From mboxrd@z Thu Jan 1 00:00:00 1970 From: Oleksandr Natalenko Subject: Re: WARN_ON() in netconsole with PREEMPT_RT Date: Sat, 24 Nov 2018 20:15:45 +0100 Message-ID: References: <20181111210105.7f376c35@vmware.local.home> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII; format=flowed Content-Transfer-Encoding: 7bit Cc: "David S. Miller" , Sebastian Andrzej Siewior , Thomas Gleixner , Eric Dumazet , Dave Jones , netdev@vger.kernel.org, linux-rt-users@vger.kernel.org, linux-kernel@vger.kernel.org, Nikolay Aleksandrov To: Steven Rostedt Return-path: In-Reply-To: <20181111210105.7f376c35@vmware.local.home> Sender: netdev-owner@vger.kernel.org List-Id: linux-rt-users.vger.kernel.org Hi. On 12.11.2018 03:01, Steven Rostedt wrote: > On Sun, 11 Nov 2018 21:16:00 +0100 > Oleksandr Natalenko wrote: >> Oh, I see that write_msg() calls netpoll_send_udp() under >> spin_lock_irqsave(), but in PREEMPT_RT this, AFAIK, does not disable >> interrupts. >> >> So, the real question here is whether the interrupts should be indeed >> disabled. And if so, -rt should replace spin_lock_irqsave() call there >> with what? local_irq_save()? and get rid of the warning? >> > > Why do we care if interrupts are disabled with PREEMPT_RT here? I don't know, if you ask me. But the check was added intentionally with c9fd56b34efd0, so the author had definitely something on his mind. Cc'ing him. > printk() itself has a lot of issues with PREEMPT_RT that we are working > on dealing with. Right now netconsole is actually at the end of that > todo list. OK, I see. -- Oleksandr Natalenko (post-factum)