Re: [PATCH v2 15/32] powerpc: define __smp_xxx
Hi Michael,
On Thu, Dec 31, 2015 at 09:07:42PM +0200, Michael S. Tsirkin wrote:
> This defines __smp_xxx barriers for powerpc
> for use by virtualization.
>
> smp_xxx barriers are removed as they are
> defined correctly by asm-generic/barriers.h
>
> This reduces the amount of arch-specific boiler-plate code.
>
> Signed-off-by: Michael S. Tsirkin
> Acked-by: Arnd Bergmann
> ---
> arch/powerpc/include/asm/barrier.h | 24
> 1 file changed, 8 insertions(+), 16 deletions(-)
>
> diff --git a/arch/powerpc/include/asm/barrier.h
> b/arch/powerpc/include/asm/barrier.h
> index 980ad0c..c0deafc 100644
> --- a/arch/powerpc/include/asm/barrier.h
> +++ b/arch/powerpc/include/asm/barrier.h
> @@ -44,19 +44,11 @@
> #define dma_rmb()__lwsync()
> #define dma_wmb()__asm__ __volatile__ (stringify_in_c(SMPWMB) : :
> :"memory")
>
> -#ifdef CONFIG_SMP
> -#define smp_lwsync() __lwsync()
> +#define __smp_lwsync() __lwsync()
>
so __smp_lwsync() is always mapped to lwsync, right?
> -#define smp_mb() mb()
> -#define smp_rmb()__lwsync()
> -#define smp_wmb()__asm__ __volatile__ (stringify_in_c(SMPWMB) : :
> :"memory")
> -#else
> -#define smp_lwsync() barrier()
> -
> -#define smp_mb() barrier()
> -#define smp_rmb()barrier()
> -#define smp_wmb()barrier()
> -#endif /* CONFIG_SMP */
> +#define __smp_mb() mb()
> +#define __smp_rmb() __lwsync()
> +#define __smp_wmb() __asm__ __volatile__ (stringify_in_c(SMPWMB) : :
> :"memory")
>
> /*
> * This is a barrier which prevents following instructions from being
> @@ -67,18 +59,18 @@
> #define data_barrier(x) \
> asm volatile("twi 0,%0,0; isync" : : "r" (x) : "memory");
>
> -#define smp_store_release(p, v)
> \
> +#define __smp_store_release(p, v)
> \
> do { \
> compiletime_assert_atomic_type(*p); \
> - smp_lwsync(); \
> + __smp_lwsync(); \
, therefore this will emit an lwsync no matter SMP or UP.
Another thing is that smp_lwsync() may have a third user(other than
smp_load_acquire() and smp_store_release()):
http://article.gmane.org/gmane.linux.ports.ppc.embedded/89877
I'm OK to change my patch accordingly, but do we really want
smp_lwsync() get involved in this cleanup? If I understand you
correctly, this cleanup focuses on external API like smp_{r,w,}mb(),
while smp_lwsync() is internal to PPC.
Regards,
Boqun
> WRITE_ONCE(*p, v); \
> } while (0)
>
> -#define smp_load_acquire(p) \
> +#define __smp_load_acquire(p)
> \
> ({ \
> typeof(*p) ___p1 = READ_ONCE(*p); \
> compiletime_assert_atomic_type(*p); \
> - smp_lwsync(); \
> + __smp_lwsync(); \
> ___p1; \
> })
>
> --
> MST
>
> --
> To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
> the body of a message to majord...@vger.kernel.org
> More majordomo info at http://vger.kernel.org/majordomo-info.html
> Please read the FAQ at http://www.tux.org/lkml/
--
To unsubscribe from this list: send the line "unsubscribe linux-metag" in
the body of a message to majord...@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Re: [PATCH v2 15/32] powerpc: define __smp_xxx
On Tue, Jan 05, 2016 at 10:51:17AM +0200, Michael S. Tsirkin wrote:
> On Tue, Jan 05, 2016 at 09:36:55AM +0800, Boqun Feng wrote:
> > Hi Michael,
> >
> > On Thu, Dec 31, 2015 at 09:07:42PM +0200, Michael S. Tsirkin wrote:
> > > This defines __smp_xxx barriers for powerpc
> > > for use by virtualization.
> > >
> > > smp_xxx barriers are removed as they are
> > > defined correctly by asm-generic/barriers.h
>
> I think this is the part that was missed in review.
