From: Dietmar Eggemann dietmar.eggemann@arm.com
[ Upstream commit b4da13aa28d4fd0071247b7b41c579ee8a86c81a ]
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 1eb5dde674f5 ("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 Signed-off-by: Sasha Levin sashal@kernel.org --- kernel/sched/deadline.c | 1 + 1 file changed, 1 insertion(+)
diff --git a/kernel/sched/deadline.c b/kernel/sched/deadline.c index 7ddb1202794f..fa29a69e14c9 100644 --- a/kernel/sched/deadline.c +++ b/kernel/sched/deadline.c @@ -1733,6 +1733,7 @@ static void migrate_task_rq_dl(struct task_struct *p, int new_cpu __maybe_unused */ raw_spin_lock(&rq->lock); if (p->dl.dl_non_contending) { + update_rq_clock(rq); sub_running_bw(&p->dl, &rq->dl); p->dl.dl_non_contending = 0; /*