From: "Michael S. Tsirkin" <mst@redhat.com>
To: Boqun Feng <boqun.feng@gmail.com>
Cc: linux-kernel@vger.kernel.org,
Peter Zijlstra <peterz@infradead.org>,
Arnd Bergmann <arnd@arndb.de>,
linux-arch@vger.kernel.org,
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virtualization@lists.linux-foundation.org,
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Thomas Gleixner <tglx@linutronix.de>, Ingo Molnar <mingo@elte.hu>,
"H. Peter Anvin" <hpa@zytor.com>,
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Benjamin Herrenschmidt <benh@kernel.crashing.org>,
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Ingo Molnar <mingo@kernel.org>,
Davidlohr Bueso <dave@stgolabs.net>,
Andrey Konovalov <andreyknvl@google.com>,
"Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
Subject: Re: [PATCH v2 15/32] powerpc: define __smp_xxx
Date: Wed, 6 Jan 2016 22:23:51 +0200 [thread overview]
Message-ID: <20160106222337-mutt-send-email-mst@redhat.com> (raw)
In-Reply-To: <20160106015152.GA14605@fixme-laptop.cn.ibm.com>
On Wed, Jan 06, 2016 at 09:51:52AM +0800, Boqun Feng wrote:
> 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
Thanks!
Could you send an ack then please?
> >
> > > > > > 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 majordomo@vger.kernel.org
> > > > > > More majordomo info at http://vger.kernel.org/majordomo-info.html
> > > > > > Please read the FAQ at http://www.tux.org/lkml/
next prev parent reply other threads:[~2016-01-06 20:24 UTC|newest]
Thread overview: 106+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-12-31 19:05 [PATCH v2 00/34] arch: barrier cleanup + barriers for virt Michael S. Tsirkin
2015-12-31 19:05 ` [PATCH v2 01/32] lcoking/barriers, arch: Use smp barriers in smp_store_release() Michael S. Tsirkin
2015-12-31 19:05 ` [PATCH v2 02/32] asm-generic: guard smp_store_release/load_acquire Michael S. Tsirkin
2015-12-31 19:06 ` [PATCH v2 03/32] ia64: rename nop->iosapic_nop Michael S. Tsirkin
2015-12-31 19:06 ` [PATCH v2 04/32] ia64: reuse asm-generic/barrier.h Michael S. Tsirkin
2015-12-31 19:06 ` [PATCH v2 05/32] powerpc: " Michael S. Tsirkin
2015-12-31 19:06 ` [PATCH v2 06/32] s390: " Michael S. Tsirkin
2016-01-04 13:20 ` Peter Zijlstra
2016-01-04 15:03 ` Martin Schwidefsky
2016-01-04 20:42 ` Michael S. Tsirkin
2016-01-05 8:03 ` Martin Schwidefsky
2016-01-04 20:34 ` Michael S. Tsirkin
2015-12-31 19:06 ` [PATCH v2 07/32] sparc: " Michael S. Tsirkin
2015-12-31 19:43 ` David Miller
2015-12-31 19:06 ` [PATCH v2 08/32] arm: " Michael S. Tsirkin
2016-01-02 11:20 ` Russell King - ARM Linux
2015-12-31 19:06 ` [PATCH v2 09/32] arm64: " Michael S. Tsirkin
2015-12-31 19:07 ` [PATCH v2 10/32] metag: " Michael S. Tsirkin
2016-01-04 23:24 ` James Hogan
2015-12-31 19:07 ` [PATCH v2 11/32] mips: " Michael S. Tsirkin
2016-01-04 13:26 ` Peter Zijlstra
2015-12-31 19:07 ` [PATCH v2 12/32] x86/um: " Michael S. Tsirkin
2016-01-05 23:12 ` Richard Weinberger
2015-12-31 19:07 ` [PATCH v2 13/32] x86: " Michael S. Tsirkin
2015-12-31 19:07 ` [PATCH v2 14/32] asm-generic: add __smp_xxx wrappers Michael S. Tsirkin
2015-12-31 19:07 ` [PATCH v2 15/32] powerpc: define __smp_xxx Michael S. Tsirkin
2016-01-05 1:36 ` Boqun Feng
2016-01-05 8:51 ` Michael S. Tsirkin
2016-01-05 9:53 ` Boqun Feng
2016-01-05 16:16 ` Michael S. Tsirkin
2016-01-06 1:51 ` Boqun Feng
2016-01-06 20:23 ` Michael S. Tsirkin [this message]
2016-01-07 0:43 ` Boqun Feng
