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