From: David Vrabel <david.vrabel@citrix.com>
Date: Fri, 8 May 2015 08:59:44 +0000 (+0200)
Subject: arm: provide arch_fetch_and_add()
X-Git-Tag: archive/raspbian/4.8.0-1+rpi1~1^2~3320
X-Git-Url: https://dgit.raspbian.org/%22http://www.example.com/cgi/%22/%22http:/www.example.com/cgi/%22?a=commitdiff_plain;h=f9cc3cd9b4de58cf032c8624406384c172937e57;p=xen.git

arm: provide arch_fetch_and_add()

arch_fetch_and_add() atomically adds a value and returns the previous
value.

This generic arm implementation uses the GCC __sync_fetch_and_add()
builtin.  This builtin resulted in suitable inlined asm for GCC 4.8.3
(arm64) and GCC 4.6.3 (arm32).

This is needed to implement ticket locks.

Signed-off-by: David Vrabel <david.vrabel@citrix.com>
Acked-by: Ian Campbell <ian.campbell@citrix.com>
---

diff --git a/xen/include/asm-arm/system.h b/xen/include/asm-arm/system.h
index ce3d38ac0c..2eb96e8769 100644
--- a/xen/include/asm-arm/system.h
+++ b/xen/include/asm-arm/system.h
@@ -51,6 +51,8 @@
 # error "unknown ARM variant"
 #endif
 
+#define arch_fetch_and_add(x, v) __sync_fetch_and_add(x, v)
+
 extern struct vcpu *__context_switch(struct vcpu *prev, struct vcpu *next);
 
 #endif