Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18;
Date:   Mon, 16 Aug 2021 08:47:41 -0700
From:   Jakub Kicinski <kuba@kernel.org>
To:     Leon Romanovsky <leon@kernel.org>
Cc:     "David S . Miller" <davem@davemloft.net>,
        Leon Romanovsky <leonro@nvidia.com>,
        Guangbin Huang <huangguangbin2@huawei.com>,
        Jacob Keller <jacob.e.keller@intel.com>,
        Jiri Pirko <jiri@nvidia.com>, linux-kernel@vger.kernel.org,
        netdev@vger.kernel.org, Salil Mehta <salil.mehta@huawei.com>,
        Shannon Nelson <snelson@pensando.io>,
        Yisen Zhuang <yisen.zhuang@huawei.com>,
        Yufeng Mo <moyufeng@huawei.com>
Subject: Re: [PATCH net-next 3/6] devlink: Count struct devlink consumers
Message-ID: <20210816084741.1dd1c415@kicinski-fedora-pc1c0hjn.dhcp.thefacebook.com>
In-Reply-To: <d4d59d801f4521e562c9ecf2d8767077aaefb456.1628933864.git.leonro@nvidia.com>
References: <cover.1628933864.git.leonro@nvidia.com>
        <d4d59d801f4521e562c9ecf2d8767077aaefb456.1628933864.git.leonro@nvidia.com>
MIME-Version: 1.0
Content-Type: text/plain; charset=US-ASCII
Content-Transfer-Encoding: 7bit
Precedence: bulk

On Sat, 14 Aug 2021 12:57:28 +0300 Leon Romanovsky wrote:
> From: Leon Romanovsky <leonro@nvidia.com>
> 
> The struct devlink itself is protected by internal lock and doesn't
> need global lock during operation. That global lock is used to protect
> addition/removal new devlink instances from the global list in use by
> all devlink consumers in the system.
> 
> The future conversion of linked list to be xarray will allow us to
> actually delete that lock, but first we need to count all struct devlink
> users.

Not a problem with this set but to state the obvious the global devlink
lock also protects from concurrent execution of all the ops which don't
take the instance lock (DEVLINK_NL_FLAG_NO_LOCK). You most likely know
this but I thought I'd comment on an off chance it helps.

> The reference counting provides us a way to ensure that no new user
> space commands success to grab devlink instance which is going to be
> destroyed makes it is safe to access it without lock.