X-Git-Url: https://err.no/cgi-bin/gitweb.cgi?a=blobdiff_plain;f=include%2Fasm-x86%2Fpercpu.h;h=4e91ee1e37aa170140e92814a08232fef4e6dfd4;hb=6d273f8d011c351c9603c1dbfeae2c7458edd30d;hp=912a3a17b9db85958abee1464d58e64d798f5f31;hpb=5806b81ac1c0c52665b91723fd4146a4f86e386b;p=linux-2.6

diff --git a/include/asm-x86/percpu.h b/include/asm-x86/percpu.h
index 912a3a17b9..4e91ee1e37 100644
--- a/include/asm-x86/percpu.h
+++ b/include/asm-x86/percpu.h
@@ -22,6 +22,32 @@
 
 DECLARE_PER_CPU(struct x8664_pda, pda);
 
+/*
+ * These are supposed to be implemented as a single instruction which
+ * operates on the per-cpu data base segment.  x86-64 doesn't have
+ * that yet, so this is a fairly inefficient workaround for the
+ * meantime.  The single instruction is atomic with respect to
+ * preemption and interrupts, so we need to explicitly disable
+ * interrupts here to achieve the same effect.  However, because it
+ * can be used from within interrupt-disable/enable, we can't actually
+ * disable interrupts; disabling preemption is enough.
+ */
+#define x86_read_percpu(var)						\
+	({								\
+		typeof(per_cpu_var(var)) __tmp;				\
+		preempt_disable();					\
+		__tmp = __get_cpu_var(var);				\
+		preempt_enable();					\
+		__tmp;							\
+	})
+
+#define x86_write_percpu(var, val)					\
+	do {								\
+		preempt_disable();					\
+		__get_cpu_var(var) = (val);				\
+		preempt_enable();					\
+	} while(0)
+
 #else /* CONFIG_X86_64 */
 
 #ifdef __ASSEMBLY__