From: Andrea Righi Date: Sat, 5 Jul 2025 05:43:51 +0000 (+0200) Subject: sched_ext: idle: Handle migration-disabled tasks in idle selection X-Git-Tag: v6.16-rc7~15^2 X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=06efc9fe0b8deeb83b47fd7c5451fe1a60c8a761;p=thirdparty%2Flinux.git sched_ext: idle: Handle migration-disabled tasks in idle selection 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 --- diff --git a/kernel/sched/ext_idle.c b/kernel/sched/ext_idle.c index 6d29d3cbc670..001fb88a8481 100644 --- a/kernel/sched/ext_idle.c +++ b/kernel/sched/ext_idle.c @@ -903,7 +903,7 @@ s32 select_cpu_from_kfunc(struct task_struct *p, s32 prev_cpu, u64 wake_flags, * selection optimizations and simply check whether the previously * used CPU is idle and within the allowed cpumask. */ - if (p->nr_cpus_allowed == 1) { + if (p->nr_cpus_allowed == 1 || is_migration_disabled(p)) { if (cpumask_test_cpu(prev_cpu, allowed ?: p->cpus_ptr) && scx_idle_test_and_clear_cpu(prev_cpu)) cpu = prev_cpu;