From: Andrea Righi Date: Mon, 8 Jun 2026 16:55:57 +0000 (+0200) Subject: sched_ext: Reset dsq_vtime and slice when a task leaves SCX X-Git-Tag: v7.2-rc4~34^2~12 X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=5771e79e461e72140b752496b69275b9e6bd1a75;p=thirdparty%2Fkernel%2Flinux.git sched_ext: Reset dsq_vtime and slice when a task leaves SCX When a task leaves the BPF scheduler's control, p->scx.dsq_vtime and p->scx.slice keep whatever values they last held. The slice value is core-managed and is refilled on the next enqueue, but dsq_vtime is owned by the BPF scheduler and is never cleared by the core, so a task that leaves SCX and later returns carries a stale dsq_vtime across the round-trip. The stale values are also visible to other SCX schedulers that inspect the scx fields of non-SCX tasks. Fix this by resetting both dsq_vtime and slice in scx_disable_task(), after ops.disable(), so the BPF scheduler can still observe the task's final values and non-SCX tasks do not retain stale SCX state. Signed-off-by: Andrea Righi Signed-off-by: Tejun Heo --- diff --git a/kernel/sched/ext/ext.c b/kernel/sched/ext/ext.c index d62b93f48a85..5efc97437c0a 100644 --- a/kernel/sched/ext/ext.c +++ b/kernel/sched/ext/ext.c @@ -3647,6 +3647,13 @@ static void scx_disable_task(struct scx_sched *sch, struct task_struct *p) SCX_CALL_OP_TASK(sch, disable, rq, p); scx_set_task_state(p, SCX_TASK_READY); + /* + * Reset the SCX-managed fields when @p leaves the BPF scheduler's + * control, after ops.disable() has observed their final values. + */ + p->scx.dsq_vtime = 0; + p->scx.slice = 0; + /* * Verify the task is not in BPF scheduler's custody. If flag * transitions are consistent, the flag should always be clear