From: Daniel Borkmann <daniel@iogearbox.net>
To: Alexei Starovoitov <ast@plumgrid.com>
Cc: "David S. Miller" <davem@davemloft.net>,
Eric Dumazet <edumazet@google.com>, Jiri Pirko <jiri@resnulli.us>,
netdev@vger.kernel.org
Subject: Re: [PATCH net-next] net_sched: act_bpf: remove spinlock in fast path
Date: Tue, 04 Aug 2015 10:55:07 +0200 [thread overview]
Message-ID: <55C07DEB.1010902@iogearbox.net> (raw)
In-Reply-To: <1438664952-24712-1-git-send-email-ast@plumgrid.com>
On 08/04/2015 07:09 AM, Alexei Starovoitov wrote:
> Similar to act_gact/act_mirred, act_bpf can be lockless in packet processing.
>
> Also similar to gact/mirred there is a race between prog->filter and
> prog->tcf_action. Meaning that the program being replaced may use
> previous default action if it happened to return TC_ACT_UNSPEC.
> act_mirred race betwen tcf_action and tcfm_dev is similar.
> In all cases the race is harmless.
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?
> Long term we may want to improve the situation by replacing the whole
> struct tc_action as single pointer instead of updating inner fields one by one.
>
> Signed-off-by: Alexei Starovoitov <ast@plumgrid.com>
next prev parent reply other threads:[~2015-08-04 8:55 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-08-04 5:09 [PATCH net-next] net_sched: act_bpf: remove spinlock in fast path Alexei Starovoitov
2015-08-04 8:55 ` Daniel Borkmann [this message]
2015-08-04 16:35 ` Alexei Starovoitov
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