sched: Restructure sched_class order sanity checks in sched_init()

Currently, sched_init() checks that the sched_class'es are in the expected
order by testing each adjacency which is a bit brittle a

sched: Restructure sched_class order sanity checks in sched_init()

Currently, sched_init() checks that the sched_class'es are in the expected
order by testing each adjacency which is a bit brittle and makes it
cumbersome to add optional sched_class'es. Instead, let's verify whether
they're in the expected order using sched_class_above() which is what
matters.

Signed-off-by: Tejun Heo <tj@kernel.org>
Suggested-by: Peter Zijlstra <peterz@infradead.org>
Reviewed-by: David Vernet <dvernet@meta.com>

show more ...

Merge tag 'sched-core-2024-09-19' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

Pull scheduler updates from Ingo Molnar:

- Implement the SCHED_DEADLINE server infrastructure - Daniel Br

Merge tag 'sched-core-2024-09-19' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

Pull scheduler updates from Ingo Molnar:

- Implement the SCHED_DEADLINE server infrastructure - Daniel Bristot
de Oliveira's last major contribution to the kernel:

"SCHED_DEADLINE servers can help fixing starvation issues of low
priority tasks (e.g., SCHED_OTHER) when higher priority tasks
monopolize CPU cycles. Today we have RT Throttling; DEADLINE
servers should be able to replace and improve that."

(Daniel Bristot de Oliveira, Peter Zijlstra, Joel Fernandes, Youssef
Esmat, Huang Shijie)

- Preparatory changes for sched_ext integration:
- Use set_next_task(.first) where required
- Fix up set_next_task() implementations
- Clean up DL server vs. core sched
- Split up put_prev_task_balance()
- Rework pick_next_task()
- Combine the last put_prev_task() and the first set_next_task()
- Rework dl_server
- Add put_prev_task(.next)

(Peter Zijlstra, with a fix by Tejun Heo)

- Complete the EEVDF transition and refine EEVDF scheduling:
- Implement delayed dequeue
- Allow shorter slices to wakeup-preempt
- Use sched_attr::sched_runtime to set request/slice suggestion
- Document the new feature flags
- Remove unused and duplicate-functionality fields
- Simplify & unify pick_next_task_fair()
- Misc debuggability enhancements

(Peter Zijlstra, with fixes/cleanups by Dietmar Eggemann, Valentin
Schneider and Chuyi Zhou)

- Initialize the vruntime of a new task when it is first enqueued,
resulting in significant decrease in latency of newly woken tasks
(Zhang Qiao)

- Introduce SM_IDLE and an idle re-entry fast-path in __schedule()
(K Prateek Nayak, Peter Zijlstra)

- Clean up and clarify the usage of Clean up usage of rt_task()
(Qais Yousef)

- Preempt SCHED_IDLE entities in strict cgroup hierarchies
(Tianchen Ding)

- Clarify the documentation of time units for deadline scheduler
parameters (Christian Loehle)

- Remove the HZ_BW chicken-bit feature flag introduced a year ago,
the original change seems to be working fine (Phil Auld)

- Misc fixes and cleanups (Chen Yu, Dan Carpenter, Huang Shijie,
Peilin He, Qais Yousefm and Vincent Guittot)

* tag 'sched-core-2024-09-19' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (64 commits)
sched/cpufreq: Use NSEC_PER_MSEC for deadline task
cpufreq/cppc: Use NSEC_PER_MSEC for deadline task
sched/deadline: Clarify nanoseconds in uapi
sched/deadline: Convert schedtool example to chrt
sched/debug: Fix the runnable tasks output
sched: Fix sched_delayed vs sched_core
kernel/sched: Fix util_est accounting for DELAY_DEQUEUE
kthread: Fix task state in kthread worker if being frozen
sched/pelt: Use rq_clock_task() for hw_pressure
sched/fair: Move effective_cpu_util() and effective_cpu_util() in fair.c
sched/core: Introduce SM_IDLE and an idle re-entry fast-path in __schedule()
sched: Add put_prev_task(.next)
sched: Rework dl_server
sched: Combine the last put_prev_task() and the first set_next_task()
sched: Rework pick_next_task()
sched: Split up put_prev_task_balance()
sched: Clean up DL server vs core sched
sched: Fixup set_next_task() implementations
sched: Use set_next_task(.first) where required
sched/fair: Properly deactivate sched_delayed task upon class change
...

show more ...

sched: Fix sched_delayed vs sched_core

Completely analogous to commit dfa0a574cbc4 ("sched/uclamg: Handle
delayed dequeue"), avoid double dequeue for the sched_core entries.