>
Yes, I realized my mistake after reread the series. But smp_lwsync() is
not defined in asm-generic/barriers.h, right?
> > > This reduces the amount of arch-specific boiler-plate code.
> > >
> > > Signed-off-by: Michael S. Tsirkin
> > > Acked-by: Arnd Bergmann
> > > ---
> > > arch/powerpc/include/asm/barrier.h | 24
> > > 1 file changed, 8 insertions(+), 16 deletions(-)
> > >
> > > diff --git a/arch/powerpc/include/asm/barrier.h
> > > b/arch/powerpc/include/asm/barrier.h
> > > index 980ad0c..c0deafc 100644
> > > --- a/arch/powerpc/include/asm/barrier.h
> > > +++ b/arch/powerpc/include/asm/barrier.h
> > > @@ -44,19 +44,11 @@
> > > #define dma_rmb()__lwsync()
> > > #define dma_wmb()__asm__ __volatile__ (stringify_in_c(SMPWMB) :
> > > : :"memory")
> > >
> > > -#ifdef CONFIG_SMP
> > > -#define smp_lwsync() __lwsync()
> > > +#define __smp_lwsync() __lwsync()
> > >
> >
> > so __smp_lwsync() is always mapped to lwsync, right?
>
> Yes.
>
> > > -#define smp_mb() mb()
> > > -#define smp_rmb()__lwsync()
> > > -#define smp_wmb()__asm__ __volatile__ (stringify_in_c(SMPWMB) :
> > > : :"memory")
> > > -#else
> > > -#define smp_lwsync() barrier()
> > > -
> > > -#define smp_mb() barrier()
> > > -#define smp_rmb()barrier()
> > > -#define smp_wmb()barrier()
> > > -#endif /* CONFIG_SMP */
> > > +#define __smp_mb() mb()
> > > +#define __smp_rmb() __lwsync()
> > > +#define __smp_wmb() __asm__ __volatile__ (stringify_in_c(SMPWMB) :
> > > : :"memory")
> > >
> > > /*
> > > * This is a barrier which prevents following instructions from being
> > > @@ -67,18 +59,18 @@
> > > #define data_barrier(x) \
> > > asm volatile("twi 0,%0,0; isync" : : "r" (x) : "memory");
> > >
> > > -#define smp_store_release(p, v)
> > > \
> > > +#define __smp_store_release(p, v)
> > > \
> > > do {
> > > \
> > > compiletime_assert_atomic_type(*p); \
> > > - smp_lwsync(); \
> > > + __smp_lwsync(); \
> >
> > , therefore this will emit an lwsync no matter SMP or UP.
>
> Absolutely. But smp_store_release (without __) will not.
>
> Please note I did test this: for ppc code before and after
> this patch generates exactly the same binary on SMP and UP.
>
Yes, you're right, sorry for my mistake...
>
> > Another thing is that smp_lwsync() may have a third user(other than
> > smp_load_acquire() and smp_store_release()):
> >
> > http://article.gmane.org/gmane.linux.ports.ppc.embedded/89877
> >
> > I'm OK to change my patch accordingly, but do we really want
> > smp_lwsync() get involved in this cleanup? If I understand you
> > correctly, this cleanup focuses on external API like smp_{r,w,}mb(),
> > while smp_lwsync() is internal to PPC.
> >
> > Regards,
> > Boqun
>
> I think you missed the leading ___ :)
>
What I mean here was smp_lwsync() was originally internal to PPC, but
never mind ;-)
> smp_store_release is external and it needs __smp_lwsync as
> defined here.
>
> I can duplicate some code and have smp_lwsync *not* call __smp_lwsync
You mean bringing smp_lwsync() back? because I haven't seen you defining
in asm-generic/barriers.h in previous patches and you just delete it in
this patch.
> but why do this? Still, if you prefer it this way,
> please let me know.
>
I think deleting smp_lwsync() is fine, though I need to change atomic
variants patches on PPC because of it ;-/
Regards,
Boqun
> > >
Re: [PATCH v2 15/32] powerpc: define __smp_xxx
On Tue, Jan 05, 2016 at 06:16:48PM +0200, Michael S. Tsirkin wrote:
[snip]
> > > > Another thing is that smp_lwsync() may have a third user(other than
> > > > smp_load_acquire() and smp_store_release()):
> > > >
> > > > http://article.gmane.org/gmane.linux.ports.ppc.embedded/89877
> > > >
> > > > I'm OK to change my patch accordingly, but do we really want
> > > > smp_lwsync() get involved in this cleanup? If I understand you
> > > > correctly, this cleanup focuses on external API like smp_{r,w,}mb(),
> > > > while smp_lwsync() is internal to PPC.
