Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S965049AbdCWP2e (ORCPT ); Thu, 23 Mar 2017 11:28:34 -0400 Received: from mail-oi0-f67.google.com ([209.85.218.67]:33330 "EHLO mail-oi0-f67.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S964903AbdCWP2d (ORCPT ); Thu, 23 Mar 2017 11:28:33 -0400 MIME-Version: 1.0 In-Reply-To: <20170323152247.14733-2-svaidy@linux.vnet.ibm.com> References: <20170323152247.14733-1-svaidy@linux.vnet.ibm.com> <20170323152247.14733-2-svaidy@linux.vnet.ibm.com> From: "Rafael J. Wysocki" Date: Thu, 23 Mar 2017 16:28:31 +0100 X-Google-Sender-Auth: vrOooW3GmNigjZ6ze_85vapWWGw Message-ID: Subject: Re: [PATCH v2 1/2] powerpc/powernv/cpuidle: Pass correct drv->cpumask for registration To: Vaidyanathan Srinivasan Cc: Michael Neuling , Michael Ellerman , "Rafael J . Wysocki" , Daniel Lezcano , linuxppc-dev , Linux Kernel Mailing List , Linux PM Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3888 Lines: 87 On Thu, Mar 23, 2017 at 4:22 PM, Vaidyanathan Srinivasan 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@sagarika) (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 That needs to be ACKed by someone familiar with powernv. > --- > drivers/cpuidle/cpuidle-powernv.c | 18 ++++++++++++++++++ > 1 file changed, 18 insertions(+) > > diff --git a/drivers/cpuidle/cpuidle-powernv.c b/drivers/cpuidle/cpuidle-powernv.c > index a06df51..82f7b33 100644 > --- a/drivers/cpuidle/cpuidle-powernv.c > +++ b/drivers/cpuidle/cpuidle-powernv.c > @@ -175,6 +175,24 @@ static int powernv_cpuidle_driver_init(void) > drv->state_count += 1; > } > > + /* > + * On PowerNV platform cpu_present may be less that cpu_possible in > + * cases where firmware detects the cpu, but it is not available to the > + * OS. If CONFIG_HOTPLUG_CPU=n then such CPUs are not hotplugable at > + * runtime and hence cpu_devices are not created for those cpus by > + * generic topology_init(). > + * > + * drv->cpumask defaults to cpu_possible_mask in > + * __cpuidle_driver_init(). This breaks cpuidle on powernv where > + * cpu_devices are not created for cpus in cpu_possible_mask that > + * cannot be hot-added later at runtime. > + * > + * Trying cpuidle_register_device() on a cpu without cpu_devices is > + * incorrect. Hence pass correct cpu mask to generic cpuidle driver. > + */ > + > + drv->cpumask = (struct cpumask *)cpu_present_mask; > + > return 0; > } > > -- > 2.9.3 >