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.stabell...@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 > > > > > > _______________________________________________ > > Xen-devel mailing list > > xen-de...@lists.xen.org > > http://lists.xen.org/xen-devel _______________________________________________ linaro-dev mailing list linaro-dev@lists.linaro.org http://lists.linaro.org/mailman/listinfo/linaro-dev
