netdev - Re: [ovs-dev] [PATCH net-next v4 08/15] openvswitch: Use nested-BH locking for ovs_pcpu

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Message-ID: <f7t8qmze0um.fsf@redhat.com>
Date: Wed, 14 May 2025 10:14:09 -0400
From: Aaron Conole <aconole@...hat.com>
To: Sebastian Andrzej Siewior <bigeasy@...utronix.de>
Cc: netdev@...r.kernel.org,  linux-rt-devel@...ts.linux.dev,
  dev@...nvswitch.org,  Ilya Maximets <i.maximets@....org>,  Eric Dumazet
 <edumazet@...gle.com>,  Simon Horman <horms@...nel.org>,  Jakub Kicinski
 <kuba@...nel.org>,  Thomas Gleixner <tglx@...utronix.de>,  Paolo Abeni
 <pabeni@...hat.com>,  "David S. Miller" <davem@...emloft.net>
Subject: Re: [ovs-dev] [PATCH net-next v4 08/15] openvswitch: Use nested-BH
 locking for ovs_pcpu_storage

Sebastian Andrzej Siewior <bigeasy@...utronix.de> writes:

> ovs_pcpu_storage is a per-CPU variable and relies on disabled BH for its
> locking. Without per-CPU locking in local_bh_disable() on PREEMPT_RT
> this data structure requires explicit locking.
> The data structure can be referenced recursive and there is a recursion
> counter to avoid too many recursions.
>
> Add a local_lock_t to the data structure and use
> local_lock_nested_bh() for locking. Add an owner of the struct which is
> the current task and acquire the lock only if the structure is not owned
> by the current task.
>
> Cc: Aaron Conole <aconole@...hat.com>
> Cc: Eelco Chaudron <echaudro@...hat.com>
> Cc: Ilya Maximets <i.maximets@....org>
> Cc: dev@...nvswitch.org
> Signed-off-by: Sebastian Andrzej Siewior <bigeasy@...utronix.de>
> ---

Reviewed-by: Aaron Conole <aconole@...hat.com>