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sched/fair: Fixes for capacity inversion detection

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Traversing the Perf Domains requires rcu_read_lock() to be held and is
conditional on sched_energy_enabled(). Ensure right protections applied.

Also skip capacity inversion detection for our own pd; which was an
error.

Fixes: 44c7b80bff ("sched/fair: Detect capacity inversion")
Reported-by: Dietmar Eggemann <dietmar.eggemann@arm.com>
Signed-off-by: Qais Yousef (Google) <qyousef@layalina.io>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Vincent Guittot <vincent.guittot@linaro.org>
Link: https://lore.kernel.org/r/20230112122708.330667-3-qyousef@layalina.io
This commit is contained in:
Qais Yousef 2023-01-12 12:27:08 +00:00 committed by Peter Zijlstra
parent e26fd28db8
commit da07d2f9c1
1 changed files with 11 additions and 2 deletions
repo.diff.show_diff_stats Download patch file Download diff file Expand all files Collapse all files

13
kernel/sched/fair.c
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@ -8868,16 +8868,23 @@ 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);
struct perf_domain *pd;
rcu_read_lock();
pd = rcu_dereference(rq->rd->pd);
rq->cpu_capacity_inverted = 0;
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);
@ -8902,6 +8909,8 @@ static void update_cpu_capacity(struct sched_domain *sd, int cpu)
break;
}
}
rcu_read_unlock();
}
trace_sched_cpu_capacity_tp(rq);