From: Boqun Feng <boqun.feng@gmail.com>
To: "Michael S. Tsirkin" <mst@redhat.com>
Cc: linux-kernel@vger.kernel.org,
Peter Zijlstra <peterz@infradead.org>,
Arnd Bergmann <arnd@arndb.de>,
linux-arch@vger.kernel.org,
Andrew Cooper <andrew.cooper3@citrix.com>,
virtualization@lists.linux-foundation.org,
Stefano Stabellini <stefano.stabellini@eu.citrix.com>,
Thomas Gleixner <tglx@linutronix.de>, Ingo Molnar <mingo@elte.hu>,
"H. Peter Anvin" <hpa@zytor.com>,
David Miller <davem@davemloft.net>,
linux-ia64@vger.kernel.org, linuxppc-dev@lists.ozlabs.org,
linux-s390@vger.kernel.org, sparclinux@vger.kernel.org,
linux-arm-kernel@lists.infradead.org,
linux-metag@vger.kernel.org, linux-mips@linux-mips.org,
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Benjamin Herrenschmidt <benh@kernel.crashing.org>,
Paul Mackerras <paulus@samba.org>,
Michael Ellerman <mpe@ellerman.id.au>,
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: Tue, 5 Jan 2016 09:36:55 +0800 [thread overview]
Message-ID: <20160105013648.GA1256@fixme-laptop.cn.ibm.com> (raw)
In-Reply-To: <1451572003-2440-16-git-send-email-mst@redhat.com>
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 <mst@redhat.com>
> Acked-by: Arnd Bergmann <arnd@arndb.de>
> ---
> 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 majordomo@vger.kernel.org
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> Please read the FAQ at http://www.tux.org/lkml/
next prev parent reply other threads:[~2016-01-05 1:37 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 [this message]
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
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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