[v4,1/1] eal: add 128-bit compare exchange (x86-64 only)
diff mbox series

Message ID 20190403173438.23691-2-gage.eads@intel.com
State Superseded, archived
Delegated to: Thomas Monjalon
Headers show
Series
  • Add 128-bit compare and set
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ci/checkpatch success coding style OK
ci/Intel-compilation success Compilation OK
ci/mellanox-Performance-Testing success Performance Testing PASS
ci/intel-Performance-Testing success Performance Testing PASS

Commit Message

Eads, Gage April 3, 2019, 5:34 p.m. UTC
This operation can be used for non-blocking algorithms, such as a
non-blocking stack or ring.

Signed-off-by: Gage Eads <gage.eads@intel.com>
Reviewed-by: Honnappa Nagarahalli <honnappa.nagarahalli@arm.com>
---
 .../common/include/arch/x86/rte_atomic_64.h        | 81 ++++++++++++++++++++++
 1 file changed, 81 insertions(+)

Comments

Thomas Monjalon April 3, 2019, 7:04 p.m. UTC | #1
03/04/2019 19:34, Gage Eads:
> This operation can be used for non-blocking algorithms, such as a
> non-blocking stack or ring.
> 
> Signed-off-by: Gage Eads <gage.eads@intel.com>
> Reviewed-by: Honnappa Nagarahalli <honnappa.nagarahalli@arm.com>
> ---
> --- a/lib/librte_eal/common/include/arch/x86/rte_atomic_64.h
> +++ b/lib/librte_eal/common/include/arch/x86/rte_atomic_64.h
> +/**
> + * An atomic compare and set function used by the mutex functions.
> + * (Atomically) Equivalent to:
> + *   if (*dst == *exp)
> + *     *dst = *src
> + *   else
> + *     *exp = *dst
> + *
> + * @note The success and failure arguments must be one of the __ATOMIC_* values
> + * defined in the C++11 standard. For details on their behavior, refer to the
> + * standard.
> + *
> + * @param dst
> + *   The destination into which the value will be written.
> + * @param exp
> + *   Pointer to the expected value. If the operation fails, this memory is
> + *   updated with the actual value.
> + * @param src
> + *   Pointer to the new value.
> + * @param weak
> + *   A value of true allows the comparison to spuriously fail and allows the
> + *   'exp' update to occur non-atomically (i.e. a torn read may occur).
> + *   Implementations may ignore this argument and only implement the strong
> + *   variant.
> + * @param success
> + *   If successful, the operation's memory behavior conforms to this (or a
> + *   stronger) model.
> + * @param failure
> + *   If unsuccessful, the operation's memory behavior conforms to this (or a
> + *   stronger) model. This argument cannot be __ATOMIC_RELEASE,
> + *   __ATOMIC_ACQ_REL, or a stronger model than success.
> + * @return
> + *   Non-zero on success; 0 on failure.
> + */
> +static inline int __rte_experimental
> +rte_atomic128_cmp_exchange(rte_int128_t *dst,
> +			   rte_int128_t *exp,
> +			   const rte_int128_t *src,
> +			   unsigned int weak,
> +			   int success,
> +			   int failure)

I was thinking about keeping the doxygen in the generic file.
Is it possible?
Eads, Gage April 3, 2019, 7:21 p.m. UTC | #2
> 03/04/2019 19:34, Gage Eads:
> > This operation can be used for non-blocking algorithms, such as a
> > non-blocking stack or ring.
> >
> > Signed-off-by: Gage Eads <gage.eads@intel.com>
> > Reviewed-by: Honnappa Nagarahalli <honnappa.nagarahalli@arm.com>
> > ---
> > --- a/lib/librte_eal/common/include/arch/x86/rte_atomic_64.h
> > +++ b/lib/librte_eal/common/include/arch/x86/rte_atomic_64.h
> > +/**
> > + * An atomic compare and set function used by the mutex functions.
> > + * (Atomically) Equivalent to:
> > + *   if (*dst == *exp)
> > + *     *dst = *src
> > + *   else
> > + *     *exp = *dst
> > + *
> > + * @note The success and failure arguments must be one of the
> > +__ATOMIC_* values
> > + * defined in the C++11 standard. For details on their behavior,
> > +refer to the
> > + * standard.
> > + *
> > + * @param dst
> > + *   The destination into which the value will be written.
> > + * @param exp
> > + *   Pointer to the expected value. If the operation fails, this memory is
> > + *   updated with the actual value.
> > + * @param src
> > + *   Pointer to the new value.
> > + * @param weak
> > + *   A value of true allows the comparison to spuriously fail and allows the
> > + *   'exp' update to occur non-atomically (i.e. a torn read may occur).
> > + *   Implementations may ignore this argument and only implement the
> strong
> > + *   variant.
> > + * @param success
> > + *   If successful, the operation's memory behavior conforms to this (or a
> > + *   stronger) model.
> > + * @param failure
> > + *   If unsuccessful, the operation's memory behavior conforms to this (or
> a
> > + *   stronger) model. This argument cannot be __ATOMIC_RELEASE,
> > + *   __ATOMIC_ACQ_REL, or a stronger model than success.
> > + * @return
> > + *   Non-zero on success; 0 on failure.
> > + */
> > +static inline int __rte_experimental
> > +rte_atomic128_cmp_exchange(rte_int128_t *dst,
> > +			   rte_int128_t *exp,
> > +			   const rte_int128_t *src,
> > +			   unsigned int weak,
> > +			   int success,
> > +			   int failure)
> 
> I was thinking about keeping the doxygen in the generic file.
> Is it possible?
> 

