* [PATCH] x86: Get rid of __HAVE_ARCH_CMPXCHG
@ 2014-07-11 9:51 Borislav Petkov
2014-07-11 10:19 ` Geert Uytterhoeven
0 siblings, 1 reply; 6+ messages in thread
From: Borislav Petkov @ 2014-07-11 9:51 UTC (permalink / raw)
To: Thomas Gleixner, Peter Zijlstra; +Cc: X86 ML, LKML
From: Borislav Petkov <bp@suse.de>
Both the 32-bit and 64-bit cmpxchg.h header define __HAVE_ARCH_CMPXCHG
and there's ifdeffery which checks it. But since both bitness define it,
we can just as well drop it and simpify a bit of code in doing that.
Signed-off-by: Borislav Petkov <bp@suse.de>
---
arch/x86/include/asm/cmpxchg.h | 2 --
arch/x86/include/asm/cmpxchg_32.h | 2 --
arch/x86/include/asm/cmpxchg_64.h | 2 --
arch/x86/include/asm/mc146818rtc.h | 2 +-
arch/x86/include/asm/mutex_32.h | 16 ++--------------
arch/x86/kernel/acpi/boot.c | 4 ----
kernel/locking/rtmutex.c | 2 +-
7 files changed, 4 insertions(+), 26 deletions(-)
diff --git a/arch/x86/include/asm/cmpxchg.h b/arch/x86/include/asm/cmpxchg.h
index d47786acb016..ad19841eddfe 100644
--- a/arch/x86/include/asm/cmpxchg.h
+++ b/arch/x86/include/asm/cmpxchg.h
@@ -143,7 +143,6 @@ extern void __add_wrong_size(void)
# include <asm/cmpxchg_64.h>
#endif
-#ifdef __HAVE_ARCH_CMPXCHG
#define cmpxchg(ptr, old, new) \
__cmpxchg(ptr, old, new, sizeof(*(ptr)))
@@ -152,7 +151,6 @@ extern void __add_wrong_size(void)
#define cmpxchg_local(ptr, old, new) \
__cmpxchg_local(ptr, old, new, sizeof(*(ptr)))
-#endif
/*
* xadd() adds "inc" to "*ptr" and atomically returns the previous
diff --git a/arch/x86/include/asm/cmpxchg_32.h b/arch/x86/include/asm/cmpxchg_32.h
index f8bf2eecab86..f7e142926481 100644
--- a/arch/x86/include/asm/cmpxchg_32.h
+++ b/arch/x86/include/asm/cmpxchg_32.h
@@ -34,8 +34,6 @@ static inline void set_64bit(volatile u64 *ptr, u64 value)
: "memory");
}
-#define __HAVE_ARCH_CMPXCHG 1
-
#ifdef CONFIG_X86_CMPXCHG64
#define cmpxchg64(ptr, o, n) \
((__typeof__(*(ptr)))__cmpxchg64((ptr), (unsigned long long)(o), \
diff --git a/arch/x86/include/asm/cmpxchg_64.h b/arch/x86/include/asm/cmpxchg_64.h
index 614be87f1a9b..1af94697aae5 100644
--- a/arch/x86/include/asm/cmpxchg_64.h
+++ b/arch/x86/include/asm/cmpxchg_64.h
@@ -6,8 +6,6 @@ static inline void set_64bit(volatile u64 *ptr, u64 val)
*ptr = val;
}
-#define __HAVE_ARCH_CMPXCHG 1
-
#define cmpxchg64(ptr, o, n) \
({ \
BUILD_BUG_ON(sizeof(*(ptr)) != 8); \
diff --git a/arch/x86/include/asm/mc146818rtc.h b/arch/x86/include/asm/mc146818rtc.h
index a55c7efcc4ed..0f555cc31984 100644
--- a/arch/x86/include/asm/mc146818rtc.h
+++ b/arch/x86/include/asm/mc146818rtc.h
@@ -13,7 +13,7 @@
#define RTC_ALWAYS_BCD 1 /* RTC operates in binary mode */
#endif
-#if defined(CONFIG_X86_32) && defined(__HAVE_ARCH_CMPXCHG)
+#if defined(CONFIG_X86_32)
/*
* This lock provides nmi access to the CMOS/RTC registers. It has some
* special properties. It is owned by a CPU and stores the index register
diff --git a/arch/x86/include/asm/mutex_32.h b/arch/x86/include/asm/mutex_32.h
index 0208c3c2cbc6..85e6cda45a02 100644
--- a/arch/x86/include/asm/mutex_32.h
+++ b/arch/x86/include/asm/mutex_32.h
@@ -100,23 +100,11 @@ do { \
static inline int __mutex_fastpath_trylock(atomic_t *count,
int (*fail_fn)(atomic_t *))
{
- /*
- * We have two variants here. The cmpxchg based one is the best one
- * because it never induce a false contention state. It is included
- * here because architectures using the inc/dec algorithms over the
- * xchg ones are much more likely to support cmpxchg natively.
