Messages in this thread Patch in this message | | | From | Anju T Sudhakar <> | Subject | [PATCH] powerpc/perf: Fix core-imc hotplug callback failure during imc initialization | Date | Tue, 31 Oct 2017 15:19:58 +0530 |
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Call trace observed during boot:
[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.
Signed-off-by: Anju T Sudhakar <anju@linux.vnet.ibm.com> --- arch/powerpc/perf/imc-pmu.c | 15 +++++++++++++++ 1 file changed, 15 insertions(+)
diff --git a/arch/powerpc/perf/imc-pmu.c b/arch/powerpc/perf/imc-pmu.c index 8812624..08139f9 100644 --- a/arch/powerpc/perf/imc-pmu.c +++ b/arch/powerpc/perf/imc-pmu.c @@ -30,6 +30,7 @@ static struct imc_pmu *per_nest_pmu_arr[IMC_MAX_PMUS]; static cpumask_t nest_imc_cpumask; struct imc_pmu_ref *nest_imc_refc; static int nest_pmus; +static bool core_imc_enabled; /* Core IMC data structures and variables */ @@ -607,6 +608,19 @@ static int ppc_core_imc_cpu_offline(unsigned int cpu) if (!cpumask_test_and_clear_cpu(cpu, &core_imc_cpumask)) return 0; + /* + * See if core imc counters are enabled or not. + * + * Suppose we reach here from core_imc_cpumask_init(), + * since we failed at the cpuhotplug online path for any random + * core (either because opal call to initialize the core-imc counters + * failed or because memory allocation failed). + * We need to check whether core imc counters are enabled or not before + * migrating the event context from cpus in the other cores. + */ + if (!core_imc_enabled) + return 0; + /* Find any online cpu in that core except the current "cpu" */ ncpu = cpumask_any_but(cpu_sibling_mask(cpu), cpu); @@ -1299,6 +1313,7 @@ int init_imc_pmu(struct device_node *parent, struct imc_pmu *pmu_ptr, int pmu_id return ret; } + core_imc_enabled = true; break; case IMC_DOMAIN_THREAD: ret = thread_imc_cpu_init(); -- 2.7.4
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