We'd need to include the definition of rte_int128_t, so we'd also need either an ifdef on RTE_ARCH_64 or RTE_ARCH_X86_64 to protect 32-bit builds. That macro would prevent doxygen from parsing that section, unless we add a workaround like, for example:

#if defined(RTE_ARCH_64) || defined(__DOXYGEN__)

So the patch would look like the v3, with the declaration in generic/rte_atomic.h, but with that preprocessor change. If we change RTE_ARCH_X86_64 to RTE_ARCH_64, I'd add a note clarifying that it's only implemented for x86-64. What do you think?
Thomas Monjalon April 3, 2019, 7:27 p.m. UTC | #3
03/04/2019 21:21, Eads, Gage:
> > 03/04/2019 19:34, Gage Eads:
> > > This operation can be used for non-blocking algorithms, such as a
> > > non-blocking stack or ring.
> > >
> > > Signed-off-by: Gage Eads <gage.eads@intel.com>
> > > Reviewed-by: Honnappa Nagarahalli <honnappa.nagarahalli@arm.com>
> > > ---
> > > --- a/lib/librte_eal/common/include/arch/x86/rte_atomic_64.h
> > > +++ b/lib/librte_eal/common/include/arch/x86/rte_atomic_64.h
> > > +/**
> > > + * An atomic compare and set function used by the mutex functions.
> > > + * (Atomically) Equivalent to:
> > > + *   if (*dst == *exp)
> > > + *     *dst = *src
> > > + *   else
> > > + *     *exp = *dst
> > > + *
> > > + * @note The success and failure arguments must be one of the
> > > +__ATOMIC_* values
> > > + * defined in the C++11 standard. For details on their behavior,
> > > +refer to the
> > > + * standard.
> > > + *
> > > + * @param dst
> > > + *   The destination into which the value will be written.
> > > + * @param exp
> > > + *   Pointer to the expected value. If the operation fails, this memory is
> > > + *   updated with the actual value.
> > > + * @param src
> > > + *   Pointer to the new value.
> > > + * @param weak
> > > + *   A value of true allows the comparison to spuriously fail and allows the
> > > + *   'exp' update to occur non-atomically (i.e. a torn read may occur).
> > > + *   Implementations may ignore this argument and only implement the
> > strong
> > > + *   variant.
> > > + * @param success
> > > + *   If successful, the operation's memory behavior conforms to this (or a
> > > + *   stronger) model.
> > > + * @param failure
> > > + *   If unsuccessful, the operation's memory behavior conforms to this (or
> > a
> > > + *   stronger) model. This argument cannot be __ATOMIC_RELEASE,
> > > + *   __ATOMIC_ACQ_REL, or a stronger model than success.
> > > + * @return
> > > + *   Non-zero on success; 0 on failure.
> > > + */
> > > +static inline int __rte_experimental
> > > +rte_atomic128_cmp_exchange(rte_int128_t *dst,
> > > +			   rte_int128_t *exp,
> > > +			   const rte_int128_t *src,
> > > +			   unsigned int weak,
> > > +			   int success,
> > > +			   int failure)
> > 
> > I was thinking about keeping the doxygen in the generic file.
> > Is it possible?
> > 
> 
> We'd need to include the definition of rte_int128_t, so we'd also need either an ifdef on RTE_ARCH_64 or RTE_ARCH_X86_64 to protect 32-bit builds. That macro would prevent doxygen from parsing that section, unless we add a workaround like, for example:
> 
> #if defined(RTE_ARCH_64) || defined(__DOXYGEN__)
> 
> So the patch would look like the v3, with the declaration in generic/rte_atomic.h, but with that preprocessor change. If we change RTE_ARCH_X86_64 to RTE_ARCH_64, I'd add a note clarifying that it's only implemented for x86-64. What do you think?

