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Miller" , Eric Dumazet , Jakub Kicinski , Paolo Abeni , Simon Horman , netdev@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH net-next] rtnetlink: comment the RCU and SRCU waits in unregister paths Date: Tue, 13 Oct 2026 12:52:58 +0200 Message-ID: <20261013105301.9037-1-parri.andrea@gmail.com> X-Mailer: git-send-email 2.53.0 In-Reply-To: References: <20261008124423.11543-1-parri.andrea@gmail.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit On Mon, Oct 12, 2026 at 06:48:22PM -0700, Kuniyuki Iwashima wrote: > > + /* Wait for rtnl_get_link() callers under RCU that may still > > + * dereference tab. > > + */ > > synchronize_net(); > > More specifically, this only applies to callers before try_module_get(). Right, the later lookup in rtnetlink_rcv_msg() runs under RTNL. I'll name rtnetlink_rcv_msg() and try_module_get() in v2. > > + /* Wait for rtnl_link_ops_get() callers to call rtnl_link_ops_put(). */ > > synchronize_srcu(&ops->srcu); > > I think we don't need comment for srcu as the relation is > clear via the argument. Agreed, I'll drop both srcu comments. > > + /* Wait for RCU walkers of rtnl_af_ops, including rtnl_af_lookup() > > + * readers that found ops but have not yet taken ops->srcu. > > + */ > > this can be simply /* see rtnl_link_unregister() */ instead of duplicating > comments. The two waits cover different readers, though. Besides rtnl_af_lookup(), the synchronize_rcu() in rtnl_af_unregister() also waits for the RCU walkers of rtnl_af_ops that invoke callbacks without ops->srcu: rtnl_link_get_af_size(), rtnl_fill_link_af() and the IFLA_STATS_AF_SPEC paths. link_ops has no analogous RCU-only list walkers, so a pointer there would miss them. I'd prefer to keep a local comment, reworded in v2 to mention those walkers. Thanks, Andrea