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authorChris Wright <chrisw@sous-sol.org>2006-09-25 23:32:23 -0700
committerLinus Torvalds <torvalds@g5.osdl.org>2006-09-26 08:48:55 -0700
commit027a8c7e6067a1bcdef6775d1b1c08729dfbae51 (patch)
tree8c791bb8820d6c0734aded634a045369dd3347cc /include/asm-i386/system.h
parent05f4a3ec94281347e05c81eafefcfe5ea545c94c (diff)
[PATCH] x86: implement always-locked bit ops, for memory shared with an SMP hypervisor
Add "always lock'd" implementations of set_bit, clear_bit and change_bit and the corresponding test_and_ functions. Also add "always lock'd" implementation of cmpxchg. These give guaranteed strong synchronisation and are required for non-SMP kernels running on an SMP hypervisor. Signed-off-by: Ian Pratt <ian.pratt@xensource.com> Signed-off-by: Christian Limpach <Christian.Limpach@cl.cam.ac.uk> Signed-off-by: Chris Wright <chrisw@sous-sol.org> Signed-off-by: Jeremy Fitzhardinge <jeremy@xensource.com> Cc: Christoph Lameter <clameter@sgi.com> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Diffstat (limited to 'include/asm-i386/system.h')
-rw-r--r--include/asm-i386/system.h36
1 files changed, 36 insertions, 0 deletions
diff --git a/include/asm-i386/system.h b/include/asm-i386/system.h
index 098bcee94e3..a6dabbcd6e6 100644
--- a/include/asm-i386/system.h
+++ b/include/asm-i386/system.h
@@ -267,6 +267,9 @@ static inline unsigned long __xchg(unsigned long x, volatile void * ptr, int siz
#define cmpxchg(ptr,o,n)\
((__typeof__(*(ptr)))__cmpxchg((ptr),(unsigned long)(o),\
(unsigned long)(n),sizeof(*(ptr))))
+#define sync_cmpxchg(ptr,o,n)\
+ ((__typeof__(*(ptr)))__sync_cmpxchg((ptr),(unsigned long)(o),\
+ (unsigned long)(n),sizeof(*(ptr))))
#endif
static inline unsigned long __cmpxchg(volatile void *ptr, unsigned long old,
@@ -296,6 +299,39 @@ static inline unsigned long __cmpxchg(volatile void *ptr, unsigned long old,
return old;
}
+/*
+ * Always use locked operations when touching memory shared with a
+ * hypervisor, since the system may be SMP even if the guest kernel
+ * isn't.
+ */
+static inline unsigned long __sync_cmpxchg(volatile void *ptr,
+ unsigned long old,
+ unsigned long new, int size)
+{
+ unsigned long prev;
+ switch (size) {
+ case 1:
+ __asm__ __volatile__("lock; cmpxchgb %b1,%2"
+ : "=a"(prev)
+ : "q"(new), "m"(*__xg(ptr)), "0"(old)
+ : "memory");
+ return prev;
+ case 2:
+ __asm__ __volatile__("lock; cmpxchgw %w1,%2"
+ : "=a"(prev)
+ : "r"(new), "m"(*__xg(ptr)), "0"(old)
+ : "memory");
+ return prev;
+ case 4:
+ __asm__ __volatile__("lock; cmpxchgl %1,%2"
+ : "=a"(prev)
+ : "r"(new), "m"(*__xg(ptr)), "0"(old)
+ : "memory");
+ return prev;
+ }
+ return old;
+}
+
#ifndef CONFIG_X86_CMPXCHG
/*
* Building a kernel capable running on 80386. It may be necessary to