From: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
To: Udo van den Heuvel <udovdh@xs4all.nl>
Cc: RT <linux-rt-users@vger.kernel.org>
Subject: Re: rcu_preempt detected stalls [5.9.1-rt]
Date: Thu, 18 Feb 2021 15:41:04 +0100 [thread overview]
Message-ID: <20210218144104.rfpcpzp6rhvks5vj@linutronix.de> (raw)
In-Reply-To: <47623850-fb85-aac0-9d44-85d7914a321f@xs4all.nl>
On 2021-01-31 10:13:30 [+0100], Udo van den Heuvel wrote:
> Hello,
Hi,
> Found these loggings in journal, what happened here?
09:20:24 RCU stalled on CPU0.
09:21:08 Networking was not able to send packets.
The RCU part indicates that something is blocking the CPU. The network
part might be related (it is not bound to a CPU but if the IRQ-thread is
blocked then packets won't be sent/acked).
09:21:19 systemd's watchdog killed tor because it was not responding.
Most of tor's threads were waiting in pthread_cond_wait().
One thread was in getsockopt(sock, SOL_TCP, TCP_INFO, ,,). This could
block/sleep in lock_sock_fast() but shouldn't since all threads were
idle. Unless a packet would be received at that time. tor does not
changes its priority so everything should run at SCHED_OTHER.
tor got killed in the end and you did not attach any more rcu warnings
so it appears that CPU0 is no longer blocked. I don't know what blocked
the CPU for the time.
> Kind regards,
> Udo
Sebastian
next prev parent reply other threads:[~2021-02-18 15:56 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-01-31 9:13 rcu_preempt detected stalls [5.9.1-rt] Udo van den Heuvel
2021-02-18 14:41 ` Sebastian Andrzej Siewior [this message]
2021-02-18 14:43 ` Sebastian Andrzej Siewior
2021-02-18 14:47 ` Udo van den Heuvel
2021-02-18 14:56 ` Sebastian Andrzej Siewior
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