Message ID | 20240403125109.2054881-6-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 08:51:04PM +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/arm_dsu_pmu.c | 19 ++++++------------- > 1 file changed, 6 insertions(+), 13 deletions(-) > > diff --git a/drivers/perf/arm_dsu_pmu.c b/drivers/perf/arm_dsu_pmu.c > index bae3ca37f846..adc0bbb5fafe 100644 > --- a/drivers/perf/arm_dsu_pmu.c > +++ b/drivers/perf/arm_dsu_pmu.c > @@ -230,15 +230,6 @@ static const struct attribute_group *dsu_pmu_attr_groups[] = { > NULL, > }; > > -static int dsu_pmu_get_online_cpu_any_but(struct dsu_pmu *dsu_pmu, int cpu) > -{ > - struct cpumask online_supported; > - > - cpumask_and(&online_supported, > - &dsu_pmu->associated_cpus, cpu_online_mask); > - return cpumask_any_but(&online_supported, cpu); > -} > - > static inline bool dsu_pmu_counter_valid(struct dsu_pmu *dsu_pmu, u32 idx) > { > return (idx < dsu_pmu->num_counters) || > @@ -827,14 +818,16 @@ static int dsu_pmu_cpu_online(unsigned int cpu, struct hlist_node *node) > > static int dsu_pmu_cpu_teardown(unsigned int cpu, struct hlist_node *node) > { > - int dst; > - struct dsu_pmu *dsu_pmu = hlist_entry_safe(node, struct dsu_pmu, > - cpuhp_node); > + struct dsu_pmu *dsu_pmu; > + unsigned int dst; > + > + dsu_pmu = hlist_entry_safe(node, struct dsu_pmu, cpuhp_node); > > if (!cpumask_test_and_clear_cpu(cpu, &dsu_pmu->active_cpu)) > return 0; > > - dst = dsu_pmu_get_online_cpu_any_but(dsu_pmu, cpu); > + dst = cpumask_any_and_but(&dsu_pmu->associated_cpus, > + cpu_online_mask, cpu); > /* If there are no active CPUs in the DSU, leave IRQ disabled */ > if (dst >= nr_cpu_ids) > return 0; > -- > 2.27.0 >
diff --git a/drivers/perf/arm_dsu_pmu.c b/drivers/perf/arm_dsu_pmu.c index bae3ca37f846..adc0bbb5fafe 100644 --- a/drivers/perf/arm_dsu_pmu.c +++ b/drivers/perf/arm_dsu_pmu.c @@ -230,15 +230,6 @@ static const struct attribute_group *dsu_pmu_attr_groups[] = { NULL, }; -static int dsu_pmu_get_online_cpu_any_but(struct dsu_pmu *dsu_pmu, int cpu) -{ - struct cpumask online_supported; - - cpumask_and(&online_supported, - &dsu_pmu->associated_cpus, cpu_online_mask); - return cpumask_any_but(&online_supported, cpu); -} - static inline bool dsu_pmu_counter_valid(struct dsu_pmu *dsu_pmu, u32 idx) { return (idx < dsu_pmu->num_counters) || @@ -827,14 +818,16 @@ static int dsu_pmu_cpu_online(unsigned int cpu, struct hlist_node *node) static int dsu_pmu_cpu_teardown(unsigned int cpu, struct hlist_node *node) { - int dst; - struct dsu_pmu *dsu_pmu = hlist_entry_safe(node, struct dsu_pmu, - cpuhp_node); + struct dsu_pmu *dsu_pmu; + unsigned int dst; + + dsu_pmu = hlist_entry_safe(node, struct dsu_pmu, cpuhp_node); if (!cpumask_test_and_clear_cpu(cpu, &dsu_pmu->active_cpu)) return 0; - dst = dsu_pmu_get_online_cpu_any_but(dsu_pmu, cpu); + dst = cpumask_any_and_but(&dsu_pmu->associated_cpus, + cpu_online_mask, cpu); /* If there are no active CPUs in the DSU, leave IRQ disabled */ if (dst >= nr_cpu_ids) 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/arm_dsu_pmu.c | 19 ++++++------------- 1 file changed, 6 insertions(+), 13 deletions(-)