Fixes: 152e11f6df29 ("s

sched: Fix sched_delayed vs sched_core

Completely analogous to commit dfa0a574cbc4 ("sched/uclamg: Handle
delayed dequeue"), avoid double dequeue for the sched_core entries.

Fixes: 152e11f6df29 ("sched/fair: Implement delayed dequeue")
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>

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sched/core: Introduce SM_IDLE and an idle re-entry fast-path in __schedule()

Since commit b2a02fc43a1f ("smp: Optimize
send_call_function_single_ipi()") an idle CPU in TIF_POLLING_NRFLAG mode
can be

sched/core: Introduce SM_IDLE and an idle re-entry fast-path in __schedule()

Since commit b2a02fc43a1f ("smp: Optimize
send_call_function_single_ipi()") an idle CPU in TIF_POLLING_NRFLAG mode
can be pulled out of idle by setting TIF_NEED_RESCHED flag to service an
IPI without actually sending an interrupt. Even in cases where the IPI
handler does not queue a task on the idle CPU, do_idle() will call
__schedule() since need_resched() returns true in these cases.

Introduce and use SM_IDLE to identify call to __schedule() from
schedule_idle() and shorten the idle re-entry time by skipping
pick_next_task() when nr_running is 0 and the previous task is the idle
task.

With the SM_IDLE fast-path, the time taken to complete a fixed set of
IPIs using ipistorm improves noticeably. Following are the numbers
from a dual socket Intel Ice Lake Xeon server (2 x 32C/64T) and
3rd Generation AMD EPYC system (2 x 64C/128T) (boost on, C2 disabled)
running ipistorm between CPU8 and CPU16:

cmdline: insmod ipistorm.ko numipi=100000 single=1 offset=8 cpulist=8 wait=1

==================================================================
Test : ipistorm (modified)
Units : Normalized runtime
Interpretation: Lower is better
Statistic : AMean
======================= Intel Ice Lake Xeon ======================
kernel: time [pct imp]
tip:sched/core 1.00 [baseline]
tip:sched/core + SM_IDLE 0.80 [20.51%]
==================== 3rd Generation AMD EPYC =====================
kernel: time [pct imp]
tip:sched/core 1.00 [baseline]
tip:sched/core + SM_IDLE 0.90 [10.17%]
==================================================================

[ kprateek: Commit message, SM_RTLOCK_WAIT fix ]

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Not-yet-signed-off-by: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: K Prateek Nayak <kprateek.nayak@amd.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Vincent Guittot <vincent.guittot@linaro.org>
Link: https://lore.kernel.org/r/20240809092240.6921-1-kprateek.nayak@amd.com

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Merge tag 'hwmon-for-v6.11-rc7' into review-hans

Merge "hwmon fixes for v6.11-rc7" into review-hans to bring in
commit a54da9df75cd ("hwmon: (hp-wmi-sensors) Check if WMI event
data exists").

This

Merge tag 'hwmon-for-v6.11-rc7' into review-hans

Merge "hwmon fixes for v6.11-rc7" into review-hans to bring in
commit a54da9df75cd ("hwmon: (hp-wmi-sensors) Check if WMI event
data exists").

This is a dependency for a set of WMI event data refactoring changes.

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sched: Rework dl_server

When a task is selected through a dl_server, it will have p->dl_server
set, such that it can account runtime to the dl_server, see
update_curr_task().

Currently p->dl_server

sched: Rework dl_server

When a task is selected through a dl_server, it will have p->dl_server
set, such that it can account runtime to the dl_server, see
update_curr_task().

Currently p->dl_server is set in pick*task() whenever it goes through
the dl_server, clearing it is a bit of a mess though. The trivial
solution is clearing it on the final put (now that we have this
location).

However, this gives a problem when:

p = pick_task(rq);
if (p)
put_prev_set_next_task(rq, prev, next);

picks the same task but through a different path, notably when it goes
from picking through the dl_server to a direct pick or vice-versa. In
that case we cannot readily determine wether we should clear or
preserve p->dl_server.

An additional complication is pick_*task() setting p->dl_server for a
remote pick, it might still need to update runtime before it schedules
the core_pick.

