_sched: act_bpf: remove spinlock in fast path

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Date:	Tue, 4 Aug 2015 09:35:21 -0700
From:	Alexei Starovoitov <ast@...mgrid.com>
To:	Daniel Borkmann <daniel@...earbox.net>
Cc:	"David S. Miller" <davem@...emloft.net>,
	Eric Dumazet <edumazet@...gle.com>,
	Jiri Pirko <jiri@...nulli.us>, netdev@...r.kernel.org
Subject: Re: [PATCH net-next] net_sched: act_bpf: remove spinlock in fast path

On 8/4/15 1:55 AM, Daniel Borkmann wrote:
> Okay, what happens however, when we have an action attached to a
> classifier and do a replace on that action, meaning one CPU is still
> executing the filter inside tcf_bpf(), while another one is already
> running tcf_bpf_cfg_cleanup() on that prog? Afaik, the schedule_work()
> that's called during freeing maps/progs might 'mitigate' this race,
> but doesn't give a hard guarantee, right?

ahh, yes, that's completely different race. tcf_bpf_cfg_cleanup should
be doing call_rcu.
Will respin the patch.

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