Merge tag 'wq-for-6.13' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/wq

Merge tag 'wq-for-6.13' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/wq

Pull workqueue updates from Tejun Heo:

 - The maximum concurrency limit of 512 which was set a long time ago is
   too low now.

   A legitimate use (BPF cgroup release) of system_wq could saturate it
   under stress test conditions leading to false dependencies and
   deadlocks.

   While the offending use was switched to a dedicated workqueue, use
   the opportunity to bump WQ_MAX_ACTIVE four fold and document that
   system workqueue shouldn't be saturated. Workqueue should add at
   least a warning mechanism for cases where system workqueues are
   saturated.

 - Recent workqueue updates to support more flexible execution topology
   made unbound workqueues use per-cpu worker pool frontends which
   pushed up workqueue flush overhead.

   As consecutive CPUs are likely to be pointing to the same worker
   pool, reduce overhead by switching locks only when necessary.

* tag 'wq-for-6.13' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/wq:
  workqueue: Reduce expensive locks for unbound workqueue
  workqueue: Adjust WQ_MAX_ACTIVE from 512 to 2048
  workqueue: doc: Add a note saturating the system_wq is not permitted