1 #ifndef _ASM_UM_BARRIER_H_ 2 #define _ASM_UM_BARRIER_H_ 3 4 #include <asm/asm.h> 5 #include <asm/segment.h> 6 #include <asm/cpufeature.h> 7 #include <asm/cmpxchg.h> 8 #include <asm/nops.h> 9 10 #include <linux/kernel.h> 11 #include <linux/irqflags.h> 12 13 /* 14 * Force strict CPU ordering. 15 * And yes, this is required on UP too when we're talking 16 * to devices. 17 */ 18 #ifdef CONFIG_X86_32 19 20 #define mb() alternative("lock; addl $0,0(%%esp)", "mfence", X86_FEATURE_XMM2) 21 #define rmb() alternative("lock; addl $0,0(%%esp)", "lfence", X86_FEATURE_XMM2) 22 #define wmb() alternative("lock; addl $0,0(%%esp)", "sfence", X86_FEATURE_XMM) 23 24 #else /* CONFIG_X86_32 */ 25 26 #define mb() asm volatile("mfence" : : : "memory") 27 #define rmb() asm volatile("lfence" : : : "memory") 28 #define wmb() asm volatile("sfence" : : : "memory") 29 30 #endif /* CONFIG_X86_32 */ 31 32 #ifdef CONFIG_X86_PPRO_FENCE 33 #define dma_rmb() rmb() 34 #else /* CONFIG_X86_PPRO_FENCE */ 35 #define dma_rmb() barrier() 36 #endif /* CONFIG_X86_PPRO_FENCE */ 37 #define dma_wmb() barrier() 38 39 #define smp_mb() barrier() 40 #define smp_rmb() barrier() 41 #define smp_wmb() barrier() 42 #define set_mb(var, value) do { var = value; barrier(); } while (0) 43 44 #define read_barrier_depends() do { } while (0) 45 #define smp_read_barrier_depends() do { } while (0) 46 47 /* 48 * Stop RDTSC speculation. This is needed when you need to use RDTSC 49 * (or get_cycles or vread that possibly accesses the TSC) in a defined 50 * code region. 51 * 52 * (Could use an alternative three way for this if there was one.) 53 */ 54 static inline void rdtsc_barrier(void) 55 { 56 alternative_2("", "mfence", X86_FEATURE_MFENCE_RDTSC, 57 "lfence", X86_FEATURE_LFENCE_RDTSC); 58 } 59 60 #endif 61