This is a note to let you know that I've just added the patch titled
sched/fair: Fixes for capacity inversion detection
to the 5.15-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
sched-fair-fixes-for-capacity-inversion-detection.patch
and it can be found in the queue-5.15 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From stable-owner@xxxxxxxxxxxxxxx Tue Apr 18 16:06:11 2023
From: Qais Yousef <qyousef@xxxxxxxxxxx>
Date: Tue, 18 Apr 2023 15:05:47 +0100
Subject: sched/fair: Fixes for capacity inversion detection
To: stable@xxxxxxxxxxxxxxx, Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>, Vincent Guittot <vincent.guittot@xxxxxxxxxx>, Dietmar Eggemann <dietmar.eggemann@xxxxxxx>, Qais Yousef <qyousef@xxxxxxxxxxx>
Message-ID: <20230418140547.88035-8-qyousef@xxxxxxxxxxx>
From: Qais Yousef <qyousef@xxxxxxxxxxx>
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@xxxxxxx>
Signed-off-by: Qais Yousef (Google) <qyousef@xxxxxxxxxxx>
Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
Reviewed-by: Vincent Guittot <vincent.guittot@xxxxxxxxxx>
Link: https://lore.kernel.org/r/20230112122708.330667-3-qyousef@xxxxxxxxxxx
(cherry picked from commit da07d2f9c153e457e845d4dcfdd13568d71d18a4)
Signed-off-by: Qais Yousef (Google) <qyousef@xxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
kernel/sched/fair.c | 13 +++++++++++--
1 file changed, 11 insertions(+), 2 deletions(-)
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -8649,16 +8649,23 @@ 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);
@@ -8683,6 +8690,8 @@ static void update_cpu_capacity(struct s
break;
}
}
+
+ rcu_read_unlock();
}
trace_sched_cpu_capacity_tp(rq);
Patches currently in stable-queue which might be from stable-owner@xxxxxxxxxxxxxxx are
queue-5.15/sched-fair-detect-capacity-inversion.patch
queue-5.15/sched-uclamp-make-cpu_overutilized-use-util_fits_cpu.patch
queue-5.15/sched-uclamp-fix-fits_capacity-check-in-feec.patch
queue-5.15/sched-fair-consider-capacity-inversion-in-util_fits_cpu.patch
queue-5.15/sched-fair-fixes-for-capacity-inversion-detection.patch
queue-5.15/sched-uclamp-fix-a-uninitialized-variable-warnings.patch
queue-5.15/sched-uclamp-cater-for-uclamp-in-find_energy_efficient_cpu-s-early-exit-condition.patch
