Message ID | 20221208145409.453308-1-qyousef@layalina.io (mailing list archive) |
---|---|
State | Handled Elsewhere, archived |
Headers | show |
Series | [v2] sched/fair: Fixes for capacity inversion detection | expand |
On 12/08/22 14:54, Qais Yousef wrote: > 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. Err that should say instead Traversing the Perf Domains requires rcu_read_lock() to be held and is conditional on sched_energy_enabled(). Ensure right protections applied. Peter, let me know if you want me to resend with that fixed or happy to apply yourself. Thanks! -- Qais Yousef > > 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> > --- > > Changes in v2: > > * Make sure to hold rcu_read_lock() as we need it's not held in all > paths (thanks Dietmar!)
diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c index 6a2fc2ca5078..2b1442093bd6 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -8856,16 +8856,23 @@ 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); @@ -8890,6 +8897,8 @@ static void update_cpu_capacity(struct sched_domain *sd, int cpu) break; } } + + rcu_read_unlock(); } trace_sched_cpu_capacity_tp(rq);
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> --- Changes in v2: * Make sure to hold rcu_read_lock() as we need it's not held in all paths (thanks Dietmar!) kernel/sched/fair.c | 13 +++++++++++-- 1 file changed, 11 insertions(+), 2 deletions(-)