linux.git/kernel/sched/deadline.c, branch v5.10.258

sched/deadline: Use online cpus for validating runtime

2025-04-10T12:31:00+00:00

[ Upstream commit 14672f059d83f591afb2ee1fff56858efe055e5a ]

The ftrace selftest reported a failure because writing -1 to
sched_rt_runtime_us returns -EBUSY. This happens when the possible
CPUs are different from active CPUs.

Active CPUs are part of one root domain, while remaining CPUs are part
of def_root_domain. Since active cpumask is being used, this results in
cpus=0 when a non active CPUs is used in the loop.

Fix it by looping over the online CPUs instead for validating the
bandwidth calculations.

Signed-off-by: Shrikanth Hegde 
Signed-off-by: Ingo Molnar 
Reviewed-by: Juri Lelli 
Link: https://lore.kernel.org/r/20250306052954.452005-2-sshegde@linux.ibm.com
Signed-off-by: Sasha Levin

sched/deadline: Create DL BW alloc, free & check overflow interface

2023-08-30T14:23:18+00:00

commit 85989106feb734437e2d598b639991b9185a43a6 upstream.

While moving a set of tasks between exclusive cpusets,
cpuset_can_attach() -> task_can_attach() calls dl_cpu_busy(..., p) for
DL BW overflow checking and per-task DL BW allocation on the destination
root_domain for the DL tasks in this set.

This approach has the issue of not freeing already allocated DL BW in
the following error cases:

(1) The set of tasks includes multiple DL tasks and DL BW overflow
    checking fails for one of the subsequent DL tasks.

(2) Another controller next to the cpuset controller which is attached
    to the same cgroup fails in its can_attach().

To address this problem rework dl_cpu_busy():

(1) Split it into dl_bw_check_overflow() & dl_bw_alloc() and add a
    dedicated dl_bw_free().

(2) dl_bw_alloc() & dl_bw_free() take a `u64 dl_bw` parameter instead of
    a `struct task_struct *p` used in dl_cpu_busy(). This allows to
    allocate DL BW for a set of tasks too rather than only for a single
    task.

Signed-off-by: Dietmar Eggemann 
Signed-off-by: Juri Lelli 
Signed-off-by: Tejun Heo 
Signed-off-by: Qais Yousef (Google) 
Signed-off-by: Greg Kroah-Hartman

sched/cpuset: Keep track of SCHED_DEADLINE task in cpusets

2023-08-30T14:23:17+00:00

commit 6c24849f5515e4966d94fa5279bdff4acf2e9489 upstream.

Qais reported that iterating over all tasks when rebuilding root domains
for finding out which ones are DEADLINE and need their bandwidth
correctly restored on such root domains can be a costly operation (10+
ms delays on suspend-resume).

To fix the problem keep track of the number of DEADLINE tasks belonging
to each cpuset and then use this information (followup patch) to only
perform the above iteration if DEADLINE tasks are actually present in
the cpuset for which a corresponding root domain is being rebuilt.

Reported-by: Qais Yousef (Google) 
Link: https://lore.kernel.org/lkml/20230206221428.2125324-1-qyousef@layalina.io/
Signed-off-by: Juri Lelli 
Reviewed-by: Waiman Long 
Signed-off-by: Tejun Heo 
[ Fix conflicts in kernel/cgroup/cpuset.c and kernel/sched/deadline.c
  due to pulling new fields and functions. Remove new code and match the
  patch diff. ]
Signed-off-by: Qais Yousef (Google) 
Signed-off-by: Greg Kroah-Hartman

sched/deadline,rt: Remove unused parameter from pick_next_[rt|dl]_entity()

2023-03-11T15:39:15+00:00

[ Upstream commit 821aecd09e5ad2f8d4c3d8195333d272b392f7d3 ]

The `struct rq *rq` parameter isn't used. Remove it.