2015-12-31 19:07 ` [PATCH v2 16/32] arm64: " Michael S. Tsirkin
2015-12-31 19:07 ` [PATCH v2 17/32] arm: " Michael S. Tsirkin
2016-01-02 11:24 ` Russell King - ARM Linux
2016-01-03 9:12 ` Michael S. Tsirkin
2016-01-04 13:36 ` Peter Zijlstra
2016-01-04 13:54 ` Peter Zijlstra
2016-01-04 13:59 ` Russell King - ARM Linux
2016-01-05 14:38 ` Michael S. Tsirkin
2016-01-04 20:39 ` Michael S. Tsirkin
2016-01-04 20:12 ` Michael S. Tsirkin
2015-12-31 19:08 ` [PATCH v2 18/32] blackfin: " Michael S. Tsirkin
2015-12-31 19:08 ` [PATCH v2 19/32] ia64: " Michael S. Tsirkin
2015-12-31 19:08 ` [PATCH v2 20/32] metag: " Michael S. Tsirkin
2016-01-04 13:41 ` Peter Zijlstra
2016-01-04 15:25 ` James Hogan
2016-01-04 15:30 ` Peter Zijlstra
2016-01-04 16:04 ` James Hogan
2016-01-05 0:09 ` James Hogan
2016-01-11 11:10 ` Michael S. Tsirkin
2015-12-31 19:08 ` [PATCH v2 21/32] mips: " Michael S. Tsirkin
2015-12-31 19:08 ` [PATCH v2 22/32] s390: " Michael S. Tsirkin
2016-01-04 13:45 ` Peter Zijlstra
2016-01-04 20:18 ` Michael S. Tsirkin
2016-01-05 8:13 ` Martin Schwidefsky
2016-01-05 9:30 ` Michael S. Tsirkin
2016-01-05 12:08 ` Martin Schwidefsky
2016-01-05 13:04 ` Michael S. Tsirkin
2016-01-05 14:21 ` Martin Schwidefsky
2016-01-05 15:39 ` Christian Borntraeger
2016-01-05 16:04 ` Michael S. Tsirkin
2015-12-31 19:08 ` [PATCH v2 23/32] sh: define __smp_xxx, fix smp_store_mb for !SMP Michael S. Tsirkin
2015-12-31 19:08 ` [PATCH v2 24/32] sparc: define __smp_xxx Michael S. Tsirkin
2015-12-31 19:44 ` David Miller
2015-12-31 19:09 ` [PATCH v2 25/32] tile: " Michael S. Tsirkin
2015-12-31 19:09 ` [PATCH v2 26/32] xtensa: " Michael S. Tsirkin
2015-12-31 19:09 ` [PATCH v2 27/32] x86: " Michael S. Tsirkin
2015-12-31 19:09 ` [PATCH v2 28/32] asm-generic: implement virt_xxx memory barriers Michael S. Tsirkin
2015-12-31 19:09 ` [PATCH v2 29/32] Revert "virtio_ring: Update weak barriers to use dma_wmb/rmb" Michael S. Tsirkin
2015-12-31 19:09 ` [PATCH v2 31/32] sh: support a 2-byte smp_store_mb Michael S. Tsirkin
2016-01-04 14:05 ` Peter Zijlstra
2016-01-05 23:27 ` Rich Felker
2016-01-06 11:19 ` Michael S. Tsirkin
2016-01-06 11:40 ` Peter Zijlstra
2016-01-06 11:52 ` Michael S. Tsirkin
2016-01-06 14:32 ` Peter Zijlstra
2016-01-06 15:42 ` Rob Landley
2016-01-06 16:57 ` Peter Zijlstra
2016-01-06 20:21 ` Rob Landley
2016-01-06 18:57 ` Geert Uytterhoeven
2016-01-06 18:23 ` Rich Felker
2016-01-06 20:23 ` Michael S. Tsirkin
2016-01-06 23:53 ` Rich Felker
2016-01-07 13:37 ` Peter Zijlstra
2016-01-07 19:05 ` Rich Felker
2016-01-07 15:50 ` Michael S. Tsirkin
2016-01-07 17:48 ` Michael S. Tsirkin
2016-01-07 19:10 ` Rich Felker
2016-01-07 22:41 ` Michael S. Tsirkin
2016-01-08 4:25 ` Rich Felker
2016-01-08 7:23 ` Michael S. Tsirkin
2016-01-06 22:14 ` Michael S. Tsirkin
2015-12-31 19:09 ` [PATCH v2 32/32] virtio_ring: use virt_store_mb Michael S. Tsirkin
2016-01-01 17:23 ` Sergei Shtylyov
2016-01-03 9:01 ` Michael S. Tsirkin
2015-12-31 19:10 ` [PATCH v2 33/34] xenbus: use virt_xxx barriers Michael S. Tsirkin
2016-01-04 11:32 ` [Xen-devel] " David Vrabel
2016-01-04 12:03 ` Stefano Stabellini
2016-01-04 14:09 ` Peter Zijlstra
2015-12-31 19:10 ` [PATCH v2 34/34] xen/io: " Michael S. Tsirkin
2016-01-04 11:32 ` [Xen-devel] " David Vrabel
2016-01-04 12:05 ` Stefano Stabellini
2016-01-01 9:39 ` [PATCH v2 30/32] virtio_ring: update weak barriers to use __smp_xxx Michael S. Tsirkin
2016-01-01 10:21 ` Michael S. Tsirkin
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