From ea818ea8340c13742a4f41e6077f732291aea4bc Mon Sep 17 00:00:00 2001 From: Rich Felker Date: Mon, 25 Aug 2014 15:43:40 -0400 Subject: add working a_spin() atomic for non-x86 targets conceptually, a_spin needs to be at least a compiler barrier, so the compiler will not optimize out loops (and the load on each iteration) while spinning. it should also be a memory barrier, or the spinning thread might keep spinning without noticing stores from other threads, thus delaying for longer than it should. ideally, an optimal a_spin implementation that avoids unnecessary cache/memory contention should be chosen for each arch, but for now, the easiest thing is to perform a useless a_cas on the calling thread's stack. --- arch/sh/atomic.h | 1 + 1 file changed, 1 insertion(+) (limited to 'arch/sh/atomic.h') diff --git a/arch/sh/atomic.h b/arch/sh/atomic.h index 93ab54fe..b95bbffc 100644 --- a/arch/sh/atomic.h +++ b/arch/sh/atomic.h @@ -53,6 +53,7 @@ static inline void a_dec(volatile int *x) static inline void a_spin() { + a_cas(&(int){0}, 0, 0); } static inline void a_crash() -- cgit v1.2.1