Close all these holes and remove all the random clearing of
p->dl_server by:

- having pick_*task() manage rq->dl_server

- having the final put_prev_task() clear p->dl_server

- having the first set_next_task() set p->dl_server = rq->dl_server

- complicate the core_sched code to save/restore rq->dl_server where
appropriate.

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lore.kernel.org/r/20240813224016.259853414@infradead.org

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sched: Combine the last put_prev_task() and the first set_next_task()

Ensure the last put_prev_task() and the first set_next_task() always
go together.

Signed-off-by: Peter Zijlstra (Intel) <peterz

sched: Combine the last put_prev_task() and the first set_next_task()

Ensure the last put_prev_task() and the first set_next_task() always
go together.

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lore.kernel.org/r/20240813224016.158454756@infradead.org

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sched: Rework pick_next_task()

The current rule is that:

pick_next_task() := pick_task() + set_next_task(.first = true)

And many classes implement it directly as such. Change things around
to ma

sched: Rework pick_next_task()

The current rule is that:

pick_next_task() := pick_task() + set_next_task(.first = true)

And many classes implement it directly as such. Change things around
to make pick_next_task() optional while also changing the definition to:

pick_next_task(prev) := pick_task() + put_prev_task() + set_next_task(.first = true)

The reason is that sched_ext would like to have a 'final' call that
knows the next task. By placing put_prev_task() right next to
set_next_task() (as it already is for sched_core) this becomes
trivial.

As a bonus, this is a nice cleanup on its own.

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lore.kernel.org/r/20240813224016.051225657@infradead.org

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sched: Split up put_prev_task_balance()

With the goal of pushing put_prev_task() after pick_task() / into
pick_next_task().

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https:

sched: Split up put_prev_task_balance()

With the goal of pushing put_prev_task() after pick_task() / into
pick_next_task().

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lore.kernel.org/r/20240813224015.943143811@infradead.org

show more ...

sched: Use set_next_task(.first) where required

Turns out the core_sched bits forgot to use the
set_next_task(.first=true) variant. Notably:

pick_next_task() := pick_task() + set_next_task(.first

sched: Use set_next_task(.first) where required

Turns out the core_sched bits forgot to use the
set_next_task(.first=true) variant. Notably:

pick_next_task() := pick_task() + set_next_task(.first = true)

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lore.kernel.org/r/20240813224015.614146342@infradead.org

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Merge drm/drm-next into drm-intel-next

Need to take some Xe bo definition in here before
we can add the BMG display 64k aligned size restrictions.

Signed-off-by: Rodrigo Vivi <rodrigo.vivi@intel.co

Merge drm/drm-next into drm-intel-next

Need to take some Xe bo definition in here before
we can add the BMG display 64k aligned size restrictions.

Signed-off-by: Rodrigo Vivi <rodrigo.vivi@intel.com>

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sched/eevdf: Use sched_attr::sched_runtime to set request/slice suggestion

Allow applications to directly set a suggested request/slice length using
sched_attr::sched_runtime.

The implementation cl

sched/eevdf: Use sched_attr::sched_runtime to set request/slice suggestion

Allow applications to directly set a suggested request/slice length using
sched_attr::sched_runtime.

The implementation clamps the value to: 0.1[ms] <= slice <= 100[ms]
which is 1/10 the size of HZ=1000 and 10 times the size of HZ=100.

Applications should strive to use their periodic runtime at a high
confidence interval (95%+) as the target slice. Using a smaller slice
will introduce undue preemptions, while using a larger value will
increase latency.

For all the following examples assume a scheduling quantum of 8, and for
consistency all examples have W=4:

{A,B,C,D}(w=1,r=8):

ABCD...
+---+---+---+---

t=0, V=1.5 t=1, V=3.5
A |------< A |------<
B |------< B |------<
C |------< C |------<
D |------< D |------<
---+*------+-------+--- ---+--*----+-------+---

t=2, V=5.5 t=3, V=7.5
A |------< A |------<
B |------< B |------<
C |------< C |------<
D |------< D |------<
---+----*--+-------+--- ---+------*+-------+---

