From 477869bfafea65492d23de62c1b5208147c09dd2 Mon Sep 17 00:00:00 2001 From: Tejun Heo Date: Thu, 16 Jul 2026 10:43:25 -1000 Subject: sched_ext: Reject setting disallow from init_task outside the enable path The p->scx.disallow revert assumes the root enable path, where the switching loop reads the reverted policy right afterwards and leaves the task off SCX. The sub-scheduler disable path also reaches it when re-initializing the returned tasks on a root parent. Nothing reads the policy there: the task is enabled on root anyway and keeps running on the ext class with a silently rewritten policy. Kill the sched instead, matching the fork and non-root branches, and update the disallow documentation, which equated !fork with the load path and pointed at a stale debugfs path for nr_rejected. Fixes: 337ec00b1d9c ("sched_ext: Implement cgroup sub-sched enabling and disabling") Signed-off-by: Tejun Heo Reviewed-by: Andrea Righi --- include/linux/sched/ext.h | 10 +++++----- 1 file changed, 5 insertions(+), 5 deletions(-) (limited to 'include/linux') diff --git a/include/linux/sched/ext.h b/include/linux/sched/ext.h index 20b2343aa344..87e353f7e011 100644 --- a/include/linux/sched/ext.h +++ b/include/linux/sched/ext.h @@ -244,11 +244,11 @@ struct sched_ext_entity { * to %SCHED_EXT with -%EACCES. * * Can be set from ops.init_task() while the BPF scheduler is being - * loaded (!scx_init_task_args->fork). If set and the task's policy is - * already %SCHED_EXT, the task's policy is rejected and forcefully - * reverted to %SCHED_NORMAL. The number of such events are reported - * through /sys/kernel/debug/sched_ext::nr_rejected. Setting this flag - * during fork is not allowed. + * loaded. If set and the task's policy is already %SCHED_EXT, the + * task's policy is rejected and forcefully reverted to %SCHED_NORMAL. + * The number of such events are reported through + * /sys/kernel/sched_ext/nr_rejected. Setting this flag from any other + * ops.init_task() invocation, such as during fork, fails the scheduler. */ bool disallow; /* reject switching into SCX */ -- cgit v1.2.3