On Thu, 2012-07-26 at 17:37 +0100, Konrad Rzeszutek Wilk wrote:

On Thu, Jul 26, 2012 at 04:33:46PM +0100, Stefano Stabellini wrote:

quoted

sync_bitops functions are equivalent to the SMP implementation of the
original functions, independently from CONFIG_SMP being defined.

So why can't the code be changed to use that? Is it that
the _set_bit, _clear_bit, etc are not available with !CONFIG_SMP?

_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.

The users are common code and the sync_foo vs foo distinction matters on
some platforms (e.g. x86 where a UP kernel would omit the LOCK prefix
for the normal ones).

quoted

Signed-off-by: Stefano Stabellini <redacted>
---
 arch/arm/include/asm/sync_bitops.h |   17 +++++++++++++++++
 1 files changed, 17 insertions(+), 0 deletions(-)
 create mode 100644 arch/arm/include/asm/sync_bitops.h

diff --git a/arch/arm/include/asm/sync_bitops.h b/arch/arm/include/asm/sync_bitops.h
new file mode 100644
index 0000000..d975092903
--- /dev/null
+++ b/arch/arm/include/asm/sync_bitops.h

@@ -0,0 +1,17 @@
+#ifndef __ASM_SYNC_BITOPS_H__
+#define __ASM_SYNC_BITOPS_H__
+
+#include <asm/bitops.h>
+#include <asm/system.h>
+
+#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

-- 
1.7.2.5


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