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    Subject[PATCH 5.13 008/300] sched/deadline: Fix missing clock update in migrate_task_rq_dl()
    Date
    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;
    /*
    --
    2.30.2


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