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| Started by | Boqun Feng <boqun.feng@gmail.com> |
|---|---|
| First post | 2015-08-28 04:50 +0200 |
| Last post | 2015-08-28 14:00 +0200 |
| Articles | 3 — 2 participants |
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[RFC 2/5] atomics: introduce arch_atomic_op_{acquire,release,fence} helpers Boqun Feng <boqun.feng@gmail.com> - 2015-08-28 04:50 +0200
Re: [RFC 2/5] atomics: introduce arch_atomic_op_{acquire,release,fence} helpers Peter Zijlstra <peterz@infradead.org> - 2015-08-28 13:40 +0200
Re: [RFC 2/5] atomics: introduce arch_atomic_op_{acquire,release,fence} helpers Boqun Feng <boqun.feng@gmail.com> - 2015-08-28 14:00 +0200
| From | Boqun Feng <boqun.feng@gmail.com> |
|---|---|
| Date | 2015-08-28 04:50 +0200 |
| Subject | [RFC 2/5] atomics: introduce arch_atomic_op_{acquire,release,fence} helpers |
| Message-ID | <q2hTP-6SU-1@gated-at.bofh.it> |
Some architectures may have their special barriers for acquire, release
and fence semantics, general memory barriers(smp_mb__*_atomic()) in
__atomic_op_*() may be too strong, so arch_atomic_op_*() helpers are
introduced for architectures to provide their own version helpers to
build different variants based on _relaxed variants.
Signed-off-by: Boqun Feng <boqun.feng@gmail.com>
---
include/linux/atomic.h | 16 ++++++++++++++++
1 file changed, 16 insertions(+)
diff --git a/include/linux/atomic.h b/include/linux/atomic.h
index 00a5763..622255b 100644
--- a/include/linux/atomic.h
+++ b/include/linux/atomic.h
@@ -34,20 +34,33 @@
* The idea here is to build acquire/release variants by adding explicit
* barriers on top of the relaxed variant. In the case where the relaxed
* variant is already fully ordered, no additional barriers are needed.
+ *
+ * Besides, if an arch has a special barrier for acquire/release, it could
+ * implement its own arch_atomic_op_* and use the same framework for building
+ * variants
*/
+#ifndef arch_atomic_op_acquire
#define __atomic_op_acquire(op, args...) \
({ \
typeof(op##_relaxed(args)) __ret = op##_relaxed(args); \
smp_mb__after_atomic(); \
__ret; \
})
+#else
+#define __atomic_op_acquire arch_atomic_op_acquire
+#endif
+#ifndef arch_atomic_op_release
#define __atomic_op_release(op, args...) \
({ \
smp_mb__before_atomic(); \
op##_relaxed(args); \
})
+#else
+#define __atomic_op_release arch_atomic_op_release
+#endif
+#ifndef arch_atomic_op_fence
#define __atomic_op_fence(op, args...) \
({ \
typeof(op##_relaxed(args)) __ret; \
@@ -56,6 +69,9 @@
smp_mb__after_atomic(); \
__ret; \
})
+#else
+#define __atomic_op_fence arch_atomic_op_fence
+#endif
/* atomic_add_return_relaxed */
#ifndef atomic_add_return_relaxed
--
2.5.0
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| From | Peter Zijlstra <peterz@infradead.org> |
|---|---|
| Date | 2015-08-28 13:40 +0200 |
| Subject | Re: [RFC 2/5] atomics: introduce arch_atomic_op_{acquire,release,fence} helpers |
| Message-ID | <q2qaJ-20a-9@gated-at.bofh.it> |
| In reply to | #1215065 |
On Fri, Aug 28, 2015 at 10:48:16AM +0800, Boqun Feng wrote:
> Some architectures may have their special barriers for acquire, release
> and fence semantics, general memory barriers(smp_mb__*_atomic()) in
> __atomic_op_*() may be too strong, so arch_atomic_op_*() helpers are
> introduced for architectures to provide their own version helpers to
> build different variants based on _relaxed variants.