- *
- * If not we fall back to the spinlock based variant - that is
- * just as efficient (and simpler) as a 'destructive' probing of
- * the mutex state would be.
- */
-#ifdef __HAVE_ARCH_CMPXCHG
+ /* cmpxchg because it never induces a false contention state. */
if (likely(atomic_cmpxchg(count, 1, 0) == 1))
return 1;
+
return 0;
-#else
- return fail_fn(count);
-#endif
}
#endif /* _ASM_X86_MUTEX_32_H */
diff --git a/arch/x86/kernel/acpi/boot.c b/arch/x86/kernel/acpi/boot.c
index 86281ffb96d6..a531f6564ed0 100644
--- a/arch/x86/kernel/acpi/boot.c
+++ b/arch/x86/kernel/acpi/boot.c
@@ -74,10 +74,6 @@ int acpi_fix_pin2_polarity __initdata;
static u64 acpi_lapic_addr __initdata = APIC_DEFAULT_PHYS_BASE;
#endif
-#ifndef __HAVE_ARCH_CMPXCHG
-#warning ACPI uses CMPXCHG, i486 and later hardware
-#endif
-
/* --------------------------------------------------------------------------
Boot-time Configuration
-------------------------------------------------------------------------- */
diff --git a/kernel/locking/rtmutex.c b/kernel/locking/rtmutex.c
index fc605941b9b8..28477b9ac6a9 100644
--- a/kernel/locking/rtmutex.c
+++ b/kernel/locking/rtmutex.c
@@ -73,7 +73,7 @@ static void fixup_rt_mutex_waiters(struct rt_mutex *lock)
* We can speed up the acquire/release, if the architecture
* supports cmpxchg and if there's no debugging state to be set up
*/
-#if defined(__HAVE_ARCH_CMPXCHG) && !defined(CONFIG_DEBUG_RT_MUTEXES)
+#ifndef CONFIG_DEBUG_RT_MUTEXES
# define rt_mutex_cmpxchg(l,c,n) (cmpxchg(&l->owner, c, n) == c)
static inline void mark_rt_mutex_waiters(struct rt_mutex *lock)
{
--
2.0.0
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH] x86: Get rid of __HAVE_ARCH_CMPXCHG
2014-07-11 9:51 [PATCH] x86: Get rid of __HAVE_ARCH_CMPXCHG Borislav Petkov
@ 2014-07-11 10:19 ` Geert Uytterhoeven
2014-07-11 10:28 ` Borislav Petkov
0 siblings, 1 reply; 6+ messages in thread
From: Geert Uytterhoeven @ 2014-07-11 10:19 UTC (permalink / raw)
To: Borislav Petkov; +Cc: Thomas Gleixner, Peter Zijlstra, X86 ML, LKML
On Fri, Jul 11, 2014 at 11:51 AM, Borislav Petkov <bp@alien8.de> wrote:
> From: Borislav Petkov <bp@suse.de>
>
> Both the 32-bit and 64-bit cmpxchg.h header define __HAVE_ARCH_CMPXCHG
> and there's ifdeffery which checks it. But since both bitness define it,
> we can just as well drop it and simpify a bit of code in doing that.
>
> Signed-off-by: Borislav Petkov <bp@suse.de>
> ---
> arch/x86/include/asm/cmpxchg.h | 2 --
> arch/x86/include/asm/cmpxchg_32.h | 2 --
> arch/x86/include/asm/cmpxchg_64.h | 2 --
> arch/x86/include/asm/mc146818rtc.h | 2 +-
> arch/x86/include/asm/mutex_32.h | 16 ++--------------
> arch/x86/kernel/acpi/boot.c | 4 ----
> kernel/locking/rtmutex.c | 2 +-
> 7 files changed, 4 insertions(+), 26 deletions(-)
> --- a/kernel/locking/rtmutex.c
> +++ b/kernel/locking/rtmutex.c
> @@ -73,7 +73,7 @@ static void fixup_rt_mutex_waiters(struct rt_mutex *lock)
> * We can speed up the acquire/release, if the architecture
> * supports cmpxchg and if there's no debugging state to be set up
> */
> -#if defined(__HAVE_ARCH_CMPXCHG) && !defined(CONFIG_DEBUG_RT_MUTEXES)
> +#ifndef CONFIG_DEBUG_RT_MUTEXES
> # define rt_mutex_cmpxchg(l,c,n) (cmpxchg(&l->owner, c, n) == c)
> static inline void mark_rt_mutex_waiters(struct rt_mutex *lock)
> {
What about non-x86? __HAVE_ARCH_CMPXCHG isn't always defined.
