linux.git/kernel/sched/syscalls.c, branch v6.18.21

sched: Deadline has dynamic priority

2026-01-23T10:21:23+00:00

[ Upstream commit e008ec6c7904ed99d3b2cb634b6545b008a99288 ]

While FIFO/RR have static priority, DEADLINE is a dynamic priority
scheme. Notably it has static priority -1. Do not assume the priority
doesn't change for deadline tasks just because the static priority
doesn't change.

This ensures DL always sees {DE,EN}QUEUE_MOVE where appropriate.

Fixes: ff77e4685359 ("sched/rt: Fix PI handling vs. sched_setscheduler()")
Signed-off-by: Peter Zijlstra (Intel) 
Tested-by: Pierre Gondois 
Tested-by: Juri Lelli 
Link: https://patch.msgid.link/20260114130528.GB831285@noisy.programming.kicks-ass.net
Signed-off-by: Sasha Levin

sched/proxy: Yield the donor task

2026-01-08T09:16:41+00:00

commit 127b90315ca07ccad2618db7ba950a63e3b32d22 upstream.

When executing a task in proxy context, handle yields as if they were
requested by the donor task. This matches the traditional PI semantics
of yield() as well.

This avoids scenario like proxy task yielding, pick next task selecting the
same previous blocked donor, running the proxy task again, etc.

Reported-by: kernel test robot 
Closes: https://lore.kernel.org/oe-lkp/202510211205.1e0f5223-lkp@intel.com
Suggested-by: Peter Zijlstra 
Signed-off-by: Fernand Sieber 
Signed-off-by: Peter Zijlstra (Intel) 
Link: https://patch.msgid.link/20251106104022.195157-1-sieberf@amazon.com
Cc: Holger Hoffstätte 
Signed-off-by: Greg Kroah-Hartman

sched/smp: Use the SMP version of the scheduler syscalls

2025-06-13T06:47:21+00:00

Simplify the scheduler by making CONFIG_SMP=y code in
idle_cpu(), __sched_setscheduler() and sched_setaffinity()
unconditional.

Signed-off-by: Ingo Molnar 
Acked-by: Peter Zijlstra 
Cc: Dietmar Eggemann 
Cc: Juri Lelli 
Cc: Linus Torvalds 
Cc: Mel Gorman 
Cc: Sebastian Andrzej Siewior 
Cc: Shrikanth Hegde 
Cc: Steven Rostedt 
Cc: Valentin Schneider 
Cc: Vincent Guittot 
Link: https://lore.kernel.org/r/20250528080924.2273858-33-mingo@kernel.org

sched/smp: Make SMP unconditional

2025-06-13T06:47:18+00:00

Simplify the scheduler by making CONFIG_SMP=y primitives and data
structures unconditional.

Introduce transitory wrappers for functionality not yet converted to SMP.

Note that this patch is pretty large, because there's no clear separation
between various aspects of the SMP scheduler, it's basically a huge block
of #ifdef CONFIG_SMP. A fair amount of it has to be switched on for it to
boot and work on UP systems.

Signed-off-by: Ingo Molnar 
Acked-by: Peter Zijlstra 
Cc: Dietmar Eggemann 
Cc: Juri Lelli 
Cc: Linus Torvalds 
Cc: Mel Gorman 
Cc: Sebastian Andrzej Siewior 
Cc: Shrikanth Hegde 
Cc: Steven Rostedt 
Cc: Valentin Schneider 
Cc: Vincent Guittot 
Link: https://lore.kernel.org/r/20250528080924.2273858-21-mingo@kernel.org

sched: Clean up and standardize #if/#else/#endif markers in sched/syscalls.c

2025-06-13T06:47:18+00:00

 - Use the standard #ifdef marker format for larger blocks,
   where appropriate:

        #if CONFIG_FOO
        ...
        #else /* !CONFIG_FOO: */
        ...
        #endif /* !CONFIG_FOO */

Signed-off-by: Ingo Molnar 
Acked-by: Peter Zijlstra 
Cc: Dietmar Eggemann 
Cc: Juri Lelli 
Cc: Linus Torvalds 
Cc: Mel Gorman 
Cc: Sebastian Andrzej Siewior 
Cc: Shrikanth Hegde 
Cc: Steven Rostedt 
Cc: Valentin Schneider 
Cc: Vincent Guittot 
Link: https://lore.kernel.org/r/20250528080924.2273858-18-mingo@kernel.org

sched: Bypass bandwitdh checks with runtime disabled RT_GROUP_SCHED

2025-04-08T18:55:54+00:00

When RT_GROUPs are compiled but not exposed, their bandwidth cannot
be configured (and it is not initialized for non-root task_groups neither).
Therefore bypass any checks of task vs task_group bandwidth.

