A missing clock update is causing the following warning:
rq->clock_update_flags < RQCF_ACT_SKIP
WARNING: CPU: 112 PID: 2041 at kernel/sched/sched.h:1453
sub_running_bw.isra.0+0x190/0x1a0
...
CPU: 112 PID: 2041 Comm: sugov:112 Tainted: G W 5.14.0-rc1 #1
Hardware name: WIWYNN Mt.Jade Server System
B81.030Z1.0007/Mt.Jade Motherboard, BIOS 1.6.20210526 (SCP:
1.06.20210526) 2021/05/26
...
Call trace:
sub_running_bw.isra.0+0x190/0x1a0
migrate_task_rq_dl+0xf8/0x1e0
set_task_cpu+0xa8/0x1f0
try_to_wake_up+0x150/0x3d4
wake_up_q+0x64/0xc0
__up_write+0xd0/0x1c0
up_write+0x4c/0x2b0
cppc_set_perf+0x120/0x2d0
cppc_cpufreq_set_target+0xe0/0x1a4 [cppc_cpufreq]
__cpufreq_driver_target+0x74/0x140
sugov_work+0x64/0x80
kthread_worker_fn+0xe0/0x230
kthread+0x138/0x140
ret_from_fork+0x10/0x18
The task causing this is the `cppc_fie` DL task introduced by
commit 1eb5dde674 ("cpufreq: CPPC: Add support for frequency
invariance").
With CONFIG_ACPI_CPPC_CPUFREQ_FIE=y and schedutil cpufreq governor on
slow-switching system (like on this Ampere Altra WIWYNN Mt. Jade Arm
Server):
DL task `curr=sugov:112` lets `p=cppc_fie` migrate and since the latter
is in `non_contending` state, migrate_task_rq_dl() calls
sub_running_bw()->__sub_running_bw()->cpufreq_update_util()->
rq_clock()->assert_clock_updated()
on p.
Fix this by updating the clock for a non_contending task in
migrate_task_rq_dl() before calling sub_running_bw().
Reported-by: Bruno Goncalves <bgoncalv@redhat.com>
Signed-off-by: Dietmar Eggemann <dietmar.eggemann@arm.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Daniel Bristot de Oliveira <bristot@kernel.org>
Acked-by: Juri Lelli <juri.lelli@redhat.com>
Link: https://lore.kernel.org/r/20210804135925.3734605-1-dietmar.eggemann@arm.com
b4da13aa28