From 673a5009cf2f020dac440cd79e70c4c8b8e20d08 Mon Sep 17 00:00:00 2001 From: Kan Liang Date: Thu, 12 Sep 2024 07:50:25 -0700 Subject: [PATCH] perf: Fix topology_sibling_cpumask check warning on ARM 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__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__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 Closes: https://lore.kernel.org/lkml/20240911153854.240bbc1f@canb.auug.org.au/ Reported-by: Steven Price Closes: https://lore.kernel.org/lkml/1835eb6d-3e05-47f3-9eae-507ce165c3bf@arm.com/ Signed-off-by: Kan Liang Tested-by: Steven Price Signed-off-by: Linus Torvalds --- 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 0016f5ff9ba2..5afde9f7b52a 100644 --- a/kernel/events/core.c +++ b/kernel/events/core.c @@ -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__masks includes the first CPU of each domain. - * Always uncondifionally set the boot CPU for the perf_online__masks. + * Always unconditionally set the boot CPU for the perf_online__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)