scx_lavd: Switch to scx_bpf_remote_curr()

The new scx_bpf_remote_curr() is safer to use, switch to it
from scx_bpf_cpu_rq() as we only care about it's ->curr anyway.

Signed-off-by: Christian Loehle <[email protected]>

Author: cloehle

scheds/rust/scx_lavd/src/bpf/preempt.bpf.c

@@ -189,11 +189,10 @@ static void ask_cpu_yield_after(struct cpu_ctx *victim_cpuc, u64 new_slice)
 	 * set the victim task's time slice to zero so the victim task yields
 	 * the CPU in the next scheduling point.
 	 */
-	struct rq *victim_rq;
 	struct task_struct *victim_p;
 
-	victim_rq = scx_bpf_cpu_rq(victim_cpuc->cpu_id);
-	if (victim_rq && (victim_p = victim_rq->curr)) {
+	victim_p = scx_bpf_remote_curr(victim_cpuc->cpu_id);
+	if (victim_p) {
 		/*
 		 * Finding a victim is racy, but we do not coordinate. Thus,
 		 * two different CPUs can choose the same victim CPU. We do not
@@ -213,8 +212,10 @@ static void ask_cpu_yield_after(struct cpu_ctx *victim_cpuc, u64 new_slice)
 		 * (SCX_SLICE_DFL, 20 msec).
 		 */
 		u64 old = victim_cpuc->est_stopping_clk;
-		if (!old)
+		if (!old) {
+			bpf_task_release(victim_p);
 			return;
+		}
 
 		/*
 		 * If the new slice is one, this is the last time to be kicked,
@@ -232,6 +233,7 @@ static void ask_cpu_yield_after(struct cpu_ctx *victim_cpuc, u64 new_slice)
 			if (victim_p->scx.slice > new_slice)
 				WRITE_ONCE(victim_p->scx.slice, new_slice);
 		}
+		bpf_task_release(victim_p);
 	}
 }