sched_ext: ops.cpu_acquire() should be called with SCX_KF_REST

ops.cpu_acquire() is currently called with 0 kf_maks which is interpreted as
SCX_KF_UNLOCKED which allows all unlocked kfuncs, but ops.cpu_acquire() is
called from balance_one() under the rq lock and should only be allowed call
kfuncs that are safe under the rq lock. Update it to use SCX_KF_REST.

Signed-off-by: Tejun Heo <[email protected]>
Cc: David Vernet <[email protected]>
Cc: Zhao Mengmeng <[email protected]>
Link: http://lkml.kernel.org/r/[email protected]
Fixes: 245254f ("sched_ext: Implement sched_ext_ops.cpu_acquire/release()")

Author: htejun

kernel/sched/ext.c

@@ -2645,7 +2645,7 @@ static int balance_one(struct rq *rq, struct task_struct *prev)
 		 * emitted in scx_next_task_picked().
 		 */
 		if (SCX_HAS_OP(cpu_acquire))
-			SCX_CALL_OP(0, cpu_acquire, cpu_of(rq), NULL);
+			SCX_CALL_OP(SCX_KF_REST, cpu_acquire, cpu_of(rq), NULL);
 		rq->scx.cpu_released = false;
 	}