kernel.git/kernel/sched/ext_idle.c, branch linux-6.19.y

sched_ext: Wrap kfunc args in struct to prepare for aux__prog

2025-10-13T18:49:29Z

scx_bpf_dsq_insert_vtime() and scx_bpf_select_cpu_and() currently have 5 parameters. An upcoming change will add aux__prog parameter which will exceed BPF's 5 argument limit. Prepare by adding new kfuncs __scx_bpf_dsq_insert_vtime() and __scx_bpf_select_cpu_and() that take args structs. The existing kfuncs are kept as compatibility wrappers. BPF programs use inline wrappers that detect kernel API version via bpf_core_type_exists() and use the new struct-based kfuncs when available, falling back to compat kfuncs otherwise. This allows BPF programs to work with both old and new kernels. Reviewed-by: Emil Tsalapatis Acked-by: Andrea Righi Signed-off-by: Tejun Heo

sched_ext: Merge branch 'for-6.17-fixes' into for-6.18

2025-09-23T19:10:20Z

Pull sched_ext/for-6.17-fixes to receive: 55ed11b181c4 ("sched_ext: idle: Handle migration-disabled tasks in BPF code") which conflicts with the following commit in for-6.18: 2407bae23d1e ("sched_ext: Add the @sch parameter to ext_idle helpers") The conflict is a simple context conflict which can be resolved by taking the updated parts from both commits. Signed-off-by: Tejun Heo

sched_ext: Drop scx_kf_exit() and scx_kf_error()

2025-09-23T19:03:26Z

The intention behind scx_kf_exit/error() was that when called from kfuncs, scx_kf_exit/error() would be able to implicitly determine the scx_sched instance being operated on and thus wouldn't need the @sch parameter passed in explicitly. This turned out to be unnecessarily complicated to implement and not have enough practical benefits. Replace scx_kf_exit/error() usages with scx_exit/error() which take an explicit @sch parameter. - Add the @sch parameter to scx_kf_allowed(), scx_kf_allowed_on_arg_tasks, mark_direct_dispatch() and other intermediate functions transitively. - In callers that don't already have @sch available, grab RCU, read $scx_root, verify it's not NULL and use it. Reviewed-by: Andrea Righi Signed-off-by: Tejun Heo

sched_ext: Drop kf_cpu_valid()

2025-09-23T19:03:26Z

The intention behind kf_cpu_valid() was that when called from kfuncs, kf_cpu_valid() would be able to implicitly determine the scx_sched instance being operated on and thus wouldn't need @sch passed in explicitly. This turned out to be unnecessarily complicated to implement and not have justifiable practical benefits. Replace kf_cpu_valid() usages with ops_cpu_valid() which takes explicit @sch. Callers which don't have $sch available in the context are updated to read $scx_root under RCU read lock, verify that it's not NULL and pass it in. scx_bpf_cpu_rq() is restructured to use guard(rcu)() instead of explicit rcu_read_[un]lock(). Reviewed-by: Andrea Righi Signed-off-by: Tejun Heo

sched_ext: Add the @sch parameter to ext_idle helpers

2025-09-23T19:03:26Z

In preparation for multiple scheduler support, add the @sch parameter to validate_node(), check_builtin_idle_enabled() and select_cpu_from_kfunc(), and update their callers to read $scx_root, verify that it's not NULL and pass it in. The passed in @sch parameter is not used yet. Reviewed-by: Andrea Righi Signed-off-by: Tejun Heo

