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Subject[PATCH 28/31] arch, x86: Convert smp_mb__*
x86 is strongly ordered and all its atomic ops imply a full barrier.

Implement the two new primitives as the old ones were.

Signed-off-by: Peter Zijlstra <peterz@infradead.org>
---
arch/x86/include/asm/atomic.h | 7 +------
arch/x86/include/asm/barrier.h | 4 ++++
arch/x86/include/asm/bitops.h | 6 ++----
arch/x86/include/asm/sync_bitops.h | 2 +-
arch/x86/kernel/apic/hw_nmi.c | 2 +-
5 files changed, 9 insertions(+), 12 deletions(-)

--- a/arch/x86/include/asm/atomic.h
+++ b/arch/x86/include/asm/atomic.h
@@ -7,6 +7,7 @@
#include <asm/alternative.h>
#include <asm/cmpxchg.h>
#include <asm/rmwcc.h>
+#include <asm/barrier.h>

/*
* Atomic operations that C can't guarantee us. Useful for
@@ -256,12 +257,6 @@ static inline void atomic_or_long(unsign
: : "r" ((unsigned)(mask)), "m" (*(addr)) \
: "memory")

-/* Atomic operations are already serializing on x86 */
-#define smp_mb__before_atomic_dec() barrier()
-#define smp_mb__after_atomic_dec() barrier()
-#define smp_mb__before_atomic_inc() barrier()
-#define smp_mb__after_atomic_inc() barrier()
-
#ifdef CONFIG_X86_32
# include <asm/atomic64_32.h>
#else
--- a/arch/x86/include/asm/barrier.h
+++ b/arch/x86/include/asm/barrier.h
@@ -141,6 +141,10 @@ do { \

#endif

+/* Atomic operations are already serializing on x86 */
+#define smp_mb__before_atomic() barrier()
+#define smp_mb__after_atomic() barrier()
+
/*
* Stop RDTSC speculation. This is needed when you need to use RDTSC
* (or get_cycles or vread that possibly accesses the TSC) in a defined
--- a/arch/x86/include/asm/bitops.h
+++ b/arch/x86/include/asm/bitops.h
@@ -15,6 +15,7 @@
#include <linux/compiler.h>
#include <asm/alternative.h>
#include <asm/rmwcc.h>
+#include <asm/barrier.h>

#if BITS_PER_LONG == 32
# define _BITOPS_LONG_SHIFT 5
@@ -102,7 +103,7 @@ static inline void __set_bit(long nr, vo
*
* clear_bit() is atomic and may not be reordered. However, it does
* not contain a memory barrier, so if it is used for locking purposes,
- * you should call smp_mb__before_clear_bit() and/or smp_mb__after_clear_bit()
+ * you should call smp_mb__before_atomic() and/or smp_mb__after_atomic()
* in order to ensure changes are visible on other processors.
*/
static __always_inline void
@@ -156,9 +157,6 @@ static inline void __clear_bit_unlock(lo
__clear_bit(nr, addr);
}

-#define smp_mb__before_clear_bit() barrier()
-#define smp_mb__after_clear_bit() barrier()
-
/**
* __change_bit - Toggle a bit in memory
* @nr: the bit to change
--- a/arch/x86/include/asm/sync_bitops.h
+++ b/arch/x86/include/asm/sync_bitops.h
@@ -41,7 +41,7 @@ static inline void sync_set_bit(long nr,
*
* sync_clear_bit() is atomic and may not be reordered. However, it does
* not contain a memory barrier, so if it is used for locking purposes,
- * you should call smp_mb__before_clear_bit() and/or smp_mb__after_clear_bit()
+ * you should call smp_mb__before_atomic() and/or smp_mb__after_atomic()
* in order to ensure changes are visible on other processors.
*/
static inline void sync_clear_bit(long nr, volatile unsigned long *addr)
--- a/arch/x86/kernel/apic/hw_nmi.c
+++ b/arch/x86/kernel/apic/hw_nmi.c
@@ -57,7 +57,7 @@ void arch_trigger_all_cpu_backtrace(void
}

clear_bit(0, &backtrace_flag);
- smp_mb__after_clear_bit();
+ smp_mb__after_atomic();
}

static int __kprobes



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