linux-kernel - Re: [PATCH] cgroup: disable irqs while holding css_set

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Date:	Tue, 7 Jun 2016 11:14:02 +0100
From:	Juri Lelli <juri.lelli@....com>
To:	Daniel Bristot de Oliveira <bristot@...hat.com>
Cc:	linux-kernel@...r.kernel.org, Rik van Riel <riel@...hat.com>,
	"Luis Claudio R. Goncalves" <lgoncalv@...hat.com>,
	Tejun Heo <tj@...nel.org>, Li Zefan <lizefan@...wei.com>,
	Johannes Weiner <hannes@...xchg.org>, cgroups@...r.kernel.org
Subject: Re: [PATCH] cgroup: disable irqs while holding css_set_lock

Hi,

On 06/06/16 19:24, Daniel Bristot de Oliveira wrote:
> While testing the deadline scheduler + cgroup setup I hit this
> warning.
> 
> [  132.612935] ------------[ cut here ]------------
> [  132.612951] WARNING: CPU: 5 PID: 0 at kernel/softirq.c:150 __local_bh_enable_ip+0x6b/0x80
> [  132.612952] Modules linked in: (a ton of modules...)
> [  132.612981] CPU: 5 PID: 0 Comm: swapper/5 Not tainted 4.7.0-rc2 #2
> [  132.612981] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.8.2-20150714_191134- 04/01/2014
> [  132.612982]  0000000000000086 45c8bb5effdd088b ffff88013fd43da0 ffffffff813d229e
> [  132.612984]  0000000000000000 0000000000000000 ffff88013fd43de0 ffffffff810a652b
> [  132.612985]  00000096811387b5 0000000000000200 ffff8800bab29d80 ffff880034c54c00
> [  132.612986] Call Trace:
> [  132.612987]  <IRQ>  [<ffffffff813d229e>] dump_stack+0x63/0x85
> [  132.612994]  [<ffffffff810a652b>] __warn+0xcb/0xf0
> [  132.612997]  [<ffffffff810e76a0>] ? push_dl_task.part.32+0x170/0x170
> [  132.612999]  [<ffffffff810a665d>] warn_slowpath_null+0x1d/0x20
> [  132.613000]  [<ffffffff810aba5b>] __local_bh_enable_ip+0x6b/0x80
> [  132.613008]  [<ffffffff817d6c8a>] _raw_write_unlock_bh+0x1a/0x20
> [  132.613010]  [<ffffffff817d6c9e>] _raw_spin_unlock_bh+0xe/0x10
> [  132.613015]  [<ffffffff811388ac>] put_css_set+0x5c/0x60
> [  132.613016]  [<ffffffff8113dc7f>] cgroup_free+0x7f/0xa0
> [  132.613017]  [<ffffffff810a3912>] __put_task_struct+0x42/0x140
> [  132.613018]  [<ffffffff810e776a>] dl_task_timer+0xca/0x250
> [  132.613027]  [<ffffffff810e76a0>] ? push_dl_task.part.32+0x170/0x170
> [  132.613030]  [<ffffffff8111371e>] __hrtimer_run_queues+0xee/0x270
> [  132.613031]  [<ffffffff81113ec8>] hrtimer_interrupt+0xa8/0x190
> [  132.613034]  [<ffffffff81051a58>] local_apic_timer_interrupt+0x38/0x60
> [  132.613035]  [<ffffffff817d9b0d>] smp_apic_timer_interrupt+0x3d/0x50
> [  132.613037]  [<ffffffff817d7c5c>] apic_timer_interrupt+0x8c/0xa0
> [  132.613038]  <EOI>  [<ffffffff81063466>] ? native_safe_halt+0x6/0x10
> [  132.613043]  [<ffffffff81037a4e>] default_idle+0x1e/0xd0
> [  132.613044]  [<ffffffff810381cf>] arch_cpu_idle+0xf/0x20
> [  132.613046]  [<ffffffff810e8fda>] default_idle_call+0x2a/0x40
> [  132.613047]  [<ffffffff810e92d7>] cpu_startup_entry+0x2e7/0x340
> [  132.613048]  [<ffffffff81050235>] start_secondary+0x155/0x190
> [  132.613049] ---[ end trace f91934d162ce9977 ]---
> 
> The warn is the spin_(lock|unlock)_bh(&css_set_lock) in the interrupt
> context. Converting the spin_lock_bh to spin_lock_irqsave to avoid this
> problem - and other problems of sharing a spinlock with an interrupt.
> 

Interesting. And your test is using cpuset controller to partion
DEADLINE tasks and then modify groups concurrently?

Best,

- Juri