| Message ID | 20240403125109.2054881-10-dawei.li@shingroup.cn (mailing list archive) |
|---|---|
| State | Not Applicable |
| Headers | show |
| Series | perf: Avoid placing cpumask var on stack | expand |
On Wed, Apr 03, 2024 at 08:51:08PM +0800, Dawei Li wrote: > 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@arm.com> > Signed-off-by: Dawei Li <dawei.li@shingroup.cn> The logic looks good to me, but I'd like the commit message updated the same as per my comment on patch 2. With that commit message: Reviewed-by: Mark Rutland <mark.rutland@arm.com> Mark. > --- > drivers/perf/qcom_l2_pmu.c | 8 +++----- > 1 file changed, 3 insertions(+), 5 deletions(-) > > diff --git a/drivers/perf/qcom_l2_pmu.c b/drivers/perf/qcom_l2_pmu.c > index 148df5ae8ef8..b5a44dc1dc3a 100644 > --- a/drivers/perf/qcom_l2_pmu.c > +++ b/drivers/perf/qcom_l2_pmu.c > @@ -801,9 +801,8 @@ static int l2cache_pmu_online_cpu(unsigned int cpu, struct hlist_node *node) > > static int l2cache_pmu_offline_cpu(unsigned int cpu, struct hlist_node *node) > { > - struct cluster_pmu *cluster; > struct l2cache_pmu *l2cache_pmu; > - cpumask_t cluster_online_cpus; > + struct cluster_pmu *cluster; > unsigned int target; > > l2cache_pmu = hlist_entry_safe(node, struct l2cache_pmu, node); > @@ -820,9 +819,8 @@ static int l2cache_pmu_offline_cpu(unsigned int cpu, struct hlist_node *node) > cluster->on_cpu = -1; > > /* Any other CPU for this cluster which is still online */ > - cpumask_and(&cluster_online_cpus, &cluster->cluster_cpus, > - cpu_online_mask); > - target = cpumask_any_but(&cluster_online_cpus, cpu); > + target = cpumask_any_and_but(&cluster->cluster_cpus, > + cpu_online_mask, cpu); > if (target >= nr_cpu_ids) { > disable_irq(cluster->irq); > return 0; > -- > 2.27.0 >
diff --git a/drivers/perf/qcom_l2_pmu.c b/drivers/perf/qcom_l2_pmu.c index 148df5ae8ef8..b5a44dc1dc3a 100644 --- a/drivers/perf/qcom_l2_pmu.c +++ b/drivers/perf/qcom_l2_pmu.c @@ -801,9 +801,8 @@ static int l2cache_pmu_online_cpu(unsigned int cpu, struct hlist_node *node) static int l2cache_pmu_offline_cpu(unsigned int cpu, struct hlist_node *node) { - struct cluster_pmu *cluster; struct l2cache_pmu *l2cache_pmu; - cpumask_t cluster_online_cpus; + struct cluster_pmu *cluster; unsigned int target; l2cache_pmu = hlist_entry_safe(node, struct l2cache_pmu, node); @@ -820,9 +819,8 @@ static int l2cache_pmu_offline_cpu(unsigned int cpu, struct hlist_node *node) cluster->on_cpu = -1; /* Any other CPU for this cluster which is still online */ - cpumask_and(&cluster_online_cpus, &cluster->cluster_cpus, - cpu_online_mask); - target = cpumask_any_but(&cluster_online_cpus, cpu); + target = cpumask_any_and_but(&cluster->cluster_cpus, + cpu_online_mask, cpu); if (target >= nr_cpu_ids) { disable_irq(cluster->irq); return 0;
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@arm.com> Signed-off-by: Dawei Li <dawei.li@shingroup.cn> --- drivers/perf/qcom_l2_pmu.c | 8 +++----- 1 file changed, 3 insertions(+), 5 deletions(-)