sched_ext: Drop unlocked scx_rq_clock_invalidate() from scx_root_disable()

scx_root_disable() invalidates each rq's clock before taking the rq lock.
scx_rq_clock_invalidate() is a plain read-modify-write of rq->scx.flags and
every other writer of the word runs under the rq lock, so the unlocked
update can race a concurrent flags update and lose one side's bits.

The invalidation doesn't matter in the first place. The cached clock is read
only by scx_bpf_now() from a loaded scheduler's BPF programs, nothing can
re-validate the clock while sched_ext is disabled as scx_rq_clock_update()
is gated on scx_enabled() too, and the usual rq lock cycles under the next
scheduler refresh or invalidate it before it's practically observable. Drop
the invalidation instead of fixing the locking.

v2: Description and comment updated - the invalidation is unnecessary rather
    than subsumed by the rq lock cycle below.

Fixes: 3a9910b5904d ("sched_ext: Implement scx_bpf_now()")
Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Changwoo Min <changwoo@igalia.com>

0 files changed, 0 insertions, 0 deletions