From f983711cf1003cc7e533d6c36b09e322bdcd9622 Mon Sep 17 00:00:00 2001 From: Will Deacon Date: Mon, 30 Apr 2018 13:56:32 +0100 Subject: [PATCH] arm64: cmpwait: Clear event register before arming exclusive monitor [ Upstream commit 1cfc63b5ae60fe7e01773f38132f98d8b13a99a0 ] When waiting for a cacheline to change state in cmpwait, we may immediately wake-up the first time around the outer loop if the event register was already set (for example, because of the event stream). Avoid these spurious wakeups by explicitly clearing the event register before loading the cacheline and setting the exclusive monitor. Signed-off-by: Will Deacon Signed-off-by: Catalin Marinas Signed-off-by: Sasha Levin Signed-off-by: Greg Kroah-Hartman --- arch/arm64/include/asm/cmpxchg.h | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) diff --git a/arch/arm64/include/asm/cmpxchg.h b/arch/arm64/include/asm/cmpxchg.h index 4f5fd2a36e6ec..3b09382815419 100644 --- a/arch/arm64/include/asm/cmpxchg.h +++ b/arch/arm64/include/asm/cmpxchg.h @@ -204,7 +204,9 @@ static inline void __cmpwait_case_##name(volatile void *ptr, \ unsigned long tmp; \ \ asm volatile( \ - " ldxr" #sz "\t%" #w "[tmp], %[v]\n" \ + " sevl\n" \ + " wfe\n" \ + " ldxr" #sz "\t%" #w "[tmp], %[v]\n" \ " eor %" #w "[tmp], %" #w "[tmp], %" #w "[val]\n" \ " cbnz %" #w "[tmp], 1f\n" \ " wfe\n" \ -- 2.47.2