Note: 4 identical tasks in FIFO order

~~~

{A,B}(w=1,r=16) C(w=2,r=16)

AACCBBCC...
+---+---+---+---

t=0, V=1.25 t=2, V=5.25
A |--------------< A |--------------<
B |--------------< B |--------------<
C |------< C |------<
---+*------+-------+--- ---+----*--+-------+---

t=4, V=8.25 t=6, V=12.25
A |--------------< A |--------------<
B |--------------< B |--------------<
C |------< C |------<
---+-------*-------+--- ---+-------+---*---+---

Note: 1 heavy task -- because q=8, double r such that the deadline of the w=2
task doesn't go below q.

Note: observe the full schedule becomes: W*max(r_i/w_i) = 4*2q = 8q in length.

Note: the period of the heavy task is half the full period at:
W*(r_i/w_i) = 4*(2q/2) = 4q

~~~

{A,C,D}(w=1,r=16) B(w=1,r=8):

BAACCBDD...
+---+---+---+---

t=0, V=1.5 t=1, V=3.5
A |--------------< A |---------------<
B |------< B |------<
C |--------------< C |--------------<
D |--------------< D |--------------<
---+*------+-------+--- ---+--*----+-------+---

t=3, V=7.5 t=5, V=11.5
A |---------------< A |---------------<
B |------< B |------<
C |--------------< C |--------------<
D |--------------< D |--------------<
---+------*+-------+--- ---+-------+--*----+---

t=6, V=13.5
A |---------------<
B |------<
C |--------------<
D |--------------<
---+-------+----*--+---

Note: 1 short task -- again double r so that the deadline of the short task
won't be below q. Made B short because its not the leftmost task, but is
eligible with the 0,1,2,3 spread.

Note: like with the heavy task, the period of the short task observes:
W*(r_i/w_i) = 4*(1q/1) = 4q

~~~

A(w=1,r=16) B(w=1,r=8) C(w=2,r=16)

BCCAABCC...
+---+---+---+---

t=0, V=1.25 t=1, V=3.25
A |--------------< A |--------------<
B |------< B |------<
C |------< C |------<
---+*------+-------+--- ---+--*----+-------+---

t=3, V=7.25 t=5, V=11.25
A |--------------< A |--------------<
B |------< B |------<
C |------< C |------<
---+------*+-------+--- ---+-------+--*----+---

t=6, V=13.25
A |--------------<
B |------<
C |------<
---+-------+----*--+---

Note: 1 heavy and 1 short task -- combine them all.

Note: both the short and heavy task end up with a period of 4q

~~~

A(w=1,r=16) B(w=2,r=16) C(w=1,r=8)

BBCAABBC...
+---+---+---+---

t=0, V=1 t=2, V=5
A |--------------< A |--------------<
B |------< B |------<
C |------< C |------<
---+*------+-------+--- ---+----*--+-------+---

t=3, V=7 t=5, V=11
A |--------------< A |--------------<
B |------< B |------<
C |------< C |------<
---+------*+-------+--- ---+-------+--*----+---

