sched_ext: Decouple locks in scx_ops_disable_workfn()

The disable path uses three big locks - scx_fork_rwsem, scx_cgroup_rwsem and
cpus_read_lock. Currently, the locks are grabbed together which is prone to
locking order problems. With the preceding scx_cgroup_enabled change, we can
decouple them:

- As cgroup disabling no longer requires modifying a static_key which
  requires cpus_read_lock(), no need to grab cpus_read_lock() before
  grabbing scx_cgroup_rwsem.

- cgroup can now be independently disabled before tasks are moved back to
  the fair class.

Relocate scx_cgroup_exit() invocation before scx_fork_rwsem is grabbed, drop
now unnecessary cpus_read_lock() and move static_key operations out of
scx_fork_rwsem. This decouples all three locks in the disable path.

Signed-off-by: Tejun Heo <[email protected]>
Reported-and-tested-by: Aboorva Devarajan <[email protected]>
Link: http://lkml.kernel.org/r/[email protected]

0 files changed, 0 insertions, 0 deletions