> > > >
> > > > Regards,
> > > > Boqun
> > >
> > > I think you missed the leading ___ :)
> > >
> >
> > What I mean here was smp_lwsync() was originally internal to PPC, but
> > never mind ;-)
> >
> > > smp_store_release is external and it needs __smp_lwsync as
> > > defined here.
> > >
> > > I can duplicate some code and have smp_lwsync *not* call __smp_lwsync
> >
> > You mean bringing smp_lwsync() back? because I haven't seen you defining
> > in asm-generic/barriers.h in previous patches and you just delete it in
> > this patch.
> >
> > > but why do this? Still, if you prefer it this way,
> > > please let me know.
> > >
> >
> > I think deleting smp_lwsync() is fine, though I need to change atomic
> > variants patches on PPC because of it ;-/
> >
> > Regards,
> > Boqun
>
> Sorry, I don't understand - why do you have to do anything?
> I changed all users of smp_lwsync so they
> use __smp_lwsync on SMP and barrier() on !SMP.
>
> This is exactly the current behaviour, I also tested that
> generated code does not change at all.
>
> Is there a patch in your tree that conflicts with this?
>
Because in a patchset which implements atomic relaxed/acquire/release
variants on PPC I use smp_lwsync(), this makes it have another user,
please see this mail:
http://article.gmane.org/gmane.linux.ports.ppc.embedded/89877
in definition of PPC's __atomic_op_release().
But I think removing smp_lwsync() is a good idea and actually I think we
can go further to remove __smp_lwsync() and let __smp_load_acquire and
__smp_store_release call __lwsync() directly, but that is another thing.
Anyway, I will modify my patch.
Regards,
Boqun
>
> > > > > WRITE_ONCE(*p, v);
> > > > > \
> > > > > } while (0)
> > > > >
> > > > > -#define smp_load_acquire(p)
> > > > > \
> > > > > +#define __smp_load_acquire(p)
> > > > > \
> > > > > ({
> > > > > \
> > > > > typeof(*p) ___p1 = READ_ONCE(*p);
> > > > > \
> > > > > compiletime_assert_atomic_type(*p);
> > > > > \
> > > > > - smp_lwsync();
> > > > > \
> > > > > + __smp_lwsync();
> > > > > \
> > > > > ___p1;
> > > > > \
> > > > > })
> > > > >
> > > > > --
> > > > > MST
> > > > >
> > > > > --
> > > > > To unsubscribe from this list: send the line "unsubscribe
> > > > > linux-kernel" in
> > > > > the body of a message to majord...@vger.kernel.org
> > > > > More majordomo info at http://vger.kernel.org/majordomo-info.html
> > > > > Please read the FAQ at http://www.tux.org/lkml/
--
To unsubscribe from this list: send the line "unsubscribe linux-metag" in
the body of a message to majord...@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Re: [PATCH v2 15/32] powerpc: define __smp_xxx
On Wed, Jan 06, 2016 at 10:23:51PM +0200, Michael S. Tsirkin wrote: [...] > > > > > > Sorry, I don't understand - why do you have to do anything? > > > I changed all users of smp_lwsync so they > > > use __smp_lwsync on SMP and barrier() on !SMP. > > > > > > This is exactly the current behaviour, I also tested that > > > generated code does not change at all. > > > > > > Is there a patch in your tree that conflicts with this? > > > > > > > Because in a patchset which implements atomic relaxed/acquire/release > > variants on PPC I use smp_lwsync(), this makes it have another user, > > please see this mail: > > > > http://article.gmane.org/gmane.linux.ports.ppc.embedded/89877 > > > > in definition of PPC's __atomic_op_release(). > > > > > > But I think removing smp_lwsync() is a good idea and actually I think we > > can go further to remove __smp_lwsync() and let __smp_load_acquire and > > __smp_store_release call __lwsync() directly, but that is another thing. > > > > Anyway, I will modify my patch. > > > > Regards, > > Boqun > > > Thanks! > Could you send an ack then please? > Sure, if you need one from me, feel free to add my ack for this patch: Acked-by: Boqun Feng Regards, Boqun signature.asc Description: PGP signature
