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8a44971841
This patch is meant to cleanup the handling of read_barrier_depends and
smp_read_barrier_depends. In multiple spots in the kernel headers
read_barrier_depends is defined as "do {} while (0)", however we then go
into the SMP vs non-SMP sections and have the SMP version reference
read_barrier_depends, and the non-SMP define it as yet another empty
do/while.
With this commit I went through and cleaned out the duplicate definitions
and reduced the number of definitions down to 2 per header. In addition I
moved the 50 line comments for the macro from the x86 and mips headers that
defined it as an empty do/while to those that were actually defining the
macro, alpha and blackfin.
Signed-off-by: Alexander Duyck <alexander.h.duyck@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
70 lines
1.8 KiB
C
70 lines
1.8 KiB
C
#ifndef _ASM_UM_BARRIER_H_
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#define _ASM_UM_BARRIER_H_
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#include <asm/asm.h>
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#include <asm/segment.h>
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#include <asm/cpufeature.h>
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#include <asm/cmpxchg.h>
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#include <asm/nops.h>
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#include <linux/kernel.h>
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#include <linux/irqflags.h>
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/*
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* Force strict CPU ordering.
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* And yes, this is required on UP too when we're talking
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* to devices.
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*/
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#ifdef CONFIG_X86_32
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#define mb() alternative("lock; addl $0,0(%%esp)", "mfence", X86_FEATURE_XMM2)
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#define rmb() alternative("lock; addl $0,0(%%esp)", "lfence", X86_FEATURE_XMM2)
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#define wmb() alternative("lock; addl $0,0(%%esp)", "sfence", X86_FEATURE_XMM)
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#else /* CONFIG_X86_32 */
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#define mb() asm volatile("mfence" : : : "memory")
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#define rmb() asm volatile("lfence" : : : "memory")
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#define wmb() asm volatile("sfence" : : : "memory")
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#endif /* CONFIG_X86_32 */
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#ifdef CONFIG_SMP
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#define smp_mb() mb()
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#ifdef CONFIG_X86_PPRO_FENCE
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#define smp_rmb() rmb()
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#else /* CONFIG_X86_PPRO_FENCE */
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#define smp_rmb() barrier()
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#endif /* CONFIG_X86_PPRO_FENCE */
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#define smp_wmb() barrier()
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#define set_mb(var, value) do { (void)xchg(&var, value); } while (0)
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#else /* CONFIG_SMP */
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#define smp_mb() barrier()
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#define smp_rmb() barrier()
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#define smp_wmb() barrier()
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#define set_mb(var, value) do { var = value; barrier(); } while (0)
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#endif /* CONFIG_SMP */
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#define read_barrier_depends() do { } while (0)
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#define smp_read_barrier_depends() do { } while (0)
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/*
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* Stop RDTSC speculation. This is needed when you need to use RDTSC
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* (or get_cycles or vread that possibly accesses the TSC) in a defined
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* code region.
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*
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* (Could use an alternative three way for this if there was one.)
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*/
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static inline void rdtsc_barrier(void)
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{
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alternative(ASM_NOP3, "mfence", X86_FEATURE_MFENCE_RDTSC);
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alternative(ASM_NOP3, "lfence", X86_FEATURE_LFENCE_RDTSC);
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}
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#endif
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