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perf: Fix topology_sibling_cpumask check warning on ARM

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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: 4ba4f1afb6 ("perf: Generic hotplug support for a PMU with a scope")
Reported-by: Stephen Rothwell <sfr@canb.auug.org.au>
Closes: https://lore.kernel.org/lkml/20240911153854.240bbc1f@canb.auug.org.au/
Reported-by: Steven Price <steven.price@arm.com>
Closes: https://lore.kernel.org/lkml/1835eb6d-3e05-47f3-9eae-507ce165c3bf@arm.com/
Signed-off-by: Kan Liang <kan.liang@linux.intel.com>
Tested-by: Steven Price <steven.price@arm.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Kan Liang 2024-09-12 07:50:25 -07:00 committed by Linus Torvalds
parent 88264981f2
commit 673a5009cf
1 changed files with 5 additions and 5 deletions
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10
kernel/events/core.c
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@ -14002,21 +14002,19 @@ 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++) {
@ -14031,6 +14029,8 @@ 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)