>
> Signed-off-by: Boqun Feng <boqun.feng@gmail.com>
> ---
> include/linux/atomic.h | 16 ++++++++++++++++
> 1 file changed, 16 insertions(+)
>
> diff --git a/include/linux/atomic.h b/include/linux/atomic.h
> index 00a5763..622255b 100644
> --- a/include/linux/atomic.h
> +++ b/include/linux/atomic.h
> @@ -34,20 +34,33 @@
> * The idea here is to build acquire/release variants by adding explicit
> * barriers on top of the relaxed variant. In the case where the relaxed
> * variant is already fully ordered, no additional barriers are needed.
> + *
> + * Besides, if an arch has a special barrier for acquire/release, it could
> + * implement its own arch_atomic_op_* and use the same framework for building
> + * variants
> */
> +#ifndef arch_atomic_op_acquire
> #define __atomic_op_acquire(op, args...) \
> ({ \
> typeof(op##_relaxed(args)) __ret = op##_relaxed(args); \
> smp_mb__after_atomic(); \
> __ret; \
> })
> +#else
> +#define __atomic_op_acquire arch_atomic_op_acquire
> +#endif
Not really a fan of this, its not consistent with the existing #ifndef
guard style.
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| From | Boqun Feng <boqun.feng@gmail.com> |
|---|---|
| Date | 2015-08-28 14:00 +0200 |
| Subject | Re: [RFC 2/5] atomics: introduce arch_atomic_op_{acquire,release,fence} helpers |
| Message-ID | <q2qu6-2n5-9@gated-at.bofh.it> |
| In reply to | #1215293 |
[Multipart message — attachments visible in raw view] — view raw
Hi Peter,
On Fri, Aug 28, 2015 at 01:36:14PM +0200, Peter Zijlstra wrote:
> On Fri, Aug 28, 2015 at 10:48:16AM +0800, Boqun Feng wrote:
> > Some architectures may have their special barriers for acquire, release
> > and fence semantics, general memory barriers(smp_mb__*_atomic()) in
> > __atomic_op_*() may be too strong, so arch_atomic_op_*() helpers are
> > introduced for architectures to provide their own version helpers to
> > build different variants based on _relaxed variants.
> >
> > Signed-off-by: Boqun Feng <boqun.feng@gmail.com>
> > ---
> > include/linux/atomic.h | 16 ++++++++++++++++
> > 1 file changed, 16 insertions(+)
> >
> > diff --git a/include/linux/atomic.h b/include/linux/atomic.h
> > index 00a5763..622255b 100644
> > --- a/include/linux/atomic.h
> > +++ b/include/linux/atomic.h
> > @@ -34,20 +34,33 @@
> > * The idea here is to build acquire/release variants by adding explicit
> > * barriers on top of the relaxed variant. In the case where the relaxed
> > * variant is already fully ordered, no additional barriers are needed.
> > + *
> > + * Besides, if an arch has a special barrier for acquire/release, it could
> > + * implement its own arch_atomic_op_* and use the same framework for building
> > + * variants
> > */
> > +#ifndef arch_atomic_op_acquire
> > #define __atomic_op_acquire(op, args...) \
> > ({ \
> > typeof(op##_relaxed(args)) __ret = op##_relaxed(args); \
> > smp_mb__after_atomic(); \
> > __ret; \
> > })
> > +#else
> > +#define __atomic_op_acquire arch_atomic_op_acquire
> > +#endif
>
> Not really a fan of this, its not consistent with the existing #ifndef
> guard style.
You suggestion is that I should:
#ifndef __atomic_op_acquire
#define __atomic_op_acquire(op, args...)
({
...
})
#endif
... and define powerpc specific __atomic_op_acquire in asm/atomic.h?
Regards,
Boqun
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