For CONFIG_CPUMASK_OFFSTACK=y kernel, explicit allocation of cpumask variable on stack is not recommended since it can cause potential stack overflow. Instead, kernel code should always use *cpumask_var API(s) to allocate cpumask var in config-neutral way, leaving allocation strategy to CONFIG_CPUMASK_OFFSTACK. But dynamic allocation in cpuhp's teardown callback is somewhat problematic for if allocation fails(which is unlikely but still possible): - If -ENOMEM is returned to caller, kernel crashes for non-bringup teardown; - If callback pretends nothing happened and returns 0 to caller, it may trap system into an in-consisitent/compromised state; Use newly-introduced cpumask_any_and_but() to address all issues above. It eliminates usage of temporary cpumask var in generic way, no matter how the cpumask var is allocated. Suggested-by: Mark Rutland <mark.rutland@xxxxxxx> Signed-off-by: Dawei Li <dawei.li@xxxxxxxxxxxx> --- drivers/perf/alibaba_uncore_drw_pmu.c | 10 +++------- 1 file changed, 3 insertions(+), 7 deletions(-) diff --git a/drivers/perf/alibaba_uncore_drw_pmu.c b/drivers/perf/alibaba_uncore_drw_pmu.c index a9277dcf90ce..d4d14b65c4a5 100644 --- a/drivers/perf/alibaba_uncore_drw_pmu.c +++ b/drivers/perf/alibaba_uncore_drw_pmu.c @@ -746,18 +746,14 @@ static int ali_drw_pmu_offline_cpu(unsigned int cpu, struct hlist_node *node) struct ali_drw_pmu_irq *irq; struct ali_drw_pmu *drw_pmu; unsigned int target; - int ret; - cpumask_t node_online_cpus; irq = hlist_entry_safe(node, struct ali_drw_pmu_irq, node); if (cpu != irq->cpu) return 0; - ret = cpumask_and(&node_online_cpus, - cpumask_of_node(cpu_to_node(cpu)), cpu_online_mask); - if (ret) - target = cpumask_any_but(&node_online_cpus, cpu); - else + target = cpumask_any_and_but(cpumask_of_node(cpu_to_node(cpu)), + cpu_online_mask, cpu); + if (target >= nr_cpu_ids) target = cpumask_any_but(cpu_online_mask, cpu); if (target >= nr_cpu_ids) -- 2.27.0