t=7, V=15
A |--------------<
B |------<
C |------<
---+-------+------*+---

Note: as before but permuted

~~~

From all this it can be deduced that, for the steady state:

- the total period (P) of a schedule is: W*max(r_i/w_i)
- the average period of a task is: W*(r_i/w_i)
- each task obtains the fair share: w_i/W of each full period P

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Tested-by: Valentin Schneider <vschneid@redhat.com>
Link: https://lkml.kernel.org/r/20240727105030.842834421@infradead.org

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sched: Teach dequeue_task() about special task states

Since special task states must not suffer spurious wakeups, and the
proposed delayed dequeue can cause exactly these (under some boundary
condit

sched: Teach dequeue_task() about special task states

Since special task states must not suffer spurious wakeups, and the
proposed delayed dequeue can cause exactly these (under some boundary
conditions), propagate this knowledge into dequeue_task() such that it
can do the right thing.

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Valentin Schneider <vschneid@redhat.com>
Tested-by: Valentin Schneider <vschneid@redhat.com>
Link: https://lkml.kernel.org/r/20240727105030.110439521@infradead.org

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sched/uclamg: Handle delayed dequeue

Delayed dequeue has tasks sit around on the runqueue that are not
actually runnable -- specifically, they will be dequeued the moment
they get picked.

One side-

sched/uclamg: Handle delayed dequeue

Delayed dequeue has tasks sit around on the runqueue that are not
actually runnable -- specifically, they will be dequeued the moment
they get picked.

One side-effect is that such a task can get migrated, which leads to a
'nested' dequeue_task() scenario that messes up uclamp if we don't
take care.

Notably, dequeue_task(DEQUEUE_SLEEP) can 'fail' and keep the task on
the runqueue. This however will have removed the task from uclamp --
per uclamp_rq_dec() in dequeue_task(). So far so good.

However, if at that point the task gets migrated -- or nice adjusted
or any of a myriad of operations that does a dequeue-enqueue cycle --
we'll pass through dequeue_task()/enqueue_task() again. Without
modification this will lead to a double decrement for uclamp, which is
wrong.

Reported-by: Luis Machado <luis.machado@arm.com>
Reported-by: Hongyan Xia <hongyan.xia2@arm.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Valentin Schneider <vschneid@redhat.com>
Tested-by: Valentin Schneider <vschneid@redhat.com>
Link: https://lkml.kernel.org/r/20240727105029.315205425@infradead.org

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sched: Prepare generic code for delayed dequeue

While most of the delayed dequeue code can be done inside the
sched_class itself, there is one location where we do not have an
appropriate hook, name

sched: Prepare generic code for delayed dequeue

While most of the delayed dequeue code can be done inside the
sched_class itself, there is one location where we do not have an
appropriate hook, namely ttwu_runnable().

Add an ENQUEUE_DELAYED call to the on_rq path to deal with waking
delayed dequeue tasks.

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Valentin Schneider <vschneid@redhat.com>
Tested-by: Valentin Schneider <vschneid@redhat.com>
Link: https://lkml.kernel.org/r/20240727105029.200000445@infradead.org

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sched: Split DEQUEUE_SLEEP from deactivate_task()

As a preparation for dequeue_task() failing, and a second code-path
needing to take care of the 'success' path, split out the DEQEUE_SLEEP
path from

sched: Split DEQUEUE_SLEEP from deactivate_task()

As a preparation for dequeue_task() failing, and a second code-path
needing to take care of the 'success' path, split out the DEQEUE_SLEEP
path from deactivate_task().

Much thanks to Libo for spotting and fixing a TASK_ON_RQ_MIGRATING
ordering fail.

Fixed-by: Libo Chen <libo.chen@oracle.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Valentin Schneider <vschneid@redhat.com>
Tested-by: Valentin Schneider <vschneid@redhat.com>
Link: https://lkml.kernel.org/r/20240727105029.086192709@infradead.org

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sched: Allow sched_class::dequeue_task() to fail

Change the function signature of sched_class::dequeue_task() to return
a boolean, allowing future patches to 'fail' dequeue.

Signed-off-by: Peter Zi

sched: Allow sched_class::dequeue_task() to fail

Change the function signature of sched_class::dequeue_task() to return
a boolean, allowing future patches to 'fail' dequeue.

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Valentin Schneider <vschneid@redhat.com>
Tested-by: Valentin Schneider <vschneid@redhat.com>
Link: https://lkml.kernel.org/r/20240727105028.864630153@infradead.org

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Merge drm/drm-next into drm-xe-next

Get drm-xe-next on v6.11-rc2 and synchronized with drm-intel-next for
the display side. This resolves the current conflict for the
enable_display module parameter

Merge drm/drm-next into drm-xe-next

Get drm-xe-next on v6.11-rc2 and synchronized with drm-intel-next for
the display side. This resolves the current conflict for the
enable_display module parameter and allows further pending refactors.

Signed-off-by: Lucas De Marchi <lucas.demarchi@intel.com>

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Merge drm/drm-next into drm-misc-next

