From 88c805d318822c40a57f2d4a983ad05ab06d35e1 Mon Sep 17 00:00:00 2001
From: Nicolas Pitre <nico@cam.org>
Date: Mon, 19 Dec 2005 22:20:51 +0000
Subject: [PATCH] --- yaml --- r: 15227 b: refs/heads/master c:
 7c612bfd4ed3064fd48a4877a114c8186547367b h: refs/heads/master i:   15225:
 c874d2781a1c5f982c6b3756f4e1f225e0c91c30   15223:
 b88749359afc504a9f26c4450bb7fd8aa1dc2251 v: v3

---
 [refs]                             |  2 +-
 trunk/arch/arm/kernel/entry-armv.S | 49 ++++++++++++++++++++++++++++++
 2 files changed, 50 insertions(+), 1 deletion(-)

diff --git a/[refs] b/[refs]
index 5c5d60e1ae9f..7385ba95f78c 100644
--- a/[refs]
+++ b/[refs]
@@ -1,2 +1,2 @@
 ---
-refs/heads/master: 567bd98017d9c9f2ac1c148ddc78c062e8abd398
+refs/heads/master: 7c612bfd4ed3064fd48a4877a114c8186547367b
diff --git a/trunk/arch/arm/kernel/entry-armv.S b/trunk/arch/arm/kernel/entry-armv.S
index d9fb819bf7cc..2a8d27e18fa7 100644
--- a/trunk/arch/arm/kernel/entry-armv.S
+++ b/trunk/arch/arm/kernel/entry-armv.S
@@ -611,6 +611,47 @@ ENTRY(__switch_to)
 	.globl	__kuser_helper_start
 __kuser_helper_start:
 
+/*
+ * Reference prototype:
+ *
+ *	void __kernel_memory_barrier(void)
+ *
+ * Input:
+ *
+ *	lr = return address
+ *
+ * Output:
+ *
+ *	none
+ *
+ * Clobbered:
+ *
+ *	the Z flag might be lost
+ *
+ * Definition and user space usage example:
+ *
+ *	typedef void (__kernel_dmb_t)(void);
+ *	#define __kernel_dmb (*(__kernel_dmb_t *)0xffff0fa0)
+ *
+ * Apply any needed memory barrier to preserve consistency with data modified
+ * manually and __kuser_cmpxchg usage.
+ *
+ * This could be used as follows:
+ *
+ * #define __kernel_dmb() \
+ *         asm volatile ( "mov r0, #0xffff0fff; mov lr, pc; sub pc, r0, #95" \
+ *	        : : : "lr","cc" )
+ */
+
+__kuser_memory_barrier:				@ 0xffff0fa0
+
+#if __LINUX_ARM_ARCH__ >= 6 && defined(CONFIG_SMP)
+	mcr	p15, 0, r0, c7, c10, 5	@ dmb
+#endif
+	mov	pc, lr
+
+	.align	5
+
 /*
  * Reference prototype:
  *
@@ -642,6 +683,8 @@ __kuser_helper_start:
  * The C flag is also set if *ptr was changed to allow for assembly
  * optimization in the calling code.
  *
+ * Note: this routine already includes memory barriers as needed.
+ *
  * For example, a user space atomic_add implementation could look like this:
  *
  * #define atomic_add(ptr, val) \
@@ -698,10 +741,16 @@ __kuser_cmpxchg:				@ 0xffff0fc0
 
 #else
 
+#ifdef CONFIG_SMP
+	mcr	p15, 0, r0, c7, c10, 5	@ dmb
+#endif
 	ldrex	r3, [r2]
 	subs	r3, r3, r0
 	strexeq	r3, r1, [r2]
 	rsbs	r0, r3, #0
+#ifdef CONFIG_SMP
+	mcr	p15, 0, r0, c7, c10, 5	@ dmb
+#endif
 	mov	pc, lr
 
 #endif