From 11ea0b8f38c408a0d31cca9e8df09ceae018ba1b Mon Sep 17 00:00:00 2001 From: kib Date: Fri, 8 Jun 2018 18:32:26 +0000 Subject: [PATCH] Restore release semantic for the old thread unlock on arm64. With the introduction of pmap_switch(), the DSB instruction on the address map switch is not necessary executed, which is fixed by changing the unlock store to release. Also remove comment which documented pre-pmap_switch() code. Reviewed by: andrew Sponsored by: The FreeBSD Foundation MFC after: 1 week --- sys/arm64/arm64/swtch.S | 5 ++--- 1 file changed, 2 insertions(+), 3 deletions(-) diff --git a/sys/arm64/arm64/swtch.S b/sys/arm64/arm64/swtch.S index c9843303b1d3..4c2c3aca5833 100644 --- a/sys/arm64/arm64/swtch.S +++ b/sys/arm64/arm64/swtch.S @@ -165,10 +165,9 @@ ENTRY(cpu_switch) mov x0, x19 /* - * Release the old thread. This doesn't need to be a store-release - * as the above dsb instruction will provide release semantics. + * Release the old thread. */ - str x2, [x0, #TD_LOCK] + stlr x2, [x0, #TD_LOCK] #if defined(SCHED_ULE) && defined(SMP) /* Spin if TD_LOCK points to a blocked_lock */ ldr x2, =_C_LABEL(blocked_lock)