tree 72eda88ab241d491ec3b6ec52f31b5f55a4324eb
parent 40d8c81577db09b71ee5402ba336b642d32d6a82
parent fab183d632628381b466a41479489541ac0e29a0
author Linus Torvalds <torvalds@linux-foundation.org> 1787248897 -0700
committer Linus Torvalds <torvalds@linux-foundation.org> 1787248897 -0700
mergetag object fab183d632628381b466a41479489541ac0e29a0
 type commit
 tag sched_ext-for-7.3
 tagger Tejun Heo <tj@kernel.org> 1787003119 -1000
 
 sched_ext: Changes for v7.3
 
 This depends on the arena argument support in the BPF tree and should be
 pulled after the scheduler core and BPF pulls. The patches based on bpf-next
 were kept on a separate branch which was merged into for-7.3 just now. The
 same merged result was in linux-next for several days.
 
 Most of this cycle completes the enqueue-path support for hierarchical
 sub-scheduling, which makes sub-scheduler support feature complete: a root
 BPF scheduler can now hand a cgroup subtree over to a nested sub-scheduler
 together with revocable CPU grants, and the sub-scheduler owns all
 scheduling decisions for its tasks on those CPUs.
 
 Development volume was high and a number of changes plugging holes in the
 new support landed late in the cycle. Also included are core scheduling
 fixes that were completed too late for the v7.2 release and are routed
 through this pull request.
 
 - Sub-scheduler CPU delegation:
 
   - Parent schedulers now grant and revoke per-CPU capabilities (enqueueing,
     preemption, CPU frequency control) on their children, enforced on every
     path a scheduler can reach a CPU through. Previously only dispatching
     could be delegated; this lets sub-schedulers fully schedule their CPUs.
 
   - Rescue execution: a task whose scheduler doesn't have access to the CPUs
     the task needs to run on starved until the watchdog ejected the whole
     scheduler. The kernel now runs such tasks directly on a small bandwidth
     budget, turning a scheduler-killing failure into bounded degradation.
 
   - Cgroup integration: tasks migrating across a sub-scheduler boundary
     weren't re-homed to the new owner, causing wrong-scheduler scheduling
     and a use-after-free. Sub-schedulers now take over their cgroup subtree
     and receive its cgroup callbacks.
 
   - Arena objects now cross the kernel/BPF boundary as typed pointer
     arguments, translated transparently by the BPF tree's new arena argument
     support, replacing untyped arguments with manual translation.
 
   - scx_qmap now demonstrates full hierarchical sub-scheduling.
 
 - Robustness improvements: the abort path is now NMI-safe, fixing deadlocks
   when errors are raised from NMI context and making hardlockup recovery
   direct. Reenqueue loops that could monopolize a CPU ahead of the watchdog
   now eject the offending scheduler, and stalls are blamed on the scheduler
   actually responsible.
 
 - Hardening: BPF-writable arena memory is validated before kernel use, and
   task slice and vtime writes got explicit synchronization rules, closing
   corruption vectors open to buggy or malicious schedulers.
 
 - Core scheduling: sched_ext dispatching can drop the rq lock inside the
   core-wide pick, which let interleaving selections corrupt each other's
   state and hard-hang the machine. The selection now restarts when the lock
   was released. The task ordering callback was also invoked with its
   arguments swapped, and the default ordering is updated to work across
   sub-scheduler boundaries. The fixes are marked for stable.
 
 - Other fixes headed for stable: a task init leak on fork failure during
   enable, tooling compat macros that silently failed to detect newer
   kernels, and a crash on reenqueueing against a destroyed dispatch queue.
 
 - Tooling: scx_pair moves off deprecated callbacks, and the deprecated
   scx_bpf_cpu_rq() kfunc is removed.
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Merge tag 'sched_ext-for-7.3' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/sched_ext

Pull sched_ext updates from Tejun Heo:
 "Most of this cycle completes the enqueue-path support for hierarchical
  sub-scheduling, which makes sub-scheduler support feature complete: a
  root BPF scheduler can now hand a cgroup subtree over to a nested
  sub-scheduler together with revocable CPU grants, and the
  sub-scheduler owns all scheduling decisions for its tasks on those
  CPUs.

