[Xen-devel] [PATCHv3 2/4] arm: provide xadd()

[David Vrabel <david.vrabel@xxxxxxxxxx>]

xadd() atomically adds a value and returns the previous value.  This
is needed to implement ticket locks.

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).

Signed-off-by: David Vrabel <david.vrabel@xxxxxxxxxx>
Acked-by: Ian Campbell <ian.campbell@xxxxxxxxxx>
---
 xen/include/asm-arm/system.h |    2 ++
 1 file changed, 2 insertions(+)

diff --git a/xen/include/asm-arm/system.h b/xen/include/asm-arm/system.h
index ce3d38a..367af1d 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 xadd(x, v) __sync_fetch_and_add(x, v)
+
 extern struct vcpu *__context_switch(struct vcpu *prev, struct vcpu *next);
 
 #endif
-- 
1.7.10.4


_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxx
http://lists.xen.org/xen-devel