linux-kernel - Re: [PATCH] [RESEND] x86/smpboot: avoid warning messages while hot-removing physical cpu

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Message-ID: <8e5fa962-bc68-822b-3028-cff36c2a14fd@gmail.com>
Date:   Wed, 7 Feb 2018 07:36:42 -0500
From:   Masayoshi Mizuma <msys.mizuma@...il.com>
To:     yasu.isimatu@...il.com, tglx@...utronix.de, mingo@...hat.com,
        hpa@...or.com, x86@...nel.org
Cc:     linux-kernel@...r.kernel.org, ak@...ux.intel.com
Subject: Re: [PATCH] [RESEND] x86/smpboot: avoid warning messages while
 hot-removing physical cpu

Hello Yasuaki,

Thank you for your comment.
I will add the Fixes tag and resend the patch.

- Masayoshi

Wed, 7 Feb 2018 19:24:26 +0900 Yasuaki Ishimatsu wrote:
> CC:+Andi Kleen
> 
> Hi Masayoshi,
> 
> This issue is caused by the following commit:
> 
> commit 30bb9811856f667042e746d8033883b1091a46ce
> Author: Andi Kleen <ak@...ux.intel.com>
> Date:   Tue Nov 14 07:42:56 2017 -0500
> 
>     x86/topology: Avoid wasting 128k for package id array
> 
> So you should add the following "Fixes:" tag in the description.
> 
> Fixes: 30bb9811856f ("x86/topology: Avoid wasting 128k for package id array")
> 
> Thanks,
> Yasuaki Ishimatsu
> 
> On 02/05/2018 10:51 PM, Masayoshi Mizuma wrote:
>> From: Masayoshi Mizuma <m.mizuma@...fujitsu.com>
>>
>> When a physical cpu is hot-removed, the following warning message
>> are shown while the uncore device is removing in uncore_pci_remove().
>>
>> WARNING: CPU: 120 PID: 5 at arch/x86/events/intel/uncore.c:988
>> uncore_pci_remove+0xf1/0x110
>> ...
>> CPU: 120 PID: 5 Comm: kworker/u1024:0 Not tainted 4.15.0-rc8 #1
>> Workqueue: kacpi_hotplug acpi_hotplug_work_fn
>> ...
>> Call Trace:
>> pci_device_remove+0x36/0xb0
>> device_release_driver_internal+0x145/0x210
>> pci_stop_bus_device+0x76/0xa0
>> pci_stop_root_bus+0x44/0x60
>> acpi_pci_root_remove+0x1f/0x80
>> acpi_bus_trim+0x54/0x90
>> acpi_bus_trim+0x2e/0x90
>> acpi_device_hotplug+0x2bc/0x4b0
>> acpi_hotplug_work_fn+0x1a/0x30
>> process_one_work+0x141/0x340
>> worker_thread+0x47/0x3e0
>> kthread+0xf5/0x130
>>
>> When uncore_pci_remove() runs, it tries to get package id to
>> clear the value of uncore_extra_pci_dev[].dev[] by using
>> topology_phys_to_logical_pkg(). The warning messesage are
>> shown because topology_phys_to_logical_pkg() returns -1.
>>
>>   arch/x86/events/intel/uncore.c:
>>   static void uncore_pci_remove(struct pci_dev *pdev)
>>   {
>>   ...
>>           phys_id = uncore_pcibus_to_physid(pdev->bus);
>>   ...
>>                   pkg = topology_phys_to_logical_pkg(phys_id); //returns -1
>>                   for (i = 0; i < UNCORE_EXTRA_PCI_DEV_MAX; i++) {
>>                           if (uncore_extra_pci_dev[pkg].dev[i] == pdev) {
>>                                   uncore_extra_pci_dev[pkg].dev[i] = NULL;
>>                                   break;
>>                           }
>>                   }
>>                   WARN_ON_ONCE(i >= UNCORE_EXTRA_PCI_DEV_MAX); //HERE!!
>>
>> topology_phys_to_logical_pkg() tries to find
>> cpuinfo_x86->phys_proc_id that matches the phys_pkg argument.
>>
>>   arch/x86/kernel/smpboot.c:
>>   int topology_phys_to_logical_pkg(unsigned int phys_pkg)
>>   {
>>           int cpu;
>>   
>>           for_each_possible_cpu(cpu) {
>>                   struct cpuinfo_x86 *c = &cpu_data(cpu);
>>   
>>                   if (c->initialized && c->phys_proc_id == phys_pkg)
>>                           return c->logical_proc_id;
>>           }
>>           return -1;
>>   }
>>
>> However, the phys_proc_id is already set to 0 by remove_siblinginfo()
>> when the cpu was offlined.
>> So, topology_phys_to_logical_pkg() cannot find correct the
>> logical_proc_id and always returns -1.
>> As the result, uncore_pci_remove() calls WARN_ON_ONCE() and the warning
>> messages are shown.
>>
>> To avoid this, remove the setting from remove_siblinginfo().
>> There is no influence about the removing because phys_proc_id is not
>> used after it is hot-removed and it is re-set while hot-addeding.
>>
>> Signed-off-by: Masayoshi Mizuma <m.mizuma@...fujitsu.com>
>>  
>> ---
>>  arch/x86/kernel/smpboot.c | 1 -
>>  1 file changed, 1 deletion(-)
>>
>> diff --git a/arch/x86/kernel/smpboot.c b/arch/x86/kernel/smpboot.c
>> index ed556d5..844279c 100644
>> --- a/arch/x86/kernel/smpboot.c
>> +++ b/arch/x86/kernel/smpboot.c
>> @@ -1431,7 +1431,6 @@ static void remove_siblinginfo(int cpu)
>>  	cpumask_clear(cpu_llc_shared_mask(cpu));
>>  	cpumask_clear(topology_sibling_cpumask(cpu));
>>  	cpumask_clear(topology_core_cpumask(cpu));
>> -	c->phys_proc_id = 0;
>>  	c->cpu_core_id = 0;
>>  	cpumask_clear_cpu(cpu, cpu_sibling_setup_mask);
>>  	recompute_smt_state();
>>