netdev - Re: [PATCH net-next] net: sched: always disable bh when taking tcf

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Message-Id: <20180819.105100.1954465468537272629.davem@davemloft.net>
Date:   Sun, 19 Aug 2018 10:51:00 -0700 (PDT)
From:   David Miller <davem@...emloft.net>
To:     vladbu@...lanox.com
Cc:     netdev@...r.kernel.org, jhs@...atatu.com, xiyou.wangcong@...il.com,
        jiri@...nulli.us, ast@...nel.org, daniel@...earbox.net
Subject: Re: [PATCH net-next] net: sched: always disable bh when taking
 tcf_lock

From: Vlad Buslov <vladbu@...lanox.com>
Date: Tue, 14 Aug 2018 21:46:16 +0300

> Recently, ops->init() and ops->dump() of all actions were modified to
> always obtain tcf_lock when accessing private action state. Actions that
> don't depend on tcf_lock for synchronization with their data path use
> non-bh locking API. However, tcf_lock is also used to protect rate
> estimator stats in softirq context by timer callback.
> 
> Change ops->init() and ops->dump() of all actions to disable bh when using
> tcf_lock to prevent deadlock reported by following lockdep warning:
 ...
> Taking tcf_lock in sample action with bh disabled causes lockdep to issue a
> warning regarding possible irq lock inversion dependency between tcf_lock,
> and psample_groups_lock that is taken when holding tcf_lock in sample init:
 ...
> In order to prevent potential lock inversion dependency between tcf_lock
> and psample_groups_lock, extract call to psample_group_get() from tcf_lock
> protected section in sample action init function.
> 
> Fixes: 4e232818bd32 ("net: sched: act_mirred: remove dependency on rtnl lock")
> Fixes: 764e9a24480f ("net: sched: act_vlan: remove dependency on rtnl lock")
> Fixes: 729e01260989 ("net: sched: act_tunnel_key: remove dependency on rtnl lock")
> Fixes: d77284956656 ("net: sched: act_sample: remove dependency on rtnl lock")
> Fixes: e8917f437006 ("net: sched: act_gact: remove dependency on rtnl lock")
> Fixes: b6a2b971c0b0 ("net: sched: act_csum: remove dependency on rtnl lock")
> Fixes: 2142236b4584 ("net: sched: act_bpf: remove dependency on rtnl lock")
> Signed-off-by: Vlad Buslov <vladbu@...lanox.com>

Applied, thanks Vlad.