  Development volume was high and a number of changes plugging holes in
  the new support landed late in the cycle. Also included are core
  scheduling fixes that were completed too late for the v7.2 release and
  are routed through this pull request.

  Sub-scheduler CPU delegation:

   - Parent schedulers now grant and revoke per-CPU capabilities
     (enqueueing, preemption, CPU frequency control) on their children,
     enforced on every path a scheduler can reach a CPU through.
     Previously only dispatching could be delegated; this lets
     sub-schedulers fully schedule their CPUs.

   - Rescue execution: a task whose scheduler doesn't have access to the
     CPUs the task needs to run on starved until the watchdog ejected
     the whole scheduler. The kernel now runs such tasks directly on a
     small bandwidth budget, turning a scheduler-killing failure into
     bounded degradation.

   - Cgroup integration: tasks migrating across a sub-scheduler boundary
     weren't re-homed to the new owner, causing wrong-scheduler
     scheduling and a use-after-free. Sub-schedulers now take over their
     cgroup subtree and receive its cgroup callbacks.

   - Arena objects now cross the kernel/BPF boundary as typed pointer
     arguments, translated transparently by the BPF tree's new arena
     argument support, replacing untyped arguments with manual
     translation.

   - scx_qmap now demonstrates full hierarchical sub-scheduling.

  Other fixes and updates:

   - Robustness improvements: the abort path is now NMI-safe, fixing
     deadlocks when errors are raised from NMI context and making
     hardlockup recovery direct. Reenqueue loops that could monopolize a
     CPU ahead of the watchdog now eject the offending scheduler, and
     stalls are blamed on the scheduler actually responsible.

   - Hardening: BPF-writable arena memory is validated before kernel
     use, and task slice and vtime writes got explicit synchronization
     rules, closing corruption vectors open to buggy or malicious
     schedulers.

   - Core scheduling: sched_ext dispatching can drop the rq lock inside
     the core-wide pick, which let interleaving selections corrupt each
     other's state and hard-hang the machine. The selection now restarts
     when the lock was released. The task ordering callback was also
     invoked with its arguments swapped, and the default ordering is
     updated to work across sub-scheduler boundaries. The fixes are
     marked for stable.

   - Other fixes headed for stable: a task init leak on fork failure
     during enable, tooling compat macros that silently failed to detect
     newer kernels, and a crash on reenqueueing against a destroyed
     dispatch queue.

   - Tooling: scx_pair moves off deprecated callbacks, and the
     deprecated scx_bpf_cpu_rq() kfunc is removed"

* tag 'sched_ext-for-7.3' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/sched_ext: (144 commits)
  sched_ext: Drop the dead SCX_DEQ_CORE_SCHED_EXEC test in dequeue_task_scx()
  sched_ext: Make core-sched task ordering hierarchy-aware
  sched_ext: Use runnable_at for the default core-sched task ordering
  sched_ext: Fix inverted ops.core_sched_before() invocation
  sched_ext: Move the config-off sub-cap kfunc stubs into sub.c
  sched_ext: Rename balance-era identifiers to dispatch terms
  sched_ext: Drop the stale keep_prev fixup in dispatch_pick()
  sched_ext: Keep kick_sync waiting on the rq's own CPU
  sched_ext: Make SCHED_CLASS_EXT select GENERIC_ALLOCATOR
  sched_ext/scx_flatcg: Fix cvtime true-up on slice expiry
  sched_ext: Don't BUG_ON a destroyed DSQ in process_deferred_reenq_users
  sched_ext: Fix scx_bpf_dsq_move_to_local___v2 compat detection
  sched_ext: Make scx_bpf_events() read the calling scheduler's counters
  sched_ext: Drop unlocked scx_rq_clock_invalidate() from scx_root_disable()
  selftests/sched_ext: Fix flaky ddsp failure tests on busy systems
  selftests/sched_ext: Make numa idle validation race-free
  sched_ext: Fix scx_bpf_dsq_reenq___compat kfunc extern prototype
  sched_ext/scx_flatcg: expire cached hweights on weight changes
  sched_ext: Fix exit_task leak on fork failure during enable
  sched_ext: fix stale references in doc comments
  ...