From: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
To: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
Cc: peterz@infradead.org, mingo@redhat.com,
linux-kernel@vger.kernel.org, tglx@linutronix.de
Subject: Re: native_smp_send_reschedule() splat from rt_mutex_lock()?
Date: Wed, 20 Sep 2017 18:24:47 +0200 [thread overview]
Message-ID: <20170920162447.5j5kcs3t6kzbilql@linutronix.de> (raw)
In-Reply-To: <20170918165110.GA9975@linux.vnet.ibm.com>
On 2017-09-18 09:51:10 [-0700], Paul E. McKenney wrote:
> Hello!
Hi,
> [11072.586518] sched: Unexpected reschedule of offline CPU#6!
> [11072.587578] ------------[ cut here ]------------
> [11072.588563] WARNING: CPU: 0 PID: 59 at /home/paulmck/public_git/linux-rcu/arch/x86/kernel/smp.c:128 native_smp_send_reschedule+0x37/0x40
> [11072.591543] Modules linked in:
> [11072.591543] CPU: 0 PID: 59 Comm: rcub/10 Not tainted 4.14.0-rc1+ #1
> [11072.610596] Call Trace:
> [11072.611531] resched_curr+0x61/0xd0
> [11072.611531] switched_to_rt+0x8f/0xa0
> [11072.612647] rt_mutex_setprio+0x25c/0x410
> [11072.613591] task_blocks_on_rt_mutex+0x1b3/0x1f0
> [11072.614601] rt_mutex_slowlock+0xa9/0x1e0
> [11072.615567] rt_mutex_lock+0x29/0x30
> [11072.615567] rcu_boost_kthread+0x127/0x3c0
> In theory, I could work around this by excluding CPU-hotplug operations
> while doing RCU priority boosting, but in practice I am very much hoping
> that there is a more reasonable solution out there...
so in CPUHP_TEARDOWN_CPU / take_cpu_down() / __cpu_disable() the CPU is
marked as offline and interrupt handling is disabled. Later in
CPUHP_AP_SCHED_STARTING / sched_cpu_dying() all tasks are migrated away.
Did this hit a random task during a CPU-hotplug operation which was not
yet migrated away from the dying CPU? In theory a futex_unlock() of a RT
task could also produce such a backtrace.
> Thanx, Paul
>
Sebastian
next prev parent reply other threads:[~2017-09-20 16:24 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-09-18 16:51 Paul E. McKenney
2017-09-20 16:24 ` Sebastian Andrzej Siewior [this message]
2017-09-20 19:44 ` Paul E. McKenney
2017-09-21 12:41 ` Peter Zijlstra
2017-09-21 13:28 ` Sebastian Andrzej Siewior
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