| Message ID | 1343316846-25860-4-git-send-email-stefano.stabellini@eu.citrix.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
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? > > 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 > > > _______________________________________________ > Xen-devel mailing list > Xen-devel@lists.xen.org > http://lists.xen.org/xen-devel
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 > > > > > > _______________________________________________ > > Xen-devel mailing list > > Xen-devel@lists.xen.org > > http://lists.xen.org/xen-devel
On Fri, Jul 27, 2012 at 10:28:25AM +0100, Ian Campbell wrote: > 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). OK, that makes sense. Stefano can you include that comment in the git commit description and in the sync_bitops.h file please? > > > > > > > > > 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 > > > > > > > > > _______________________________________________ > > > Xen-devel mailing list > > > Xen-devel@lists.xen.org > > > http://lists.xen.org/xen-devel >
On Wed, 1 Aug 2012, Konrad Rzeszutek Wilk wrote: > On Fri, Jul 27, 2012 at 10:28:25AM +0100, Ian Campbell wrote: > > 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). > > OK, that makes sense. Stefano can you include that comment in the git > commit description and in the sync_bitops.h file please? Yep, I'll do that.
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
sync_bitops functions are equivalent to the SMP implementation of the original functions, independently from CONFIG_SMP being defined. 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