From: David S. Miller Date: Fri, 6 Nov 2009 04:24:33 +0000 (-0800) Subject: sparc64: Add a comment about why we only use certain memory barriers these days. X-Git-Tag: firefly_0821_release~11830^2~9 X-Git-Url: http://demsky.eecs.uci.edu/git/?a=commitdiff_plain;h=4eb0c00b6221f28b8988df37c9cb1bc5a2b91b39;p=firefly-linux-kernel-4.4.55.git sparc64: Add a comment about why we only use certain memory barriers these days. Based upon feedback from Mathieu Desnoyers. Signed-off-by: David S. Miller --- diff --git a/arch/sparc/include/asm/system_64.h b/arch/sparc/include/asm/system_64.h index 25e848f0cad7..d47a98e66972 100644 --- a/arch/sparc/include/asm/system_64.h +++ b/arch/sparc/include/asm/system_64.h @@ -63,6 +63,10 @@ do { __asm__ __volatile__("ba,pt %%xcc, 1f\n\t" \ : : : "memory"); \ } while (0) +/* The kernel always executes in TSO memory model these days, + * and furthermore most sparc64 chips implement more stringent + * memory ordering than required by the specifications. + */ #define mb() membar_safe("#StoreLoad") #define rmb() __asm__ __volatile__("":::"memory") #define wmb() __asm__ __volatile__("":::"memory")