Signed-off-by: Dietmar Eggemann 
Signed-off-by: Peter Zijlstra (Intel) 
Acked-by: Juri Lelli 
Link: https://lore.kernel.org/r/20220302183433.333029-7-dietmar.eggemann@arm.com
Stable-dep-of: 7c4a5b89a0b5 ("sched/rt: pick_next_rt_entity(): check list_entry")
Signed-off-by: Sasha Levin

sched/deadline: Merge dl_task_can_attach() and dl_cpu_busy()

2022-08-21T13:16:12+00:00

[ Upstream commit 772b6539fdda31462cc08368e78df60b31a58bab ]

Both functions are doing almost the same, that is checking if admission
control is still respected.

With exclusive cpusets, dl_task_can_attach() checks if the destination
cpuset (i.e. its root domain) has enough CPU capacity to accommodate the
task.
dl_cpu_busy() checks if there is enough CPU capacity in the cpuset in
case the CPU is hot-plugged out.

dl_task_can_attach() is used to check if a task can be admitted while
dl_cpu_busy() is used to check if a CPU can be hotplugged out.

Make dl_cpu_busy() able to deal with a task and use it instead of
dl_task_can_attach() in task_can_attach().

Signed-off-by: Dietmar Eggemann 
Signed-off-by: Peter Zijlstra (Intel) 
Acked-by: Juri Lelli 
Link: https://lore.kernel.org/r/20220302183433.333029-4-dietmar.eggemann@arm.com
Signed-off-by: Sasha Levin

sched/deadline: Fix BUG_ON condition for deboosted tasks

2022-07-29T15:19:24+00:00

commit ddfc710395cccc61247348df9eb18ea50321cbed upstream.

Tasks the are being deboosted from SCHED_DEADLINE might enter
enqueue_task_dl() one last time and hit an erroneous BUG_ON condition:
since they are not boosted anymore, the if (is_dl_boosted()) branch is
not taken, but the else if (!dl_prio) is and inside this one we
BUG_ON(!is_dl_boosted), which is of course false (BUG_ON triggered)
otherwise we had entered the if branch above. Long story short, the
current condition doesn't make sense and always leads to triggering of a
BUG.

Fix this by only checking enqueue flags, properly: ENQUEUE_REPLENISH has
to be present, but additional flags are not a problem.

Fixes: 64be6f1f5f71 ("sched/deadline: Don't replenish from a !SCHED_DEADLINE entity")
Signed-off-by: Juri Lelli 
Signed-off-by: Peter Zijlstra (Intel) 
Cc: stable@vger.kernel.org
Link: https://lkml.kernel.org/r/20220714151908.533052-1-juri.lelli@redhat.com
Signed-off-by: Greg Kroah-Hartman

sched/deadline: Fix missing clock update in migrate_task_rq_dl()

2021-09-15T07:50:24+00:00

[ 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 
Signed-off-by: Dietmar Eggemann 
Signed-off-by: Peter Zijlstra (Intel) 
Reviewed-by: Daniel Bristot de Oliveira 
Acked-by: Juri Lelli 
Link: https://lore.kernel.org/r/20210804135925.3734605-1-dietmar.eggemann@arm.com
Signed-off-by: Sasha Levin

sched/deadline: Fix reset_on_fork reporting of DL tasks

2021-09-15T07:50:24+00:00

[ Upstream commit f95091536f78971b269ec321b057b8d630b0ad8a ]

It is possible for sched_getattr() to incorrectly report the state of
the reset_on_fork flag when called on a deadline task.

Indeed, if the flag was set on a deadline task using sched_setattr()
with flags (SCHED_FLAG_RESET_ON_FORK | SCHED_FLAG_KEEP_PARAMS), then
p->sched_reset_on_fork will be set, but __setscheduler() will bail out
early, which means that the dl_se->flags will not get updated by
__setscheduler_params()->__setparam_dl(). Consequently, if
sched_getattr() is then called on the task, __getparam_dl() will
override kattr.sched_flags with the now out-of-date copy in dl_se->flags
and report the stale value to userspace.

