From: Qais Yousef qyousef@layalina.io
commit da07d2f9c153e457e845d4dcfdd13568d71d18a4 upstream.
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: 44c7b80bffc3 ("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 (cherry picked from commit da07d2f9c153e457e845d4dcfdd13568d71d18a4) Signed-off-by: Qais Yousef (Google) qyousef@layalina.io Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- kernel/sched/fair.c | 13 +++++++++++-- 1 file changed, 11 insertions(+), 2 deletions(-)
--- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -8407,16 +8407,23 @@ static void update_cpu_capacity(struct s * * 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);
@@ -8441,6 +8448,8 @@ static void update_cpu_capacity(struct s break; } } + + rcu_read_unlock(); }
trace_sched_cpu_capacity_tp(rq);