On Mon, Aug 06, 2012 at 03:27:07PM +0100, Stefano Stabellini wrote:
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.
Ack from me.
Signed-off-by: Stefano Stabellini stefano.stabellini@eu.citrix.com
arch/arm/include/asm/sync_bitops.h | 27 +++++++++++++++++++++++++++ 1 files changed, 27 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..63479ee --- /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
1.7.2.5