This will achieve behavior very similar to setups that have
!CONFIG_RT_GROUP_SCHED and attach cpu controller to cgroup v2 hierarchy.
(On a related note, this may allow having RT tasks with
CONFIG_RT_GROUP_SCHED and cgroup v2 hierarchy.)

Signed-off-by: Michal Koutný 
Signed-off-by: Peter Zijlstra (Intel) 
Link: https://lkml.kernel.org/r/20250310170442.504716-7-mkoutny@suse.com

sched: Convert CONFIG_RT_GROUP_SCHED macros to code conditions

2025-04-08T18:55:52+00:00

Convert the blocks guarded by macros to regular code so that the RT
group code gets more compile validation. Reasoning is in
Documentation/process/coding-style.rst 21) Conditional Compilation.
With that, no functional change is expected.

Signed-off-by: Michal Koutný 
Signed-off-by: Peter Zijlstra (Intel) 
Link: https://lkml.kernel.org/r/20250310170442.504716-2-mkoutny@suse.com

sched/uclamp: Optimize sched_uclamp_used static key enabling

2025-03-15T09:28:50+00:00

Repeat calls of static_branch_enable() to an already enabled
static key introduce overhead, because it calls cpus_read_lock().

Users may frequently set the uclamp value of tasks, triggering
the repeat enabling of the sched_uclamp_used static key.

Optimize this and avoid repeat calls to static_branch_enable()
by checking whether it's enabled already.

[ mingo: Rewrote the changelog for legibility ]

Signed-off-by: Xuewen Yan 
Signed-off-by: Peter Zijlstra (Intel) 
Signed-off-by: Ingo Molnar 
Reviewed-by: Christian Loehle 
Reviewed-by: Vincent Guittot 
Link: https://lore.kernel.org/r/20250219093747.2612-2-xuewen.yan@unisoc.com

sched: Add unlikey branch hints to several system calls

2025-02-21T19:19:13+00:00

Adding an unlikely() hint on early error return paths improves the
run-time performance of several sched related system calls.

Benchmarking on an i9-12900 shows the following per system call
performance improvements:

		       before     after     improvement
sched_getattr          182.4ns    170.6ns      ~6.5%
sched_setattr          284.3ns    267.6ns      ~5.9%
sched_getparam         161.6ns    148.1ns      ~8.4%
sched_setparam        1265.4ns   1227.6ns      ~3.0%
sched_getscheduler     129.4ns    118.2ns      ~8.7%
sched_setscheduler    1237.3ns   1216.7ns      ~1.7%

Results are based on running 20 tests with turbo disabled (to reduce
clock freq turbo changes), with 10 second run per test based on the
number of system calls per second. The % standard deviation of the
measurements for the 20 tests was 0.05% to 0.40%, so the results are
reliable.

Tested on kernel build with gcc 14.2.1

Signed-off-by: Colin Ian King 
Signed-off-by: Peter Zijlstra (Intel) 
Link: https://lkml.kernel.org/r/20250219142423.45516-1-colin.i.king@gmail.com

cpufreq/schedutil: Only bind threads if needed

2025-01-23T20:09:25+00:00

Remove the unconditional binding of sugov kthreads to the affected CPUs
if the cpufreq driver indicates that updates can happen from any CPU.
This allows userspace to set affinities to either save power (waking up
bigger CPUs on HMP can be expensive) or increasing performance (by
letting the utilized CPUs run without preemption of the sugov kthread).

Signed-off-by: Christian Loehle 
Acked-by: Viresh Kumar 
Acked-by: Vincent Guittot 
Acked-by: Rafael J. Wysocki 
Acked-by: Juri Lelli 
Link: https://patch.msgid.link/5a8deed4-7764-4729-a9d4-9520c25fa7e8@arm.com
Signed-off-by: Rafael J. Wysocki