SCX_DSQ_GLOBAL now does not support vtime dispatching. scx_simple uses
it to do vtime scheduling, so let's update it to create and use a
separate DSQ that it can both FIFO and PRIQ dispatch to.
Signed-off-by: David Vernet <void@manifault.com>
tp_cgroup_attach_task() walks p->thread_group to visit all member threads
and set tctx->refresh_layer. However, the upstream kernel has removed
p->thread_group recently in 8e1f385104ac ("kill task_struct->thread_group")
as it was mostly a duplicate of p->signal->thread_head list which goes
through p->thread_node.
Switch to iterate via p->thread_node instead, add a comment explaining why
it's using the cgroup TP instead of scx_ops.cgroup_move(), and make
iteration failure non-fatal as the iteration is racy.
As in scx_layered, bpf_map_delete_elem() can fail due to recursion
protection triggering spuriously which can then lead to task_ctx creation
failure after PIDs wrap. Work around by dropping BPF_NOEXIST.
The scx repo is going to serve as the source of truth for sched_ext
schedulers. Reverse the sync direction and include syncing rust-user
schedulers too.