Gr{oetje,eeting}s,
Geert
--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org
In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
-- Linus Torvalds
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH] x86: Get rid of __HAVE_ARCH_CMPXCHG
2014-07-11 10:19 ` Geert Uytterhoeven
@ 2014-07-11 10:28 ` Borislav Petkov
2014-07-11 10:35 ` Geert Uytterhoeven
0 siblings, 1 reply; 6+ messages in thread
From: Borislav Petkov @ 2014-07-11 10:28 UTC (permalink / raw)
To: Geert Uytterhoeven; +Cc: Thomas Gleixner, Peter Zijlstra, X86 ML, LKML
On Fri, Jul 11, 2014 at 12:19:43PM +0200, Geert Uytterhoeven wrote:
> What about non-x86? __HAVE_ARCH_CMPXCHG isn't always defined.
Bah, this hunk was definitely not supposed to be there. Thanks for the
catch!
--
Regards/Gruss,
Boris.
Sent from a fat crate under my desk. Formatting is fine.
--
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH] x86: Get rid of __HAVE_ARCH_CMPXCHG
2014-07-11 10:28 ` Borislav Petkov
@ 2014-07-11 10:35 ` Geert Uytterhoeven
2014-07-11 10:43 ` Borislav Petkov
0 siblings, 1 reply; 6+ messages in thread
From: Geert Uytterhoeven @ 2014-07-11 10:35 UTC (permalink / raw)
To: Borislav Petkov; +Cc: Thomas Gleixner, Peter Zijlstra, X86 ML, LKML
On Fri, Jul 11, 2014 at 12:28 PM, Borislav Petkov <bp@alien8.de> wrote:
> On Fri, Jul 11, 2014 at 12:19:43PM +0200, Geert Uytterhoeven wrote:
>> What about non-x86? __HAVE_ARCH_CMPXCHG isn't always defined.
>
> Bah, this hunk was definitely not supposed to be there. Thanks for the
> catch!
IC.
In that case you also want to add a (new) "#define __HAVE_ARCH_CMPXCHG 1"
to one of the shared x86 header files, right?
Gr{oetje,eeting}s,
Geert
--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org
In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
-- Linus Torvalds
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH] x86: Get rid of __HAVE_ARCH_CMPXCHG
2014-07-11 10:35 ` Geert Uytterhoeven
@ 2014-07-11 10:43 ` Borislav Petkov
2014-07-12 0:30 ` [tip:x86/cleanups] x86: Simplify __HAVE_ARCH_CMPXCHG tests tip-bot for Borislav Petkov
0 siblings, 1 reply; 6+ messages in thread
From: Borislav Petkov @ 2014-07-11 10:43 UTC (permalink / raw)
To: Geert Uytterhoeven; +Cc: Thomas Gleixner, Peter Zijlstra, X86 ML, LKML
On Fri, Jul 11, 2014 at 12:35:43PM +0200, Geert Uytterhoeven wrote:
> In that case you also want to add a (new) "#define __HAVE_ARCH_CMPXCHG
> 1" to one of the shared x86 header files, right?
Yeah, I can't remove it after all. :-)
Diffstat is arch/x86/-only now, as it was supposed to be.
--
From: Borislav Petkov <bp@suse.de>
Subject: [PATCH] x86: Simplify __HAVE_ARCH_CMPXCHG tests
Both the 32-bit and 64-bit cmpxchg.h header define __HAVE_ARCH_CMPXCHG
and there's ifdeffery which checks it. But since both bitness define it,
we can just as well move it up to the main cmpxchg header and simpify a
bit of code in doing that.
