netdev - Re: [PATCH net-next 1/8] bpf: multi program support for cgroup+bpf

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Message-ID: <1211d4c0-b812-af08-cbd4-72eb9259ee78@cumulusnetworks.com>
Date:   Mon, 2 Oct 2017 21:26:36 -0700
From:   David Ahern <dsa@...ulusnetworks.com>
To:     Alexei Starovoitov <ast@...com>,
        "David S . Miller" <davem@...emloft.net>
Cc:     Daniel Borkmann <daniel@...earbox.net>, Tejun Heo <tj@...nel.org>,
        netdev@...r.kernel.org, kernel-team@...com
Subject: Re: [PATCH net-next 1/8] bpf: multi program support for cgroup+bpf

On 10/2/17 9:21 PM, Alexei Starovoitov wrote:
> 
> i'm not sure what you're trying to say.
> The first loop quoted above is inside cgroup_bpf_put()
> which is called when cgroup is destroyed. At this point
> we're detaching and prog_put all attached programs.
> While there is only one static_branch_inc() in __cgroup_bpf_attach()
> that is called every time the prog is attached to a cgroup.
> So what's the concern?

just asking if cgroup_bpf_enabled_key is 0 when all programs are removed
-- ie., that the inc's and dec's are equal. Reviewing this patch it was
not clear that they are.

> Note we're doing branch_dec only for progs in prog_list.
> Just like we do branch_inc only for progs in prog_list.
> Computing prog_array doesn't involve manipulations with prog's refcnt
> and no branch_inc/dec either.
>