To fix this, make sure to only copy the flags that are relevant to
sched_deadline to and from the dl_se->flags field.

Signed-off-by: Quentin Perret 
Signed-off-by: Peter Zijlstra (Intel) 
Link: https://lore.kernel.org/r/20210727101103.2729607-2-qperret@google.com
Signed-off-by: Sasha Levin

sched/rt: Fix Deadline utilization tracking during policy change

2021-07-14T14:56:09+00:00

[ Upstream commit d7d607096ae6d378b4e92d49946d22739c047d4c ]

DL keeps track of the utilization on a per-rq basis with the structure
avg_dl. This utilization is updated during task_tick_dl(),
put_prev_task_dl() and set_next_task_dl(). However, when the current
running task changes its policy, set_next_task_dl() which would usually
take care of updating the utilization when the rq starts running DL
tasks, will not see a such change, leaving the avg_dl structure outdated.
When that very same task will be dequeued later, put_prev_task_dl() will
then update the utilization, based on a wrong last_update_time, leading to
a huge spike in the DL utilization signal.

The signal would eventually recover from this issue after few ms. Even
if no DL tasks are run, avg_dl is also updated in
__update_blocked_others(). But as the CPU capacity depends partly on the
avg_dl, this issue has nonetheless a significant impact on the scheduler.

Fix this issue by ensuring a load update when a running task changes
its policy to DL.

Fixes: 3727e0e ("sched/dl: Add dl_rq utilization tracking")
Signed-off-by: Vincent Donnefort 
Signed-off-by: Peter Zijlstra (Intel) 
Reviewed-by: Vincent Guittot 
Link: https://lore.kernel.org/r/1624271872-211872-3-git-send-email-vincent.donnefort@arm.com
Signed-off-by: Sasha Levin

sched/deadline: Fix sched_dl_global_validate()

2020-12-30T10:52:59+00:00

[ Upstream commit a57415f5d1e43c3a5c5d412cd85e2792d7ed9b11 ]

When change sched_rt_{runtime, period}_us, we validate that the new
settings should at least accommodate the currently allocated -dl
bandwidth:

  sched_rt_handler()
    -->	sched_dl_bandwidth_validate()
	{
		new_bw = global_rt_runtime()/global_rt_period();

		for_each_possible_cpu(cpu) {
			dl_b = dl_bw_of(cpu);
			if (new_bw < dl_b->total_bw)    <-------
				ret = -EBUSY;
		}
	}

But under CONFIG_SMP, dl_bw is per root domain , but not per CPU,
dl_b->total_bw is the allocated bandwidth of the whole root domain.
Instead, we should compare dl_b->total_bw against "cpus*new_bw",
where 'cpus' is the number of CPUs of the root domain.

Also, below annotation(in kernel/sched/sched.h) implied implementation
only appeared in SCHED_DEADLINE v2[1], then deadline scheduler kept
evolving till got merged(v9), but the annotation remains unchanged,
meaningless and misleading, update it.

* With respect to SMP, the bandwidth is given on a per-CPU basis,
* meaning that:
*  - dl_bw (< 100%) is the bandwidth of the system (group) on each CPU;
*  - dl_total_bw array contains, in the i-eth element, the currently
*    allocated bandwidth on the i-eth CPU.

[1]: https://lore.kernel.org/lkml/1267385230.13676.101.camel@Palantir/

Fixes: 332ac17ef5bf ("sched/deadline: Add bandwidth management for SCHED_DEADLINE tasks")
Signed-off-by: Peng Liu 
Signed-off-by: Peter Zijlstra (Intel) 
Reviewed-by: Daniel Bristot de Oliveira 
Acked-by: Juri Lelli 
Link: https://lkml.kernel.org/r/db6bbda316048cda7a1bbc9571defde193a8d67e.1602171061.git.iwtbavbm@gmail.com
Signed-off-by: Sasha Levin