linux-kernel - Re: [PATCH v2 1/2] powerpc/powernv/cpuidle: Pass correct drv->cpumask for registration

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Date:   Mon, 27 Mar 2017 21:38:35 +1100
From:   Michael Ellerman <mpe@...erman.id.au>
To:     "Rafael J. Wysocki" <rafael@...nel.org>,
        Vaidyanathan Srinivasan <svaidy@...ux.vnet.ibm.com>
Cc:     Michael Neuling <mikey@...ling.org>,
        "Rafael J . Wysocki" <rjw@...ysocki.net>,
        Daniel Lezcano <daniel.lezcano@...aro.org>,
        linuxppc-dev <linuxppc-dev@...ts.ozlabs.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Linux PM <linux-pm@...r.kernel.org>
Subject: Re: [PATCH v2 1/2] powerpc/powernv/cpuidle: Pass correct drv->cpumask for registration

"Rafael J. Wysocki" <rafael@...nel.org> writes:

> On Thu, Mar 23, 2017 at 4:22 PM, Vaidyanathan Srinivasan
> <svaidy@...ux.vnet.ibm.com> wrote:
>> drv->cpumask defaults to cpu_possible_mask in __cpuidle_driver_init().
>> On PowerNV platform cpu_present could be less than cpu_possible in cases
>> where firmware detects the cpu, but it is not available to the OS.  When
>> CONFIG_HOTPLUG_CPU=n, such cpus are not hotplugable at runtime and hence
>> we skip creating cpu_device.
>>
>> This breaks cpuidle on powernv where register_cpu() is not called for
>> cpus in cpu_possible_mask that cannot be hot-added at runtime.
>>
>> Trying cpuidle_register_device() on cpu without cpu_device will cause
>> crash like this:
>>
>> cpu 0xf: Vector: 380 (Data SLB Access) at [c000000ff1503490]
>>     pc: c00000000022c8bc: string+0x34/0x60
>>     lr: c00000000022ed78: vsnprintf+0x284/0x42c
>>     sp: c000000ff1503710
>>    msr: 9000000000009033
>>    dar: 6000000060000000
>>   current = 0xc000000ff1480000
>>   paca    = 0xc00000000fe82d00   softe: 0        irq_happened: 0x01
>>     pid   = 1, comm = swapper/8
>> Linux version 4.11.0-rc2 (sv@...arika) (gcc version 4.9.4
>> (Buildroot 2017.02-00004-gc28573e) ) #15 SMP Fri Mar 17 19:32:02 IST 2017
>> enter ? for help
>> [link register   ] c00000000022ed78 vsnprintf+0x284/0x42c
>> [c000000ff1503710] c00000000022ebb8 vsnprintf+0xc4/0x42c (unreliable)
>> [c000000ff1503800] c00000000022ef40 vscnprintf+0x20/0x44
>> [c000000ff1503830] c0000000000ab61c vprintk_emit+0x94/0x2cc
>> [c000000ff15038a0] c0000000000acc9c vprintk_func+0x60/0x74
>> [c000000ff15038c0] c000000000619694 printk+0x38/0x4c
>> [c000000ff15038e0] c000000000224950 kobject_get+0x40/0x60
>> [c000000ff1503950] c00000000022507c kobject_add_internal+0x60/0x2c4
>> [c000000ff15039e0] c000000000225350 kobject_init_and_add+0x70/0x78
>> [c000000ff1503a60] c00000000053c288 cpuidle_add_sysfs+0x9c/0xe0
>> [c000000ff1503ae0] c00000000053aeac cpuidle_register_device+0xd4/0x12c
>> [c000000ff1503b30] c00000000053b108 cpuidle_register+0x98/0xcc
>> [c000000ff1503bc0] c00000000085eaf0 powernv_processor_idle_init+0x140/0x1e0
>> [c000000ff1503c60] c00000000000cd60 do_one_initcall+0xc0/0x15c
>> [c000000ff1503d20] c000000000833e84 kernel_init_freeable+0x1a0/0x25c
>> [c000000ff1503dc0] c00000000000d478 kernel_init+0x24/0x12c
>> [c000000ff1503e30] c00000000000b564 ret_from_kernel_thread+0x5c/0x78
>>
>> This patch fixes the bug by passing correct cpumask from
>> powernv-cpuidle driver.
>>
>> Signed-off-by: Vaidyanathan Srinivasan <svaidy@...ux.vnet.ibm.com>
>
> That needs to be ACKed by someone familiar with powernv.

Acked-by: Michael Ellerman <mpe@...erman.id.au>

cheers