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1/* SPDX-License-Identifier: GPL-2.0 */2#ifndef __VDSO_HELPERS_H3#define __VDSO_HELPERS_H4 5#ifndef __ASSEMBLY__6 7#include <asm/barrier.h>8#include <vdso/datapage.h>9 10static __always_inline u32 vdso_read_begin(const struct vdso_data *vd)11{12 u32 seq;13 14 while (unlikely((seq = READ_ONCE(vd->seq)) & 1))15 cpu_relax();16 17 smp_rmb();18 return seq;19}20 21static __always_inline u32 vdso_read_retry(const struct vdso_data *vd,22 u32 start)23{24 u32 seq;25 26 smp_rmb();27 seq = READ_ONCE(vd->seq);28 return seq != start;29}30 31static __always_inline void vdso_write_begin(struct vdso_data *vd)32{33 /*34 * WRITE_ONCE() is required otherwise the compiler can validly tear35 * updates to vd[x].seq and it is possible that the value seen by the36 * reader is inconsistent.37 */38 WRITE_ONCE(vd[CS_HRES_COARSE].seq, vd[CS_HRES_COARSE].seq + 1);39 WRITE_ONCE(vd[CS_RAW].seq, vd[CS_RAW].seq + 1);40 smp_wmb();41}42 43static __always_inline void vdso_write_end(struct vdso_data *vd)44{45 smp_wmb();46 /*47 * WRITE_ONCE() is required otherwise the compiler can validly tear48 * updates to vd[x].seq and it is possible that the value seen by the49 * reader is inconsistent.50 */51 WRITE_ONCE(vd[CS_HRES_COARSE].seq, vd[CS_HRES_COARSE].seq + 1);52 WRITE_ONCE(vd[CS_RAW].seq, vd[CS_RAW].seq + 1);53}54 55#endif /* !__ASSEMBLY__ */56 57#endif /* __VDSO_HELPERS_H */58