I would like to see the doc in the generic file
and the implementation in the x86 file.

I tried forward declaration of the typedef:
	struct rte_int128;
	typedef struct rte_int128 rte_int128_t;
I don't why it does not work.
So I'm trying to protect the declaration with
	#ifdef __DOXYGEN__

Patch
diff mbox series

diff --git a/lib/librte_eal/common/include/arch/x86/rte_atomic_64.h b/lib/librte_eal/common/include/arch/x86/rte_atomic_64.h
index fd2ec9c53..49bce32c7 100644
--- a/lib/librte_eal/common/include/arch/x86/rte_atomic_64.h
+++ b/lib/librte_eal/common/include/arch/x86/rte_atomic_64.h
@@ -34,6 +34,7 @@ 
 /*
  * Inspired from FreeBSD src/sys/amd64/include/atomic.h
  * Copyright (c) 1998 Doug Rabson
+ * Copyright (c) 2019 Intel Corporation
  * All rights reserved.
  */
 
@@ -46,6 +47,7 @@ 
 
 #include <stdint.h>
 #include <rte_common.h>
+#include <rte_compat.h>
 #include <rte_atomic.h>
 
 /*------------------------- 64 bit atomic operations -------------------------*/
@@ -208,4 +210,83 @@  static inline void rte_atomic64_clear(rte_atomic64_t *v)
 }
 #endif
 
+/*------------------------ 128 bit atomic operations -------------------------*/
+
+/**
+ * 128-bit integer structure.
+ */
+RTE_STD_C11
+typedef struct {
+	RTE_STD_C11
+	union {
+		uint64_t val[2];
+		__int128 int128;
+	};
+} __rte_aligned(16) rte_int128_t;
+
+/**
+ * An atomic compare and set function used by the mutex functions.
+ * (Atomically) Equivalent to:
+ *   if (*dst == *exp)
+ *     *dst = *src
+ *   else
+ *     *exp = *dst
+ *
+ * @note The success and failure arguments must be one of the __ATOMIC_* values
+ * defined in the C++11 standard. For details on their behavior, refer to the
+ * standard.
+ *
+ * @param dst
+ *   The destination into which the value will be written.
+ * @param exp
+ *   Pointer to the expected value. If the operation fails, this memory is
+ *   updated with the actual value.
+ * @param src
+ *   Pointer to the new value.
+ * @param weak
+ *   A value of true allows the comparison to spuriously fail and allows the
+ *   'exp' update to occur non-atomically (i.e. a torn read may occur).
+ *   Implementations may ignore this argument and only implement the strong
+ *   variant.
+ * @param success
+ *   If successful, the operation's memory behavior conforms to this (or a
+ *   stronger) model.
+ * @param failure
+ *   If unsuccessful, the operation's memory behavior conforms to this (or a
+ *   stronger) model. This argument cannot be __ATOMIC_RELEASE,
+ *   __ATOMIC_ACQ_REL, or a stronger model than success.
+ * @return
+ *   Non-zero on success; 0 on failure.
+ */
+static inline int __rte_experimental
+rte_atomic128_cmp_exchange(rte_int128_t *dst,
+			   rte_int128_t *exp,
+			   const rte_int128_t *src,
+			   unsigned int weak,
+			   int success,
+			   int failure)
+{
+	RTE_SET_USED(weak);
+	RTE_SET_USED(success);
+	RTE_SET_USED(failure);
+	uint8_t res;
+
+	asm volatile (
+		      MPLOCKED
+		      "cmpxchg16b %[dst];"
+		      " sete %[res]"
+		      : [dst] "=m" (dst->val[0]),
+			"=a" (exp->val[0]),
+			"=d" (exp->val[1]),
+			[res] "=r" (res)
+		      : "b" (src->val[0]),
+			"c" (src->val[1]),
+			"a" (exp->val[0]),
+			"d" (exp->val[1]),
+			"m" (dst->val[0])
+		      : "memory");
+
+	return res;
+}
+
 #endif /* _RTE_ATOMIC_X86_64_H_ */