x86: drop extra semi-colon in caa_cpu_relax

[urcu.git] / urcu / arch / x86.h

diff --git a/urcu/arch/x86.h b/urcu/arch/x86.h
index 9e5411fd4453ee7033d15e0280fdf9208d8b3f50..ccc4ce8aab5235a9c6209867d3e99c15f62c1fc0 100644 (file)
--- a/urcu/arch/x86.h
+++ b/urcu/arch/x86.h
@@ -32,25 +32,46 @@ extern "C" {
 #define CAA_CACHE_LINE_SIZE    128
 
 #ifdef CONFIG_RCU_HAVE_FENCE
-#define cmm_mb()    asm volatile("mfence":::"memory")
-#define cmm_rmb()   asm volatile("lfence":::"memory")
-#define cmm_wmb()   asm volatile("sfence"::: "memory")
+#define cmm_mb()    __asm__ __volatile__ ("mfence":::"memory")
+
+/*
+ * Define cmm_rmb/cmm_wmb to "strict" barriers that may be needed when
+ * using SSE or working with I/O areas.  cmm_smp_rmb/cmm_smp_wmb are
+ * only compiler barriers, which is enough for general use.
+ */
+#define cmm_rmb()     __asm__ __volatile__ ("lfence":::"memory")
+#define cmm_wmb()     __asm__ __volatile__ ("sfence"::: "memory")
+#define cmm_smp_rmb() cmm_barrier()
+#define cmm_smp_wmb() cmm_barrier()
 #else
 /*
- * Some non-Intel clones support out of order store. cmm_wmb() ceases to be a
- * nop for these.
+ * We leave smp_rmb/smp_wmb as full barriers for processors that do not have
+ * fence instructions.
+ *
+ * An empty cmm_smp_rmb() may not be enough on old PentiumPro multiprocessor
+ * systems, due to an erratum.  The Linux kernel says that "Even distro
+ * kernels should think twice before enabling this", but for now let's
+ * be conservative and leave the full barrier on 32-bit processors.  Also,
+ * IDT WinChip supports weak store ordering, and the kernel may enable it
+ * under our feet; cmm_smp_wmb() ceases to be a nop for these processors.
  */
-#define cmm_mb()    asm volatile("lock; addl $0,0(%%esp)":::"memory")
-#define cmm_rmb()   asm volatile("lock; addl $0,0(%%esp)":::"memory")
-#define cmm_wmb()   asm volatile("lock; addl $0,0(%%esp)"::: "memory")
+#if (CAA_BITS_PER_LONG == 32)
+#define cmm_mb()    __asm__ __volatile__ ("lock; addl $0,0(%%esp)":::"memory")
+#define cmm_rmb()    __asm__ __volatile__ ("lock; addl $0,0(%%esp)":::"memory")
+#define cmm_wmb()    __asm__ __volatile__ ("lock; addl $0,0(%%esp)":::"memory")
+#else
+#define cmm_mb()    __asm__ __volatile__ ("lock; addl $0,0(%%rsp)":::"memory")
+#define cmm_rmb()    __asm__ __volatile__ ("lock; addl $0,0(%%rsp)":::"memory")
+#define cmm_wmb()    __asm__ __volatile__ ("lock; addl $0,0(%%rsp)":::"memory")
+#endif
 #endif
 
-#define caa_cpu_relax()        asm volatile("rep; nop" : : : "memory");
+#define caa_cpu_relax()        __asm__ __volatile__ ("rep; nop" : : : "memory")
 
 #define rdtscll(val)                                                     \
        do {                                                              \
             unsigned int __a, __d;                                       \
-            asm volatile("rdtsc" : "=a" (__a), "=d" (__d));              \
+            __asm__ __volatile__ ("rdtsc" : "=a" (__a), "=d" (__d));     \
             (val) = ((unsigned long long)__a)                            \
                        | (((unsigned long long)__d) << 32);              \
        } while(0)