From mboxrd@z Thu Jan 1 00:00:00 1970 From: pbonzini@redhat.com (Paolo Bonzini) Date: Thu, 22 Sep 2011 10:42:52 +0200 Subject: [ltt-dev] [PATCH v2] cmm: provide lightweight smp_rmb/smp_wmb on PPC In-Reply-To: <20110921234242.GG2394@linux.vnet.ibm.com> References: <20110921234242.GG2394@linux.vnet.ibm.com> Message-ID: <1316680972-15081-1-git-send-email-pbonzini@redhat.com> lwsync orders loads in cacheable memory with respect to other loads, and stores in cacheable memory with respect to other stores. Use it to implement smp_rmb/smp_wmb. The heavy-weight sync is still used for the "full" rmb/wmb operations, as well as for smp_mb. Signed-off-by: Paolo Bonzini --- urcu/arch/ppc.h | 10 +++++++++- 1 files changed, 9 insertions(+), 1 deletions(-) diff --git a/urcu/arch/ppc.h b/urcu/arch/ppc.h index a03d688..05f7db6 100644 --- a/urcu/arch/ppc.h +++ b/urcu/arch/ppc.h @@ -32,7 +32,15 @@ extern "C" { /* Include size of POWER5+ L3 cache lines: 256 bytes */ #define CAA_CACHE_LINE_SIZE 256 -#define cmm_mb() asm volatile("sync":::"memory") +#define cmm_mb() asm volatile("sync":::"memory") + +/* lwsync does not preserve ordering of cacheable vs. non-cacheable + * accesses, but it is good when MMIO is not in use. An eieio+lwsync + * pair is also not enough for rmb, because it will order cacheable + * and non-cacheable memory operations separately---i.e. not the latter + * against the former. */ +#define cmm_smp_rmb() asm volatile("lwsync":::"memory") +#define cmm_smp_wmb() asm volatile("lwsync":::"memory") #define mftbl() \ ({ \ -- 1.7.6