sched_ext: idle: Handle migration-disabled tasks in BPF code

2025-09-22T16:24:44Z

When scx_bpf_select_cpu_dfl()/and() kfuncs are invoked outside of ops.select_cpu() we can't rely on @p->migration_disabled to determine if migration is disabled for the task @p. In fact, migration is always disabled for the current task while running BPF code: __bpf_prog_enter() disables migration and __bpf_prog_exit() re-enables it. To handle this, when @p->migration_disabled == 1, check whether @p is the current task. If so, migration was not disabled before entering the callback, otherwise migration was disabled. This ensures correct idle CPU selection in all cases. The behavior of ops.select_cpu() remains unchanged, because this callback is never invoked for the current task and migration-disabled tasks are always excluded. Example: without this change scx_bpf_select_cpu_and() called from ops.enqueue() always returns -EBUSY; with this change applied, it correctly returns idle CPUs. Fixes: 06efc9fe0b8de ("sched_ext: idle: Handle migration-disabled tasks in idle selection") Cc: stable@vger.kernel.org # v6.16+ Signed-off-by: Andrea Righi Acked-by: Changwoo Min Signed-off-by: Tejun Heo

Merge tag 'sched_ext-for-6.17' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/sched_ext

2025-07-31T23:29:46Z

Pull sched_ext updates from Tejun Heo: - Add support for cgroup "cpu.max" interface - Code organization cleanup so that ext_idle.c doesn't depend on the source-file-inclusion build method of sched/ - Drop UP paths in accordance with sched core changes - Documentation and other misc changes * tag 'sched_ext-for-6.17' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/sched_ext: sched_ext: Fix scx_bpf_reenqueue_local() reference sched_ext: Drop kfuncs marked for removal in 6.15 sched_ext, rcu: Eject BPF scheduler on RCU CPU stall panic kernel/sched/ext.c: fix typo "occured" -> "occurred" in comments sched_ext: Add support for cgroup bandwidth control interface sched_ext, sched/core: Factor out struct scx_task_group sched_ext: Return NULL in llc_span sched_ext: Always use SMP versions in kernel/sched/ext_idle.h sched_ext: Always use SMP versions in kernel/sched/ext_idle.c sched_ext: Always use SMP versions in kernel/sched/ext.h sched_ext: Always use SMP versions in kernel/sched/ext.c sched_ext: Documentation: Clarify time slice handling in task lifecycle sched_ext: Make scx_locked_rq() inline sched_ext: Make scx_rq_bypassing() inline sched_ext: idle: Make local functions static in ext_idle.c sched_ext: idle: Remove unnecessary ifdef in scx_bpf_cpu_node()

sched_ext: idle: Handle migration-disabled tasks in idle selection

2025-07-17T18:19:38Z

When SCX_OPS_ENQ_MIGRATION_DISABLED is enabled, migration-disabled tasks are also routed to ops.enqueue(). A scheduler may attempt to dispatch such tasks directly to an idle CPU using the default idle selection policy via scx_bpf_select_cpu_and() or scx_bpf_select_cpu_dfl(). This scenario must be properly handled by the built-in idle policy to avoid returning an idle CPU where the target task isn't allowed to run. Otherwise, it can lead to errors such as: EXIT: runtime error (SCX_DSQ_LOCAL[_ON] cannot move migration disabled Chrome_ChildIOT[291646] from CPU 3 to 14) Prevent this by explicitly handling migration-disabled tasks in the built-in idle selection logic, maintaining their CPU affinity. Fixes: a730e3f7a48bc ("sched_ext: idle: Consolidate default idle CPU selection kfuncs") Signed-off-by: Andrea Righi Signed-off-by: Tejun Heo

sched_ext: Return NULL in llc_span

2025-06-16T17:32:37Z

Use NULL instead of 0 to signal no LLC domain, matching numa_span() and the function comment. No functional change. Signed-off-by: Cheng-Yang Chou Signed-off-by: Tejun Heo

sched_ext: Always use SMP versions in kernel/sched/ext_idle.c

2025-06-14T00:47:52Z

Simplify the scheduler by making formerly SMP-only primitives and data structures unconditional. tj: Updated subject for clarity. Fixed stray #else block which wasn't removed causing build failure. Signed-off-by: Cheng-Yang Chou Signed-off-by: Tejun Heo