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.stabell...@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 _______________________________________________ linaro-dev mailing list linaro-dev@lists.linaro.org http://lists.linaro.org/mailman/listinfo/linaro-dev
