user/sven/linux.git/kernel/sched/syscalls.c, branch v6.18.1

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

2025-06-13T06:47:21Z

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

2025-06-13T06:47:18Z

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

2025-06-13T06:47:18Z

- 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

2025-04-08T18:55:54Z

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

2025-04-08T18:55:52Z

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

2025-03-15T09:28:50Z

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

2025-02-21T19:19:13Z

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

2025-01-23T20:09:25Z

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

sched/fair: Encapsulate set custom slice in a __setparam_fair() function

2025-01-13T13:10:22Z

Similarly to dl, create a __setparam_fair() function to set parameters related to fair class and move it in the fair.c file. No functional changes expected Signed-off-by: Vincent Guittot Signed-off-by: Peter Zijlstra (Intel) Reviewed-by: Phil Auld Link: https://lore.kernel.org/r/20250110144656.484601-1-vincent.guittot@linaro.org

sched: Fix race between yield_to() and try_to_wake_up()

2025-01-13T13:10:22Z

We met a SCHED_WARN in set_next_buddy(): __warn_printk set_next_buddy yield_to_task_fair yield_to kvm_vcpu_yield_to [kvm] ... After a short dig, we found the rq_lock held by yield_to() may not be exactly the rq that the target task belongs to. There is a race window against try_to_wake_up(). CPU0 target_task blocking on CPU1 lock rq0 & rq1 double check task_rq == p_rq, ok woken to CPU2 (lock task_pi & rq2) task_rq = rq2 yield_to_task_fair (w/o lock rq2) In this race window, yield_to() is operating the task w/o the correct lock. Fix this by taking task pi_lock first. Fixes: d95f41220065 ("sched: Add yield_to(task, preempt) functionality") Signed-off-by: Tianchen Ding Signed-off-by: Peter Zijlstra (Intel) Link: https://lkml.kernel.org/r/20241231055020.6521-1-dtcccc@linux.alibaba.com