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Date:      Thu, 30 Jul 2015 00:13:20 +0000 (UTC)
From:      Konstantin Belousov <kib@FreeBSD.org>
To:        src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-head@freebsd.org
Subject:   svn commit: r286051 - in head/sys/i386: i386 include
Message-ID:  <201507300013.t6U0DKml017921@repo.freebsd.org>
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Author: kib
Date: Thu Jul 30 00:13:20 2015
New Revision: 286051
URL: https://svnweb.freebsd.org/changeset/base/286051

Log:
  Use private cache line for the locked nop in *mb() on i386.
  
  Suggested by:	alc
  Reviewed by:	alc, bde
  Tested by:	pho
  Sponsored by:	The FreeBSD Foundation
  MFC after:	2 weeks

Modified:
  head/sys/i386/i386/vm_machdep.c
  head/sys/i386/include/atomic.h

Modified: head/sys/i386/i386/vm_machdep.c
==============================================================================
--- head/sys/i386/i386/vm_machdep.c	Wed Jul 29 23:59:17 2015	(r286050)
+++ head/sys/i386/i386/vm_machdep.c	Thu Jul 30 00:13:20 2015	(r286051)
@@ -111,8 +111,8 @@ _Static_assert(OFFSETOF_CURTHREAD == off
     "OFFSETOF_CURTHREAD does not correspond with offset of pc_curthread.");
 _Static_assert(OFFSETOF_CURPCB == offsetof(struct pcpu, pc_curpcb),
     "OFFSETOF_CURPCB does not correspond with offset of pc_curpcb.");
-_Static_assert(OFFSETOF_MONITORBUF == offsetof(struct pcpu, pc_monitorbuf),
-    "OFFSETOF_MONINORBUF does not correspond with offset of pc_monitorbuf.");
+_Static_assert(__OFFSETOF_MONITORBUF == offsetof(struct pcpu, pc_monitorbuf),
+    "__OFFSETOF_MONINORBUF does not correspond with offset of pc_monitorbuf.");
 
 static void	cpu_reset_real(void);
 #ifdef SMP

Modified: head/sys/i386/include/atomic.h
==============================================================================
--- head/sys/i386/include/atomic.h	Wed Jul 29 23:59:17 2015	(r286050)
+++ head/sys/i386/include/atomic.h	Thu Jul 30 00:13:20 2015	(r286051)
@@ -37,9 +37,31 @@
 #include <machine/specialreg.h>
 #endif
 
-#define	mb()	__asm __volatile("lock; addl $0,(%%esp)" : : : "memory", "cc")
-#define	wmb()	__asm __volatile("lock; addl $0,(%%esp)" : : : "memory", "cc")
-#define	rmb()	__asm __volatile("lock; addl $0,(%%esp)" : : : "memory", "cc")
+#ifndef __OFFSETOF_MONITORBUF
+/*
+ * __OFFSETOF_MONITORBUF == __pcpu_offset(pc_monitorbuf).
+ *
+ * The open-coded number is used instead of the symbolic expression to
+ * avoid a dependency on sys/pcpu.h in machine/atomic.h consumers.
+ * An assertion in i386/vm_machdep.c ensures that the value is correct.
+ */
+#define	__OFFSETOF_MONITORBUF	0x180
+
+static __inline void
+__mbk(void)
+{
+
+	__asm __volatile("lock; addl $0,%%fs:%0"
+	    : "+m" (*(u_int *)__OFFSETOF_MONITORBUF) : : "memory", "cc");
+}
+
+static __inline void
+__mbu(void)
+{
+
+	__asm __volatile("lock; addl $0,(%%esp)" : : : "memory", "cc");
+}
+#endif
 
 /*
  * Various simple operations on memory, each of which is atomic in the
@@ -246,40 +268,15 @@ atomic_testandset_int(volatile u_int *p,
  * reordering accesses in a way that violates the semantics of acquire
  * and release.
  */
-#if defined(_KERNEL)
-
-/*
- * OFFSETOF_MONITORBUF == __pcpu_offset(pc_monitorbuf).
- *
- * The open-coded number is used instead of the symbolic expression to
- * avoid a dependency on sys/pcpu.h in machine/atomic.h consumers.
- * An assertion in i386/vm_machdep.c ensures that the value is correct.
- */
-#define	OFFSETOF_MONITORBUF	0x180
 
+#if defined(_KERNEL)
 #if defined(SMP)
-static __inline void
-__storeload_barrier(void)
-{
-
-	__asm __volatile("lock; addl $0,%%fs:%0"
-	    : "+m" (*(u_int *)OFFSETOF_MONITORBUF) : : "memory", "cc");
-}
+#define	__storeload_barrier()	__mbk()
 #else /* _KERNEL && UP */
-static __inline void
-__storeload_barrier(void)
-{
-
-	__compiler_membar();
-}
+#define	__storeload_barrier()	__compiler_membar()
 #endif /* SMP */
 #else /* !_KERNEL */
-static __inline void
-__storeload_barrier(void)
-{
-
-	__asm __volatile("lock; addl $0,(%%esp)" : : : "memory", "cc");
-}
+#define	__storeload_barrier()	__mbu()
 #endif /* _KERNEL*/
 
 #define	ATOMIC_LOAD(TYPE)					\
@@ -776,4 +773,14 @@ u_long	atomic_swap_long(volatile u_long 
 
 #endif /* !WANT_FUNCTIONS */
 
+#if defined(_KERNEL)
+#define	mb()	__mbk()
+#define	wmb()	__mbk()
+#define	rmb()	__mbk()
+#else
+#define	mb()	__mbu()
+#define	wmb()	__mbu()
+#define	rmb()	__mbu()
+#endif
+
 #endif /* !_MACHINE_ATOMIC_H_ */

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