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