1 /* SPDX-License-Identifier: GPL-2.0 */ 1 /* SPDX-License-Identifier: GPL-2.0 */
2 #ifndef __VDSO_HELPERS_H 2 #ifndef __VDSO_HELPERS_H
3 #define __VDSO_HELPERS_H 3 #define __VDSO_HELPERS_H
4 4
5 #ifndef __ASSEMBLY__ 5 #ifndef __ASSEMBLY__
6 6
7 #include <asm/barrier.h> <<
8 #include <vdso/datapage.h> 7 #include <vdso/datapage.h>
9 8
10 static __always_inline u32 vdso_read_begin(con 9 static __always_inline u32 vdso_read_begin(const struct vdso_data *vd)
11 { 10 {
12 u32 seq; 11 u32 seq;
13 12
14 while (unlikely((seq = READ_ONCE(vd->s !! 13 while ((seq = READ_ONCE(vd->seq)) & 1)
15 cpu_relax(); 14 cpu_relax();
16 15
17 smp_rmb(); 16 smp_rmb();
18 return seq; 17 return seq;
19 } 18 }
20 19
21 static __always_inline u32 vdso_read_retry(con 20 static __always_inline u32 vdso_read_retry(const struct vdso_data *vd,
22 u32 21 u32 start)
23 { 22 {
24 u32 seq; 23 u32 seq;
25 24
26 smp_rmb(); 25 smp_rmb();
27 seq = READ_ONCE(vd->seq); 26 seq = READ_ONCE(vd->seq);
28 return seq != start; 27 return seq != start;
29 } 28 }
30 29
31 static __always_inline void vdso_write_begin(s 30 static __always_inline void vdso_write_begin(struct vdso_data *vd)
32 { 31 {
33 /* 32 /*
34 * WRITE_ONCE() is required otherwise !! 33 * WRITE_ONCE it is required otherwise the compiler can validly tear
35 * updates to vd[x].seq and it is poss 34 * updates to vd[x].seq and it is possible that the value seen by the
36 * reader is inconsistent. !! 35 * reader it is inconsistent.
37 */ 36 */
38 WRITE_ONCE(vd[CS_HRES_COARSE].seq, vd[ 37 WRITE_ONCE(vd[CS_HRES_COARSE].seq, vd[CS_HRES_COARSE].seq + 1);
39 WRITE_ONCE(vd[CS_RAW].seq, vd[CS_RAW]. 38 WRITE_ONCE(vd[CS_RAW].seq, vd[CS_RAW].seq + 1);
40 smp_wmb(); 39 smp_wmb();
41 } 40 }
42 41
43 static __always_inline void vdso_write_end(str 42 static __always_inline void vdso_write_end(struct vdso_data *vd)
44 { 43 {
45 smp_wmb(); 44 smp_wmb();
46 /* 45 /*
47 * WRITE_ONCE() is required otherwise !! 46 * WRITE_ONCE it is required otherwise the compiler can validly tear
48 * updates to vd[x].seq and it is poss 47 * updates to vd[x].seq and it is possible that the value seen by the
49 * reader is inconsistent. !! 48 * reader it is inconsistent.
50 */ 49 */
51 WRITE_ONCE(vd[CS_HRES_COARSE].seq, vd[ 50 WRITE_ONCE(vd[CS_HRES_COARSE].seq, vd[CS_HRES_COARSE].seq + 1);
52 WRITE_ONCE(vd[CS_RAW].seq, vd[CS_RAW]. 51 WRITE_ONCE(vd[CS_RAW].seq, vd[CS_RAW].seq + 1);
53 } 52 }
54 53
55 #endif /* !__ASSEMBLY__ */ 54 #endif /* !__ASSEMBLY__ */
56 55
57 #endif /* __VDSO_HELPERS_H */ 56 #endif /* __VDSO_HELPERS_H */
58 57
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