Signed-off-by: Borislav Petkov <bp@suse.de>
---
arch/x86/include/asm/cmpxchg.h | 4 ++--
arch/x86/include/asm/cmpxchg_32.h | 2 --
arch/x86/include/asm/cmpxchg_64.h | 2 --
arch/x86/include/asm/mc146818rtc.h | 2 +-
arch/x86/include/asm/mutex_32.h | 16 ++--------------
arch/x86/kernel/acpi/boot.c | 4 ----
6 files changed, 5 insertions(+), 25 deletions(-)
diff --git a/arch/x86/include/asm/cmpxchg.h b/arch/x86/include/asm/cmpxchg.h
index d47786acb016..99c105d78b7e 100644
--- a/arch/x86/include/asm/cmpxchg.h
+++ b/arch/x86/include/asm/cmpxchg.h
@@ -4,6 +4,8 @@
#include <linux/compiler.h>
#include <asm/alternative.h> /* Provides LOCK_PREFIX */
+#define __HAVE_ARCH_CMPXCHG 1
+
/*
* Non-existant functions to indicate usage errors at link time
* (or compile-time if the compiler implements __compiletime_error().
@@ -143,7 +145,6 @@ extern void __add_wrong_size(void)
# include <asm/cmpxchg_64.h>
#endif
-#ifdef __HAVE_ARCH_CMPXCHG
#define cmpxchg(ptr, old, new) \
__cmpxchg(ptr, old, new, sizeof(*(ptr)))
@@ -152,7 +153,6 @@ extern void __add_wrong_size(void)
#define cmpxchg_local(ptr, old, new) \
__cmpxchg_local(ptr, old, new, sizeof(*(ptr)))
-#endif
/*
* xadd() adds "inc" to "*ptr" and atomically returns the previous
diff --git a/arch/x86/include/asm/cmpxchg_32.h b/arch/x86/include/asm/cmpxchg_32.h
index f8bf2eecab86..f7e142926481 100644
--- a/arch/x86/include/asm/cmpxchg_32.h
+++ b/arch/x86/include/asm/cmpxchg_32.h
@@ -34,8 +34,6 @@ static inline void set_64bit(volatile u64 *ptr, u64 value)
: "memory");
}
-#define __HAVE_ARCH_CMPXCHG 1
-
#ifdef CONFIG_X86_CMPXCHG64
#define cmpxchg64(ptr, o, n) \
((__typeof__(*(ptr)))__cmpxchg64((ptr), (unsigned long long)(o), \
diff --git a/arch/x86/include/asm/cmpxchg_64.h b/arch/x86/include/asm/cmpxchg_64.h
index 614be87f1a9b..1af94697aae5 100644
--- a/arch/x86/include/asm/cmpxchg_64.h
+++ b/arch/x86/include/asm/cmpxchg_64.h
@@ -6,8 +6,6 @@ static inline void set_64bit(volatile u64 *ptr, u64 val)
*ptr = val;
}
-#define __HAVE_ARCH_CMPXCHG 1
-
#define cmpxchg64(ptr, o, n) \
({ \
BUILD_BUG_ON(sizeof(*(ptr)) != 8); \
diff --git a/arch/x86/include/asm/mc146818rtc.h b/arch/x86/include/asm/mc146818rtc.h
index a55c7efcc4ed..0f555cc31984 100644
--- a/arch/x86/include/asm/mc146818rtc.h
+++ b/arch/x86/include/asm/mc146818rtc.h
@@ -13,7 +13,7 @@
#define RTC_ALWAYS_BCD 1 /* RTC operates in binary mode */
#endif
-#if defined(CONFIG_X86_32) && defined(__HAVE_ARCH_CMPXCHG)
+#if defined(CONFIG_X86_32)
/*
* This lock provides nmi access to the CMOS/RTC registers. It has some
* special properties. It is owned by a CPU and stores the index register
diff --git a/arch/x86/include/asm/mutex_32.h b/arch/x86/include/asm/mutex_32.h
index 0208c3c2cbc6..85e6cda45a02 100644
--- a/arch/x86/include/asm/mutex_32.h
+++ b/arch/x86/include/asm/mutex_32.h
@@ -100,23 +100,11 @@ do { \
static inline int __mutex_fastpath_trylock(atomic_t *count,
int (*fail_fn)(atomic_t *))
{
- /*
- * We have two variants here. The cmpxchg based one is the best one
- * because it never induce a false contention state. It is included
- * here because architectures using the inc/dec algorithms over the
- * xchg ones are much more likely to support cmpxchg natively.
- *
- * If not we fall back to the spinlock based variant - that is
- * just as efficient (and simpler) as a 'destructive' probing of
- * the mutex state would be.
