linux-kernel - Re: [RESEND PATCH v2] clocksource/arm_arch

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Message-ID: <15e4006c-2ec0-c572-55e0-acbb75625eb4@lca.pw>
Date:   Fri, 14 Dec 2018 10:05:08 -0500
From:   Qian Cai <cai@....pw>
To:     Thomas Gleixner <tglx@...utronix.de>,
        Peter Zijlstra <peterz@...radead.org>
Cc:     akpm@...ux-foundation.org, mark.rutland@....com,
        marc.zyngier@....com, daniel.lezcano@...aro.org, mingo@...nel.org,
        longman@...hat.com, linux-arm-kernel@...ts.infradead.org,
        linux-kernel@...r.kernel.org
Subject: Re: [RESEND PATCH v2] clocksource/arm_arch_timer: fix a lockdep
 warning



On 12/10/18 4:31 PM, Thomas Gleixner wrote:
> On Mon, 10 Dec 2018, Peter Zijlstra wrote:
>> On Mon, Dec 10, 2018 at 08:52:28AM -0500, Qian Cai wrote:
>>> Booting this Huawei TaiShan 2280 arm64 server generated this lockdep
>>> warning.
>>>
>>> [    0.000000]  lockdep_assert_cpus_held+0x50/0x60
>>> [    0.000000]  static_key_enable_cpuslocked+0x30/0xe8
>>> [    0.000000]  arch_timer_check_ool_workaround+0x128/0x2d0
>>> [    0.000000]  arch_timer_acpi_init+0x274/0x6ac
>>> [    0.000000]  acpi_table_parse+0x1ac/0x218
>>> [    0.000000]  __acpi_probe_device_table+0x164/0x1ec
>>> [    0.000000]  timer_probe+0x1bc/0x254
>>> [    0.000000]  time_init+0x44/0x98
>>> [    0.000000]  start_kernel+0x4ec/0x7d4
>>
>> It seems to me we want something like:
>>
>> ---
>>  kernel/cpu.c | 2 ++
>>  1 file changed, 2 insertions(+)
>>
>> diff --git a/kernel/cpu.c b/kernel/cpu.c
>> index 91d5c38eb7e5..e1ee8caf28b5 100644
>> --- a/kernel/cpu.c
>> +++ b/kernel/cpu.c
>> @@ -313,6 +313,8 @@ void cpus_write_unlock(void)
>>  
>>  void lockdep_assert_cpus_held(void)
>>  {
>> +	if (system_state < SYSTEM_RUNNING)
>> +		return;
>>  	percpu_rwsem_assert_held(&cpu_hotplug_lock);
>>  }
>  
> Hmm, no. SYSTEM_SCHEDULING is what you want because RUNNING is set way too
> late.

SYSTEM_SCHEDULING works well here too.