linux-kernel - Re: [PATCH] cpufreq: prevent 'policy->cpus' become offline in __gov_queue

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Date:	Wed, 5 Jun 2013 14:23:42 +0530
From:	Viresh Kumar <viresh.kumar@...aro.org>
To:	Michael Wang <wangyun@...ux.vnet.ibm.com>
Cc:	cpufreq@...r.kernel.org, linux-pm@...r.kernel.org,
	LKML <linux-kernel@...r.kernel.org>, rjw@...k.pl,
	Jiri Kosina <jkosina@...e.cz>, Borislav Petkov <bp@...en8.de>,
	Frederic Weisbecker <fweisbec@...il.com>,
	"tony.luck@...el.com" <tony.luck@...el.com>,
	Thomas Gleixner <tglx@...utronix.de>, x86@...nel.org,
	"paulmck@...ux.vnet.ibm.com" <paulmck@...ux.vnet.ibm.com>
Subject: Re: [PATCH] cpufreq: prevent 'policy->cpus' become offline in __gov_queue_work()

On 5 June 2013 14:19, Michael Wang <wangyun@...ux.vnet.ibm.com> wrote:
>
> Jiri Kosina <jkosina@...e.cz> and Borislav Petkov <bp@...en8.de>
> reported the warning:
>
> [   51.616759] ------------[ cut here ]------------
> [   51.621460] WARNING: at arch/x86/kernel/smp.c:123 native_smp_send_reschedule+0x58/0x60()
> [   51.629638] Modules linked in: ext2 vfat fat loop snd_hda_codec_hdmi usbhid snd_hda_codec_realtek coretemp kvm_intel kvm snd_hda_intel snd_hda_codec crc32_pclmul crc32c_intel ghash_clmulni_intel snd_hwdep snd_pcm aesni_intel sb_edac aes_x86_64 ehci_pci snd_page_alloc glue_helper snd_timer xhci_hcd snd iTCO_wdt iTCO_vendor_support ehci_hcd edac_core lpc_ich acpi_cpufreq lrw gf128mul ablk_helper cryptd mperf usbcore usb_common soundcore mfd_core dcdbas evdev pcspkr processor i2c_i801 button microcode
> [   51.675581] CPU: 0 PID: 244 Comm: kworker/1:1 Tainted: G        W    3.10.0-rc1+ #10
> [   51.683407] Hardware name: Dell Inc. Precision T3600/0PTTT9, BIOS A08 01/24/2013
> [   51.690901] Workqueue: events od_dbs_timer
> [   51.695069]  0000000000000009 ffff88043a2f5b68 ffffffff8161441c ffff88043a2f5ba8
> [   51.702602]  ffffffff8103e540 0000000000000033 0000000000000001 ffff88043d5f8000
> [   51.710136]  00000000ffff0ce1 0000000000000001 ffff88044fc4fc08 ffff88043a2f5bb8
> [   51.717691] Call Trace:
> [   51.720191]  [<ffffffff8161441c>] dump_stack+0x19/0x1b
> [   51.725396]  [<ffffffff8103e540>] warn_slowpath_common+0x70/0xa0
> [   51.731473]  [<ffffffff8103e58a>] warn_slowpath_null+0x1a/0x20
> [   51.737378]  [<ffffffff81025628>] native_smp_send_reschedule+0x58/0x60
> [   51.744013]  [<ffffffff81072cfd>] wake_up_nohz_cpu+0x2d/0xa0
> [   51.749745]  [<ffffffff8104f6bf>] add_timer_on+0x8f/0x110
> [   51.755214]  [<ffffffff8105f6fe>] __queue_delayed_work+0x16e/0x1a0
> [   51.761470]  [<ffffffff8105f251>] ? try_to_grab_pending+0xd1/0x1a0
> [   51.767724]  [<ffffffff8105f78a>] mod_delayed_work_on+0x5a/0xa0
> [   51.773719]  [<ffffffff814f6b5d>] gov_queue_work+0x4d/0xc0
> [   51.779271]  [<ffffffff814f60cb>] od_dbs_timer+0xcb/0x170
> [   51.784734]  [<ffffffff8105e75d>] process_one_work+0x1fd/0x540
> [   51.790634]  [<ffffffff8105e6f2>] ? process_one_work+0x192/0x540
> [   51.796711]  [<ffffffff8105ef22>] worker_thread+0x122/0x380
> [   51.802350]  [<ffffffff8105ee00>] ? rescuer_thread+0x320/0x320
> [   51.808264]  [<ffffffff8106634a>] kthread+0xea/0xf0
> [   51.813200]  [<ffffffff81066260>] ? flush_kthread_worker+0x150/0x150
> [   51.819644]  [<ffffffff81623d5c>] ret_from_fork+0x7c/0xb0
> [   51.918165] nouveau E[     DRM] GPU lockup - switching to software fbcon
> [   51.930505]  [<ffffffff81066260>] ? flush_kthread_worker+0x150/0x150
> [   51.936994] ---[ end trace f419538ada83b5c5 ]---
>
> It was caused by the policy->cpus changed during the process of
> __gov_queue_work(), in other word, cpu offline happened.
>
> This patch will use get/put_online_cpus() to prevent the offline
> happen inside __gov_queue_work(), after applied the patch, the
> warning is gone as Jiri tested:
>
>         Link: https://lkml.org/lkml/2013/6/5/88
>
> CC: "Rafael J. Wysocki" <rjw@...k.pl>
> CC: Viresh Kumar <viresh.kumar@...aro.org>
> Reported-by: Borislav Petkov <bp@...en8.de>
> Reported-by: Jiri Kosina <jkosina@...e.cz>
> Tested-by: Jiri Kosina <jkosina@...e.cz>
> Signed-off-by: Michael Wang <wangyun@...ux.vnet.ibm.com>
> ---
>  drivers/cpufreq/cpufreq_governor.c |    3 +++
>  1 files changed, 3 insertions(+), 0 deletions(-)

Acked-by: Viresh Kumar <viresh.kumar@...aro.org>
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