- */
-#ifdef __HAVE_ARCH_CMPXCHG
+ /* cmpxchg because it never induces a false contention state. */
if (likely(atomic_cmpxchg(count, 1, 0) == 1))
return 1;
+
return 0;
-#else
- return fail_fn(count);
-#endif
}
#endif /* _ASM_X86_MUTEX_32_H */
diff --git a/arch/x86/kernel/acpi/boot.c b/arch/x86/kernel/acpi/boot.c
index 86281ffb96d6..a531f6564ed0 100644
--- a/arch/x86/kernel/acpi/boot.c
+++ b/arch/x86/kernel/acpi/boot.c
@@ -74,10 +74,6 @@ int acpi_fix_pin2_polarity __initdata;
static u64 acpi_lapic_addr __initdata = APIC_DEFAULT_PHYS_BASE;
#endif
-#ifndef __HAVE_ARCH_CMPXCHG
-#warning ACPI uses CMPXCHG, i486 and later hardware
-#endif
-
/* --------------------------------------------------------------------------
Boot-time Configuration
-------------------------------------------------------------------------- */
--
2.0.0
--
Regards/Gruss,
Boris.
Sent from a fat crate under my desk. Formatting is fine.
--
^ permalink raw reply [flat|nested] 6+ messages in thread
* [tip:x86/cleanups] x86: Simplify __HAVE_ARCH_CMPXCHG tests
2014-07-11 10:43 ` Borislav Petkov
@ 2014-07-12 0:30 ` tip-bot for Borislav Petkov
0 siblings, 0 replies; 6+ messages in thread
From: tip-bot for Borislav Petkov @ 2014-07-12 0:30 UTC (permalink / raw)
To: linux-tip-commits; +Cc: linux-kernel, hpa, mingo, tglx, hpa, bp
Commit-ID: b08ee5f7e4135d64b8edd769367f8964a725122e
Gitweb: http://git.kernel.org/tip/b08ee5f7e4135d64b8edd769367f8964a725122e
Author: Borislav Petkov <bp@suse.de>
AuthorDate: Fri, 11 Jul 2014 12:43:38 +0200
Committer: H. Peter Anvin <hpa@linux.intel.com>
CommitDate: Fri, 11 Jul 2014 17:28:51 -0700
x86: Simplify __HAVE_ARCH_CMPXCHG tests
Both the 32-bit and 64-bit cmpxchg.h header define __HAVE_ARCH_CMPXCHG
and there's ifdeffery which checks it. But since both bitness define it,
we can just as well move it up to the main cmpxchg header and simpify a
bit of code in doing that.
Signed-off-by: Borislav Petkov <bp@suse.de>
Link: http://lkml.kernel.org/r/20140711104338.GB17083@pd.tnic
Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>
---
arch/x86/include/asm/cmpxchg.h | 4 ++--
arch/x86/include/asm/cmpxchg_32.h | 2 --
arch/x86/include/asm/cmpxchg_64.h | 2 --
arch/x86/include/asm/mc146818rtc.h | 2 +-
arch/x86/include/asm/mutex_32.h | 16 ++--------------
arch/x86/kernel/acpi/boot.c | 4 ----
6 files changed, 5 insertions(+), 25 deletions(-)
diff --git a/arch/x86/include/asm/cmpxchg.h b/arch/x86/include/asm/cmpxchg.h
index d47786a..99c105d7 100644
--- a/arch/x86/include/asm/cmpxchg.h
+++ b/arch/x86/include/asm/cmpxchg.h
@@ -4,6 +4,8 @@
#include <linux/compiler.h>
#include <asm/alternative.h> /* Provides LOCK_PREFIX */
+#define __HAVE_ARCH_CMPXCHG 1
+
/*
* Non-existant functions to indicate usage errors at link time
* (or compile-time if the compiler implements __compiletime_error().
