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commitf0c6eab5e4upstream. A BPF scheduler may want to use the built-in idle cpumasks in ops.init() before the scheduler is fully initialized, either directly or through a BPF timer for example. However, this would result in an error, since the idle state has not been properly initialized yet. This can be easily verified by modifying scx_simple to call scx_bpf_get_idle_cpumask() in ops.init(): $ sudo scx_simple DEBUG DUMP =========================================================================== scx_simple[121] triggered exit kind 1024: runtime error (built-in idle tracking is disabled) ... Fix this by properly initializing the idle state before ops.init() is called. With this change applied: $ sudo scx_simple local=2 global=0 local=19 global=11 local=23 global=11 ... Fixes:d73249f887("sched_ext: idle: Make idle static keys private") Signed-off-by: Andrea Righi <arighi@nvidia.com> Reviewed-by: Joel Fernandes <joelagnelf@nvidia.com> Signed-off-by: Tejun Heo <tj@kernel.org> [ Backport to 6.12: - Original commit doesn't apply cleanly to 6.12 sinced73249f887is not present. - This backport applies the same logical fix to prevent BPF scheduler failures while accessing idle cpumasks from ops.init(). ] Signed-off-by: Andrea Righi <arighi@nvidia.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>