Current File : //usr/src/linux-headers-5.15.0-125-generic/include/vdso/helpers.h
/* 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 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 */
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