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 #define read_barrier_depends() do { } while (0)
33
34 #ifdef CONFIG_SMP
35
36 #define smp_mb() mb()
37 #ifdef CONFIG_X86_PPRO_FENCE
38 #define smp_rmb() rmb()
39 #else /* CONFIG_X86_PPRO_FENCE */
40 #define smp_rmb() barrier()
41 #endif /* CONFIG_X86_PPRO_FENCE */
42
43 #ifdef CONFIG_X86_OOSTORE
44 #define smp_wmb() wmb()
45 #else /* CONFIG_X86_OOSTORE */
46 #define smp_wmb() barrier()
47 #endif /* CONFIG_X86_OOSTORE */
48
49 #define smp_read_barrier_depends() read_barrier_depends()
50 #define set_mb(var, value) do { (void)xchg(&var, value); } while (0)
51
52 #else /* CONFIG_SMP */
53
54 #define smp_mb() barrier()
55 #define smp_rmb() barrier()
56 #define smp_wmb() barrier()
57 #define smp_read_barrier_depends() do { } while (0)
58 #define set_mb(var, value) do { var = value; barrier(); } while (0)
59
60 #endif /* CONFIG_SMP */
61
62 /*
63 * Stop RDTSC speculation. This is needed when you need to use RDTSC
64 * (or get_cycles or vread that possibly accesses the TSC) in a defined
65 * code region.
66 *
67 * (Could use an alternative three way for this if there was one.)
68 */
rdtsc_barrier(void)69 static inline void rdtsc_barrier(void)
70 {
71 alternative(ASM_NOP3, "mfence", X86_FEATURE_MFENCE_RDTSC);
72 alternative(ASM_NOP3, "lfence", X86_FEATURE_LFENCE_RDTSC);
73 }
74
75 #endif
76