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Miller" , Eric Dumazet , Jakub Kicinski , Paolo Abeni , Simon Horman , Clark Williams , Steven Rostedt , Stephen Hemminger , Arend van Spriel , linux-kernel@vger.kernel.org, linux-rt-devel@lists.linux.dev Subject: Re: [PATCH net v2 1/2] netpoll: use a raw lock for the deferred transmit queue Message-ID: References: <20260928064239.32456-1-kmehltretter@gmail.com> <20260930192103.62973-2-kmehltretter@gmail.com> <20261001074819.gQ3w8q6P@linutronix.de> <20261009155225.6Uy7b0wd@linutronix.de> X-Mailing-List: netdev@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20261009155225.6Uy7b0wd@linutronix.de> Hello Sebastian, On Fri, Oct 09, 2026 at 05:52:25PM +0200, Sebastian Andrzej Siewior wrote: > I would suggest to untangle that local-irq-disable assumption. Then we > end up with the ::write_atomic callback on PREEMPT_RT which will raise > warnings. But those will appear only on panic() and as the last console > due to CON_NBCON_ATOMIC_UNSAFE so everything will go according to the > plan. > On !RT the whole __netpoll_send_skb() will be with disabled interrupts > due to the console lock. On RT it won't and I don't know if anything > down the call chain assumes that. Thanks for the patch, On PREEMPT_RT, the send path is clean. all the selftest I have are passing fine, without a single splat, while the unpatched kernel produces about a dozen over the same tests. On !RT, the first message triggers, but it doesn't seem a big deal. WARNING: kernel/softirq.c:453 at __local_bh_enable_ip+0x118/0x120, CPU#4: pr/netcons_netc/307 ... Call trace: __local_bh_enable_ip+0x118/0x120 (P) netpoll_send_skb+0x1a8/0x364 send_udp+0x348/0x4a8 netconsole_write+0x16c/0x628 nbcon_emit_next_record+0x150/0x3cc nbcon_emit_one+0x74/0x158 nbcon_kthread_func+0x18c/0x258 kthread+0x108/0x134 Anyway, is this patch something you are planning to send officially? Thanks, --breno