From: Kan Liang <kan.liang@xxxxxxxxxxxxxxx>
The below warning is triggered when building with arm
multi_v7_defconfig.
kernel/events/core.c: In function 'perf_event_setup_cpumask':
kernel/events/core.c:14012:13: warning: the comparison will always
evaluate as 'true' for the address of 'thread_sibling' will never be
NULL [-Waddress]
14012 | if (!topology_sibling_cpumask(cpu)) {
The perf_event_init_cpu() may be invoked at the early boot stage, while
the topology_*_cpumask hasn't been initialized yet. The check is to
specially handle the case, and initialize the perf_online_<domain>_masks
on the boot CPU.
X86 uses a per-cpu cpumask pointer, which could be NULL at the early
boot stage. However, ARM uses a global variable, which never be NULL.
Use perf_online_mask as an indicator instead. Only initialize the
perf_online_<domain>_masks when perf_online_mask is empty.
Fix a typo as well.
Fixes: 4ba4f1afb6a9 ("perf: Generic hotplug support for a PMU with a scope")
Reported-by: Stephen Rothwell <sfr@xxxxxxxxxxxxxxxx>
Closes: https://lore.kernel.org/lkml/20240911153854.240bbc1f@xxxxxxxxxxxxxxxx/
Reported-by: Steven Price <steven.price@xxxxxxx>
Closes: https://lore.kernel.org/lkml/1835eb6d-3e05-47f3-9eae-507ce165c3bf@xxxxxxx/
Signed-off-by: Kan Liang <kan.liang@xxxxxxxxxxxxxxx>
---
kernel/events/core.c | 10 +++++-----
1 file changed, 5 insertions(+), 5 deletions(-)
diff --git a/kernel/events/core.c b/kernel/events/core.c
index 7a028474caef..20e97c1aa4d6 100644
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -13954,21 +13954,19 @@ static void perf_event_setup_cpumask(unsigned int cpu)
struct cpumask *pmu_cpumask;
unsigned int scope;
- cpumask_set_cpu(cpu, perf_online_mask);
-
/*
* Early boot stage, the cpumask hasn't been set yet.
* The perf_online_<domain>_masks includes the first CPU of each domain.
- * Always uncondifionally set the boot CPU for the perf_online_<domain>_masks.
+ * Always unconditionally set the boot CPU for the perf_online_<domain>_masks.
*/
- if (!topology_sibling_cpumask(cpu)) {
+ if (cpumask_empty(perf_online_mask)) {
for (scope = PERF_PMU_SCOPE_NONE + 1; scope < PERF_PMU_MAX_SCOPE; scope++) {
pmu_cpumask = perf_scope_cpumask(scope);
if (WARN_ON_ONCE(!pmu_cpumask))
continue;
cpumask_set_cpu(cpu, pmu_cpumask);
}
- return;
+ goto end;
}
for (scope = PERF_PMU_SCOPE_NONE + 1; scope < PERF_PMU_MAX_SCOPE; scope++) {
@@ -13983,6 +13981,8 @@ static void perf_event_setup_cpumask(unsigned int cpu)
cpumask_any_and(pmu_cpumask, cpumask) >= nr_cpu_ids)
cpumask_set_cpu(cpu, pmu_cpumask);
}
+end:
+ cpumask_set_cpu(cpu, perf_online_mask);
}
int perf_event_init_cpu(unsigned int cpu)
--
2.38.1
