1 files changed, 27 insertions, 0 deletions

diff --git a/arch/arm/include/asm/sync_bitops.h b/arch/arm/include/asm/sync_bitops.h
new file mode 100644
index 000000000000..63479eecbf76
--- /dev/null
+++ b/arch/arm/include/asm/sync_bitops.h
@@ -0,0 +1,27 @@
+#ifndef __ASM_SYNC_BITOPS_H__
+#define __ASM_SYNC_BITOPS_H__
+
+#include <asm/bitops.h>
+#include <asm/system.h>
+
+/* sync_bitops functions are equivalent to the SMP implementation of the
+ * original functions, independently from CONFIG_SMP being defined.
+ *
+ * We need them because _set_bit etc are not SMP safe if !CONFIG_SMP. But
+ * under Xen you might be communicating with a completely external entity
+ * who might be on another CPU (e.g. two uniprocessor guests communicating
+ * via event channels and grant tables). So we need a variant of the bit
+ * ops which are SMP safe even on a UP kernel.
+ */
+
+#define sync_set_bit(nr, p)             _set_bit(nr, p)
+#define sync_clear_bit(nr, p)           _clear_bit(nr, p)
+#define sync_change_bit(nr, p)          _change_bit(nr, p)
+#define sync_test_and_set_bit(nr, p)    _test_and_set_bit(nr, p)
+#define sync_test_and_clear_bit(nr, p)  _test_and_clear_bit(nr, p)
+#define sync_test_and_change_bit(nr, p) _test_and_change_bit(nr, p)
+#define sync_test_bit(nr, addr)         test_bit(nr, addr)
+#define sync_cmpxchg                    cmpxchg
+
+
+#endif