From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S964901AbdKCAUF convert rfc822-to-8bit (ORCPT ); Thu, 2 Nov 2017 20:20:05 -0400 Received: from ozlabs.org ([103.22.144.67]:46767 "EHLO ozlabs.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932201AbdKCAUD (ORCPT ); Thu, 2 Nov 2017 20:20:03 -0400 From: Michael Ellerman To: Madhavan Srinivasan , Anju T Sudhakar Cc: linuxppc-dev@lists.ozlabs.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] powerpc/perf: Fix core-imc hotplug callback failure during imc initialization In-Reply-To: References: <1509443398-26539-1-git-send-email-anju@linux.vnet.ibm.com> <87efpi95wb.fsf@concordia.ellerman.id.au> Date: Fri, 03 Nov 2017 11:19:58 +1100 Message-ID: <87lgjo6wnl.fsf@concordia.ellerman.id.au> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 8BIT Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Madhavan Srinivasan writes: > On Wednesday 01 November 2017 06:22 AM, Michael Ellerman wrote: >> Anju T Sudhakar writes: >> >>> Call trace observed during boot: >> What's the actual oops? > > I could recreate this in mambo with CPUS=2 and THREAD=2 That boots fine for me. Presumably you've also done something to cause the CPU online to fail and trigger the bug. > Here is the complete stack trace. > > [    0.045367] core_imc memory allocation for cpu 2 failed > [    0.045408] Unable to handle kernel paging request for data at > address 0x7d20e2a6f92d03b8 > [    0.045443] Faulting instruction address: 0xc0000000000dde18 > cpu 0x0: Vector: 380 (Data Access Out of Range) at [c0000000fd1cb890] >     pc: c0000000000dde18: event_function_call+0x28/0x14c >     lr: c0000000000dde00: event_function_call+0x10/0x14c >     sp: c0000000fd1cbb10 >    msr: 9000000000009033 >    dar: 7d20e2a6f92d03b8 >   current = 0xc0000000fd15da00 >   paca    = 0xc00000000fff0000   softe: 0        irq_happened: 0x01 >     pid   = 11, comm = cpuhp/0 > Linux version 4.14.0-rc7-00014-g0a08377b127b (maddy@SrihariSrinidhi) > (gcc version 5.4.0 20160609 (Ubuntu/IBM 5.4.0-6ubuntu1~16.04.1)) #5 SMP > Wed Nov 1 14:12:27 IST 2017 > enter ? for help > [c0000000fd1cbb10] 0000000000000000 (unreliable) > [c0000000fd1cbba0] c0000000000de180 perf_remove_from_context+0x30/0x9c > [c0000000fd1cbbe0] c0000000000e9108 perf_pmu_migrate_context+0x9c/0x224 > [c0000000fd1cbc60] c0000000000682e0 ppc_core_imc_cpu_offline+0xdc/0x144 > [c0000000fd1cbcb0] c000000000070568 cpuhp_invoke_callback+0xe4/0x244 > [c0000000fd1cbd10] c000000000070824 cpuhp_thread_fun+0x15c/0x1b0 > [c0000000fd1cbd60] c00000000008e8cc smpboot_thread_fn+0x1e0/0x200 > [c0000000fd1cbdc0] c00000000008ae58 kthread+0x150/0x158 > [c0000000fd1cbe30] c00000000000b464 ret_from_kernel_thread+0x5c/0x78 > > >> >>> [c000000ff38ffb80] c0000000002ddfac perf_pmu_migrate_context+0xac/0x470 >>> [c000000ff38ffc40] c00000000011385c ppc_core_imc_cpu_offline+0x1ac/0x1e0 >>> [c000000ff38ffc90] c000000000125758 cpuhp_invoke_callback+0x198/0x5d0 >>> [c000000ff38ffd00] c00000000012782c cpuhp_thread_fun+0x8c/0x3d0 >>> [c000000ff38ffd60] c0000000001678d0 smpboot_thread_fn+0x290/0x2a0 >>> [c000000ff38ffdc0] c00000000015ee78 kthread+0x168/0x1b0 >>> [c000000ff38ffe30] c00000000000b368 ret_from_kernel_thread+0x5c/0x74 >>> >>> While registering the cpuhoplug callbacks for core-imc, if we fails >>> in the cpuhotplug online path for any random core (either because opal call to >>> initialize the core-imc counters fails or because memory allocation fails for >>> that core), ppc_core_imc_cpu_offline() will get invoked for other cpus who >>> successfully returned from cpuhotplug online path. >>> >>> But in the ppc_core_imc_cpu_offline() path we are trying to migrate the event >>> context, when core-imc counters are not even initialized. Thus creating the >>> above stack dump. >>> >>> Add a check to see if core-imc counters are enabled or not in the cpuhotplug >>> offline path before migrating the context to handle this failing scenario. >> Why do we need a bool to track this? Can't we just check the data >> structure we're deinitialising has been initialised? > > My bad. yes we could do that. Something like this will work? > > @@ -606,6 +608,20 @@ static int ppc_core_imc_cpu_offline(unsigned int cpu) >         if (!cpumask_test_and_clear_cpu(cpu, &core_imc_cpumask)) >                 return 0; > > +       /* > +        * Check whether core_imc is registered. We could end up here > +        * if the cpuhotplug callback registration fails. i.e, callback > +        * invokes the offline path for all sucessfully registered cpus. > +        * At this stage, core_imc pmu will not be registered and we > +        * should return here. > +        * > +        * We return with a zero since this is not a offline failure. > +        * And cpuhp_setup_state() returns the actual failure reason > +        * to the caller, which inturn will call the cleanup routine. > +        */ > +       if (!core_imc_pmu->pmu.event_init) > +               return 0; > + >         /* Find any online cpu in that core except the current "cpu" */ >         ncpu = cpumask_any_but(cpu_sibling_mask(cpu), cpu); That's not ideal, because you're grovelling into the details of the pmu struct. But I guess it's OK for now. cheers