From: Steven Rostedt <rostedt@goodmis.org>
To: Oleksandr Natalenko <oleksandr@natalenko.name>
Cc: "David S. Miller" <davem@davemloft.net>,
Sebastian Andrzej Siewior <bigeasy@linutronix.de>,
Thomas Gleixner <tglx@linutronix.de>,
Eric Dumazet <edumazet@google.com>,
Dave Jones <davej@codemonkey.org.uk>,
netdev@vger.kernel.org, linux-rt-users@vger.kernel.org,
linux-kernel@vger.kernel.org
Subject: Re: WARN_ON() in netconsole with PREEMPT_RT
Date: Sun, 11 Nov 2018 21:01:05 -0500 [thread overview]
Message-ID: <20181111210105.7f376c35@vmware.local.home> (raw)
In-Reply-To: <a23ae3a8501d5c996d7a9dd2f27dd5fa@natalenko.name>
On Sun, 11 Nov 2018 21:16:00 +0100
Oleksandr Natalenko <oleksandr@natalenko.name> wrote:
> > This is a v4.19.1-rt3-based kernel.
> >
> > The WARN_ON() is:
> >
> > 362 void netpoll_send_udp(struct netpoll *np, const char *msg, int len)
> > 363 {
> > …
> > 372 WARN_ON_ONCE(!irqs_disabled());
> > …
> >
> > If that matters, I have "threadirqs" passed to the kernel.
> >
> > Netconsole seems to work even after this warning. Is this OK/expected?
> >
> > Thanks.
>
> 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?
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.
-- Steve
next prev parent reply other threads:[~2018-11-12 2:01 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-11-11 19:13 WARN_ON() in netconsole with PREEMPT_RT Oleksandr Natalenko
2018-11-11 20:16 ` Oleksandr Natalenko
2018-11-12 2:01 ` Steven Rostedt [this message]
2018-11-24 19:15 ` Oleksandr Natalenko
2018-11-30 18:04 ` Sebastian Andrzej Siewior
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