Messages in this thread Patch in this message | | | From | Qais Yousef <> | Subject | [PATCH 2/3] sched/fair: Fixes for capacity inversion detection | Date | Sun, 27 Nov 2022 14:17:41 +0000 |
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Traversing the Perf Domains requires rcu_read_lock() to be held and is conditional on sched_energy_enabled(). rcu_read_lock() is held while in load_balance(), add an assert to ensure this is always the case.
Also skip capacity inversion detection for our own pd; which was an error.
Fixes: 44c7b80bffc3 ("sched/fair: Detect capacity inversion") Reported-by: Dietmar Eggemann <dietmar.eggemann@arm.com> Signed-off-by: Qais Yousef (Google) <qyousef@layalina.io> --- kernel/sched/fair.c | 8 +++++++- 1 file changed, 7 insertions(+), 1 deletion(-)
diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c index 89dadaafc1ec..7c0dd57e562a 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -8856,16 +8856,22 @@ static void update_cpu_capacity(struct sched_domain *sd, int cpu) * * Thermal pressure will impact all cpus in this perf domain * equally. */ - if (static_branch_unlikely(&sched_asym_cpucapacity)) { + if (sched_energy_enabled()) { unsigned long inv_cap = capacity_orig - thermal_load_avg(rq); struct perf_domain *pd = rcu_dereference(rq->rd->pd); rq->cpu_capacity_inverted = 0; + SCHED_WARN_ON(!rcu_read_lock_held()); + for (; pd; pd = pd->next) { struct cpumask *pd_span = perf_domain_span(pd); unsigned long pd_cap_orig, pd_cap; + /* We can't be inverted against our own pd */ + if (cpumask_test_cpu(cpu_of(rq), pd_span)) + continue; + cpu = cpumask_any(pd_span); pd_cap_orig = arch_scale_cpu_capacity(cpu); -- 2.25.1
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