@@ -143,7 +145,6 @@ extern void __add_wrong_size(void)
# include <asm/cmpxchg_64.h>
#endif
-#ifdef __HAVE_ARCH_CMPXCHG
#define cmpxchg(ptr, old, new) \
__cmpxchg(ptr, old, new, sizeof(*(ptr)))
@@ -152,7 +153,6 @@ extern void __add_wrong_size(void)
#define cmpxchg_local(ptr, old, new) \
__cmpxchg_local(ptr, old, new, sizeof(*(ptr)))
-#endif
/*
* xadd() adds "inc" to "*ptr" and atomically returns the previous
diff --git a/arch/x86/include/asm/cmpxchg_32.h b/arch/x86/include/asm/cmpxchg_32.h
index f8bf2ee..f7e1429 100644
--- a/arch/x86/include/asm/cmpxchg_32.h
+++ b/arch/x86/include/asm/cmpxchg_32.h
@@ -34,8 +34,6 @@ static inline void set_64bit(volatile u64 *ptr, u64 value)
: "memory");
}
-#define __HAVE_ARCH_CMPXCHG 1
-
#ifdef CONFIG_X86_CMPXCHG64
#define cmpxchg64(ptr, o, n) \
((__typeof__(*(ptr)))__cmpxchg64((ptr), (unsigned long long)(o), \
diff --git a/arch/x86/include/asm/cmpxchg_64.h b/arch/x86/include/asm/cmpxchg_64.h
index 614be87..1af9469 100644
--- a/arch/x86/include/asm/cmpxchg_64.h
+++ b/arch/x86/include/asm/cmpxchg_64.h
@@ -6,8 +6,6 @@ static inline void set_64bit(volatile u64 *ptr, u64 val)
*ptr = val;
}
-#define __HAVE_ARCH_CMPXCHG 1
-
#define cmpxchg64(ptr, o, n) \
({ \
BUILD_BUG_ON(sizeof(*(ptr)) != 8); \
diff --git a/arch/x86/include/asm/mc146818rtc.h b/arch/x86/include/asm/mc146818rtc.h
index a55c7ef..0f555cc 100644
--- a/arch/x86/include/asm/mc146818rtc.h
+++ b/arch/x86/include/asm/mc146818rtc.h
@@ -13,7 +13,7 @@
#define RTC_ALWAYS_BCD 1 /* RTC operates in binary mode */
#endif
-#if defined(CONFIG_X86_32) && defined(__HAVE_ARCH_CMPXCHG)
+#if defined(CONFIG_X86_32)
/*
* This lock provides nmi access to the CMOS/RTC registers. It has some
* special properties. It is owned by a CPU and stores the index register
diff --git a/arch/x86/include/asm/mutex_32.h b/arch/x86/include/asm/mutex_32.h
index 0208c3c..85e6cda 100644
--- a/arch/x86/include/asm/mutex_32.h
+++ b/arch/x86/include/asm/mutex_32.h
@@ -100,23 +100,11 @@ do { \
static inline int __mutex_fastpath_trylock(atomic_t *count,
int (*fail_fn)(atomic_t *))
{
- /*
- * We have two variants here. The cmpxchg based one is the best one
- * because it never induce a false contention state. It is included
- * here because architectures using the inc/dec algorithms over the
- * xchg ones are much more likely to support cmpxchg natively.
- *
- * If not we fall back to the spinlock based variant - that is
- * just as efficient (and simpler) as a 'destructive' probing of
- * the mutex state would be.
- */
-#ifdef __HAVE_ARCH_CMPXCHG
+ /* cmpxchg because it never induces a false contention state. */
if (likely(atomic_cmpxchg(count, 1, 0) == 1))
return 1;
+
return 0;
-#else
- return fail_fn(count);
-#endif
}
#endif /* _ASM_X86_MUTEX_32_H */
diff --git a/arch/x86/kernel/acpi/boot.c b/arch/x86/kernel/acpi/boot.c
index 86281ff..a531f65 100644
--- a/arch/x86/kernel/acpi/boot.c
+++ b/arch/x86/kernel/acpi/boot.c
@@ -74,10 +74,6 @@ int acpi_fix_pin2_polarity __initdata;
static u64 acpi_lapic_addr __initdata = APIC_DEFAULT_PHYS_BASE;
#endif
-#ifndef __HAVE_ARCH_CMPXCHG
-#warning ACPI uses CMPXCHG, i486 and later hardware
-#endif
-
/* --------------------------------------------------------------------------
Boot-time Configuration
-------------------------------------------------------------------------- */
^ permalink raw reply [flat|nested] 6+ messages in thread
end of thread, other threads:[~2014-07-12 0:30 UTC | newest]
Thread overview: 6+ messages (download: mbox.gz / follow: Atom feed)
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2014-07-11 9:51 [PATCH] x86: Get rid of __HAVE_ARCH_CMPXCHG Borislav Petkov
2014-07-11 10:19 ` Geert Uytterhoeven
2014-07-11 10:28 ` Borislav Petkov
2014-07-11 10:35 ` Geert Uytterhoeven
2014-07-11 10:43 ` Borislav Petkov
2014-07-12 0:30 ` [tip:x86/cleanups] x86: Simplify __HAVE_ARCH_CMPXCHG tests tip-bot for Borislav Petkov
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