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sched_ext: Fixes for v7.3-rc6

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- Taking a CPU offline could hang, or stall until the watchdog ejected the
   BPF scheduler, when tasks on the dying CPU were still held by the
   scheduler or sitting on a user dispatch queue. Re-enqueue them onto the
   local queue when the runqueue goes offline so that the CPU pushes them off
   like the other sched classes.
 
 - The sequence number guarding against stale dispatches was per runqueue, so
   a task re-enqueued on another CPU could get the same number and a dispatch
   meant for its earlier instance was applied to the new one. Use a per-task
   counter.
 
 - A task dispatched to another CPU's local queue got its ops.dequeue() only
   when picked to run and flagged as a core-sched pick. Call it at insertion
   like for same-CPU dispatches.
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Merge tag 'sched_ext-for-7.3-rc6-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/sched_ext

Pull sched_ext fixes from Tejun Heo:

 - Taking a CPU offline could hang, or stall until the watchdog ejected
   the BPF scheduler, when tasks on the dying CPU were still held by the
   scheduler or sitting on a user dispatch queue. Re-enqueue them onto
   the local queue when the runqueue goes offline so that the CPU pushes
   them off like the other sched classes.

 - The sequence number guarding against stale dispatches was per
   runqueue, so a task re-enqueued on another CPU could get the same
   number and a dispatch meant for its earlier instance was applied to
   the new one. Use a per-task counter.

 - A task dispatched to another CPU's local queue got its ops.dequeue()
   only when picked to run and flagged as a core-sched pick. Call it at
   insertion like for same-CPU dispatches.

* tag 'sched_ext-for-7.3-rc6-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/sched_ext:
  sched_ext: Generate qseq from a per-task counter
  selftests/sched_ext: Add a test for ops.dequeue() on remote local DSQ moves
  sched_ext: Call ops.dequeue() when a task arrives on a remote local DSQ
  sched_ext: Fix CPU hotplug hang when a dying CPU's tasks sit in the BPF scheduler
This commit is contained in:
Linus Torvalds 2026-10-07 02:03:46 +02:00
commit 762122d75e
9 changed files with 528 additions and 17 deletions
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