From db3bf8271bd6afe732256b98e86fe38612cb5ff9 Mon Sep 17 00:00:00 2001
From: cinap_lenrek <cinap_lenrek@felloff.net>
Date: Fri, 10 May 2019 14:05:04 +0200
Subject: [PATCH] bcm64: use exclusive monitor on nrdy to wake up idlehands()

when the exclusive monitor is cleared, a event is generated
which we can use to wake up idlehands. that way we do not
need to wait for the next timer interrupt until a cpu takes
work from the run queue.
---
 sys/src/9/bcm64/l.s | 11 +++++++----
 1 file changed, 7 insertions(+), 4 deletions(-)

diff --git a/sys/src/9/bcm64/l.s b/sys/src/9/bcm64/l.s
index 4e64773f7..69e9c3924 100644
--- a/sys/src/9/bcm64/l.s
+++ b/sys/src/9/bcm64/l.s
@@ -293,10 +293,13 @@ TEXT splx(SB), 1, $-4
 
 TEXT idlehands(SB), 1, $-4
 	DMB	$ISH
-	MOVW	nrdy(SB), R0
-	CBNZ	R0, _ready
-	WFI
-_ready:
+	MOV	$nrdy(SB), R1
+	LDXRW	(R1), R0
+	CBZ	R0, _goodnight
+	CLREX
+	SEVL
+_goodnight:
+	WFE
 	RETURN
 
 TEXT cycles(SB), 1, $-4