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:
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).
Signed-off-by: Stefano Stabellini stefano.stabellini@eu.citrix.com
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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