Merge tag 'sched_ext-for-6.12-rc1-fixes-1' of git://git.kernel.org/pub/scm/linux...

Merge tag 'sched_ext-for-6.12-rc1-fixes-1' of git://git./linux/kernel/git/tj/sched_ext

Pull sched_ext fixes from Tejun Heo:

 - When sched_ext is in bypass mode (e.g. while disabling the BPF
   scheduler), it was using one DSQ to implement global FIFO scheduling
   as all it has to do is guaranteeing reasonable forward progress.

   On multi-socket machines, this can lead to live-lock conditions under
   certain workloads. Fixed by splitting the queue used for FIFO
   scheduling per NUMA node. This required several preparation patches.

 - Hotplug tests on powerpc could reliably trigger deadlock while
   enabling a BPF scheduler.

   This was caused by cpu_hotplug_lock nesting inside scx_fork_rwsem and
   then CPU hotplug path trying to fork a new thread while holding
   cpu_hotplug_lock.

   Fixed by restructuring locking in enable and disable paths so that
   the two locks are not coupled. This required several preparation
   patches which also fixed a couple other issues in the enable path.

 - A build fix for !CONFIG_SMP

 - Userspace tooling sync and updates

* tag 'sched_ext-for-6.12-rc1-fixes-1' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/sched_ext:
  sched_ext: Remove redundant p->nr_cpus_allowed checker
  sched_ext: Decouple locks in scx_ops_enable()
  sched_ext: Decouple locks in scx_ops_disable_workfn()
  sched_ext: Add scx_cgroup_enabled to gate cgroup operations and fix scx_tg_online()
  sched_ext: Enable scx_ops_init_task() separately
  sched_ext: Fix SCX_TASK_INIT -> SCX_TASK_READY transitions in scx_ops_enable()
  sched_ext: Initialize in bypass mode
  sched_ext: Remove SCX_OPS_PREPPING
  sched_ext: Relocate check_hotplug_seq() call in scx_ops_enable()
  sched_ext: Use shorter slice while bypassing
  sched_ext: Split the global DSQ per NUMA node
  sched_ext: Relocate find_user_dsq()
  sched_ext: Allow only user DSQs for scx_bpf_consume(), scx_bpf_dsq_nr_queued() and bpf_iter_scx_dsq_new()
  scx_flatcg: Use a user DSQ for fallback instead of SCX_DSQ_GLOBAL
  tools/sched_ext: Receive misc updates from SCX repo
  sched_ext: Add __COMPAT helpers for features added during v6.12 devel cycle
  sched_ext: Build fix for !CONFIG_SMP