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Miller" , Eric Dumazet , Paolo Abeni , Simon Horman , Amerigo Wang , netdev@vger.kernel.org, linux-kernel@vger.kernel.org, kernel-team@meta.com Subject: Re: [PATCH net] netpoll: guard __netpoll_send_skb() with RCU read lock Message-ID: <20250305-dancing-pretty-kestrel-b269df@leitao> References: <20250303-netpoll_rcu_v2-v1-1-6b34d8a01fa2@debian.org> <20250304174732.2a1f2cb5@kernel.org> <20250305-tamarin-of-amusing-luck-b9c84f@leitao> <580ce055-b710-4e97-8d91-1cfea7ec4881@lunn.ch> Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <580ce055-b710-4e97-8d91-1cfea7ec4881@lunn.ch> On Wed, Mar 05, 2025 at 05:09:14PM +0100, Andrew Lunn wrote: > On Wed, Mar 05, 2025 at 01:09:49AM -0800, Breno Leitao wrote: > > Hello Jakub, > > > > On Tue, Mar 04, 2025 at 05:47:32PM -0800, Jakub Kicinski wrote: > > > On Mon, 03 Mar 2025 03:44:12 -0800 Breno Leitao wrote: > > > > + guard(rcu)(); > > > > > > Scoped guards if you have to. > > > Preferably just lock/unlock like a normal person.. > > > > Sure, I thought that we would be moving to scoped guards all across the > > board, at least that was my reading for a similar patch I sent a while > > ago: > > > > https://lore.kernel.org/all/20250224123016.GA17456@noisy.programming.kicks-ass.net/ > > > > Anyway, in which case should I use scoped guard instead of just being > > like a normal person? > > https://www.kernel.org/doc/html/latest/process/maintainer-netdev.html > > Section 1.6.5: Using device-managed and cleanup.h constructs > > Netdev remains skeptical about promises of all “auto-cleanup” APIs, > including even devm_ helpers, historically. They are not the > preferred style of implementation, merely an acceptable one. > > Use of guard() is discouraged within any function longer than 20 > lines, scoped_guard() is considered more readable. Using normal > lock/unlock is still (weakly) preferred. > > Low level cleanup constructs (such as __free()) can be used when > building APIs and helpers, especially scoped iterators. However, > direct use of __free() within networking core and drivers is > discouraged. Similar guidance applies to declaring variables > mid-function. > > So you need to spend time to find out what each subsystems view is on > various APIs. That is clear. thanks for the heads-up! --breno