/* SPDX-License-Identifier: GPL-2.0 */ #ifndef __VDSO_HELPERS_H #define __VDSO_HELPERS_H #ifndef __ASSEMBLY__ #include <vdso/datapage.h> static __always_inline u32 vdso_read_begin(const struct vdso_data *vd) { u32 seq; while (unlikely((seq = READ_ONCE(vd->seq)) & 1)) cpu_relax(); smp_rmb(); return seq; } static __always_inline u32 vdso_read_retry(const struct vdso_data *vd, u32 start) { u32 seq; smp_rmb(); seq = READ_ONCE(vd->seq); return seq != start; } static __always_inline void vdso_write_begin(struct vdso_data *vd) { /* * WRITE_ONCE() is required otherwise the compiler can validly tear * updates to vd[x].seq and it is possible that the value seen by the * reader is inconsistent. */ WRITE_ONCE(vd[CS_HRES_COARSE].seq, vd[CS_HRES_COARSE].seq + 1); WRITE_ONCE(vd[CS_RAW].seq, vd[CS_RAW].seq + 1); smp_wmb(); } static __always_inline void vdso_write_end(struct vdso_data *vd) { smp_wmb(); /* * WRITE_ONCE() is required otherwise the compiler can validly tear * updates to vd[x].seq and it is possible that the value seen by the * reader is inconsistent. */ WRITE_ONCE(vd[CS_HRES_COARSE].seq, vd[CS_HRES_COARSE].seq + 1); WRITE_ONCE(vd[CS_RAW].seq, vd[CS_RAW].seq + 1); } #endif /* !__ASSEMBLY__ */ #endif /* __VDSO_HELPERS_H */