Get drm-misc-next to the state of v6.11-rc2.

Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>

sched/rt: Rename realtime_{prio, task}() to rt_or_dl_{prio, task}()

Some find the name realtime overloaded. Use rt_or_dl() as an
alternative, hopefully better, name.

Suggested-by: Daniel Bristot de

sched/rt: Rename realtime_{prio, task}() to rt_or_dl_{prio, task}()

Some find the name realtime overloaded. Use rt_or_dl() as an
alternative, hopefully better, name.

Suggested-by: Daniel Bristot de Oliveira <bristot@redhat.com>
Signed-off-by: Qais Yousef <qyousef@layalina.io>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lore.kernel.org/r/20240610192018.1567075-4-qyousef@layalina.io

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sched/rt: Clean up usage of rt_task()

rt_task() checks if a task has RT priority. But depends on your
dictionary, this could mean it belongs to RT class, or is a 'realtime'
task, which includes RT a

sched/rt: Clean up usage of rt_task()

rt_task() checks if a task has RT priority. But depends on your
dictionary, this could mean it belongs to RT class, or is a 'realtime'
task, which includes RT and DL classes.

Since this has caused some confusion already on discussion [1], it
seemed a clean up is due.

I define the usage of rt_task() to be tasks that belong to RT class.
Make sure that it returns true only for RT class and audit the users and
replace the ones required the old behavior with the new realtime_task()
which returns true for RT and DL classes. Introduce similar
realtime_prio() to create similar distinction to rt_prio() and update
the users that required the old behavior to use the new function.

Move MAX_DL_PRIO to prio.h so it can be used in the new definitions.

Document the functions to make it more obvious what is the difference
between them. PI-boosted tasks is a factor that must be taken into
account when choosing which function to use.

Rename task_is_realtime() to realtime_task_policy() as the old name is
confusing against the new realtime_task().

No functional changes were intended.

[1] https://lore.kernel.org/lkml/20240506100509.GL40213@noisy.programming.kicks-ass.net/

Signed-off-by: Qais Yousef <qyousef@layalina.io>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Phil Auld <pauld@redhat.com>
Reviewed-by: "Steven Rostedt (Google)" <rostedt@goodmis.org>
Reviewed-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Link: https://lore.kernel.org/r/20240610192018.1567075-2-qyousef@layalina.io

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Merge drm/drm-next into drm-intel-next

Sync with v6.11-rc1 in general, and specifically get the new
BACKLIGHT_POWER_ constants for power states.

Signed-off-by: Jani Nikula <jani.nikula@intel.com>

sched/rt: Remove default bandwidth control

Now that fair_server exists, we no longer need RT bandwidth control
unless RT_GROUP_SCHED.

Enable fair_server with parameters equivalent to RT throttling.

sched/rt: Remove default bandwidth control

Now that fair_server exists, we no longer need RT bandwidth control
unless RT_GROUP_SCHED.

Enable fair_server with parameters equivalent to RT throttling.

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: "Peter Zijlstra (Intel)" <peterz@infradead.org>
Signed-off-by: Daniel Bristot de Oliveira <bristot@kernel.org>
Signed-off-by: "Vineeth Pillai (Google)" <vineeth@bitbyteword.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Tested-by: Juri Lelli <juri.lelli@redhat.com>
Link: https://lore.kernel.org/r/14d562db55df5c3c780d91940743acb166895ef7.1716811044.git.bristot@kernel.org

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sched/core: Fix priority checking for DL server picks

In core scheduling, a DL server pick (which is CFS task) should be
given higher priority than tasks in other classes.

Not doing so causes CFS s

sched/core: Fix priority checking for DL server picks

In core scheduling, a DL server pick (which is CFS task) should be
given higher priority than tasks in other classes.

Not doing so causes CFS starvation. A kselftest is added later to
demonstrate this. A CFS task that is competing with RT tasks can
be completely starved without this and the DL server's boosting
completely ignored.

Fix these problems.

Reported-by: Suleiman Souhlal <suleiman@google.com>
Signed-off-by: "Joel Fernandes (Google)" <joel@joelfernandes.org>
Signed-off-by: Daniel Bristot de Oliveira <bristot@kernel.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Vineeth Pillai <vineeth@bitbyteword.org>
Tested-by: Juri Lelli <juri.lelli@redhat.com>
Link: https://lore.kernel.org/r/48b78521d86f3b33c24994d843c1aad6b987dda9.1716811044.git.bristot@kernel.org

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sched/fair: Add trivial fair server

Use deadline servers to service fair tasks.

This patch adds a fair_server deadline entity which acts as a container
for fair entities and can be used to fix star

sched/fair: Add trivial fair server

Use deadline servers to service fair tasks.

This patch adds a fair_server deadline entity which acts as a container
for fair entities and can be used to fix starvation when higher priority
(wrt fair) tasks are monopolizing CPU(s).

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Daniel Bristot de Oliveira <bristot@kernel.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Tested-by: Juri Lelli <juri.lelli@redhat.com>
Link: https://lore.kernel.org/r/b6b0bcefaf25391bcf5b6ecdb9f1218de402d42e.1716811044.git.bristot@kernel.org

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