From 2c3c1048746a4622d8c89a29670120dc8fab93c4 Mon Sep 17 00:00:00 2001 From: Daniel Baumann Date: Sun, 7 Apr 2024 20:49:45 +0200 Subject: Adding upstream version 6.1.76. Signed-off-by: Daniel Baumann --- include/vdso/helpers.h | 56 ++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 56 insertions(+) create mode 100644 include/vdso/helpers.h (limited to 'include/vdso/helpers.h') diff --git a/include/vdso/helpers.h b/include/vdso/helpers.h new file mode 100644 index 000000000..9a2af9fca --- /dev/null +++ b/include/vdso/helpers.h @@ -0,0 +1,56 @@ +/* SPDX-License-Identifier: GPL-2.0 */ +#ifndef __VDSO_HELPERS_H +#define __VDSO_HELPERS_H + +#ifndef __ASSEMBLY__ + +#include + +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 it is required otherwise the compiler can validly tear + * updates to vd[x].seq and it is possible that the value seen by the + * reader it 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 it is required otherwise the compiler can validly tear + * updates to vd[x].seq and it is possible that the value seen by the + * reader it 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 */ -- cgit v1.2.3