From 0b167f11085a34281349f395d200052b61a7e221 Mon Sep 17 00:00:00 2001 From: "Guilherme G. Piccoli" Date: Thu, 19 Oct 2017 17:41:33 -0200 Subject: [PATCH] powerpc/perf: Fix IMC allocation routine When setting nr_cpus=1, we observed a crash in IMC code during boot due to a missing allocation: basically, IMC code is taking the number of threads into account in imc_mem_init() and if we manually set nr_cpus for a value that is not multiple of the number of threads per core, an integer division in that function will discard the decimal portion, leading IMC to not allocate one mem_info struct. This causes a NULL pointer dereference later, on is_core_imc_mem_inited(). This patch just rounds that division up, fixing the bug. Signed-off-by: Guilherme G. Piccoli Acked-by: Anju T Sudhakar Signed-off-by: Michael Ellerman --- arch/powerpc/perf/imc-pmu.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/arch/powerpc/perf/imc-pmu.c b/arch/powerpc/perf/imc-pmu.c index 88126245881b..92ae5de0bbac 100644 --- a/arch/powerpc/perf/imc-pmu.c +++ b/arch/powerpc/perf/imc-pmu.c @@ -1104,7 +1104,7 @@ static int init_nest_pmu_ref(void) static void cleanup_all_core_imc_memory(void) { - int i, nr_cores = num_present_cpus() / threads_per_core; + int i, nr_cores = DIV_ROUND_UP(num_present_cpus(), threads_per_core); struct imc_mem_info *ptr = core_imc_pmu->mem_info; int size = core_imc_pmu->counter_mem_size; @@ -1212,7 +1212,7 @@ static int imc_mem_init(struct imc_pmu *pmu_ptr, struct device_node *parent, if (!pmu_ptr->pmu.name) return -ENOMEM; - nr_cores = num_present_cpus() / threads_per_core; + nr_cores = DIV_ROUND_UP(num_present_cpus(), threads_per_core); pmu_ptr->mem_info = kcalloc(nr_cores, sizeof(struct imc_mem_info), GFP_KERNEL); -- 2.20.1