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https://git.kernel.org/pub/scm/linux/kernel/git/chenhuacai/linux-loongson
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ad64d71d74
Auxiliary clocks will have their vDSO data in a dedicated 'struct vdso_clock', which needs to be synchronized independently. Add a helper to synchronize a single vDSO clock. [ tglx: Move the SMP memory barriers to the call sites and get rid of the confusing first/last arguments and conditional barriers ] Signed-off-by: Thomas Weißschuh <thomas.weissschuh@linutronix.de> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Link: https://lore.kernel.org/all/20250701-vdso-auxclock-v1-4-df7d9f87b9b8@linutronix.de
88 lines
2.1 KiB
C
88 lines
2.1 KiB
C
/* SPDX-License-Identifier: GPL-2.0 */
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#ifndef __VDSO_HELPERS_H
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#define __VDSO_HELPERS_H
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#ifndef __ASSEMBLY__
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#include <asm/barrier.h>
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#include <vdso/datapage.h>
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static __always_inline u32 vdso_read_begin(const struct vdso_clock *vc)
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{
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u32 seq;
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while (unlikely((seq = READ_ONCE(vc->seq)) & 1))
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cpu_relax();
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smp_rmb();
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return seq;
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}
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static __always_inline u32 vdso_read_retry(const struct vdso_clock *vc,
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u32 start)
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{
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u32 seq;
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smp_rmb();
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seq = READ_ONCE(vc->seq);
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return seq != start;
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}
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static __always_inline void vdso_write_seq_begin(struct vdso_clock *vc)
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{
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/*
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* WRITE_ONCE() is required otherwise the compiler can validly tear
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* updates to vc->seq and it is possible that the value seen by the
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* reader is inconsistent.
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*/
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WRITE_ONCE(vc->seq, vc->seq + 1);
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}
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static __always_inline void vdso_write_seq_end(struct vdso_clock *vc)
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{
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/*
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* WRITE_ONCE() is required otherwise the compiler can validly tear
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* updates to vc->seq and it is possible that the value seen by the
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* reader is inconsistent.
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*/
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WRITE_ONCE(vc->seq, vc->seq + 1);
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}
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static __always_inline void vdso_write_begin_clock(struct vdso_clock *vc)
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{
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vdso_write_seq_begin(vc);
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/* Ensure the sequence invalidation is visible before data is modified */
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smp_wmb();
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}
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static __always_inline void vdso_write_end_clock(struct vdso_clock *vc)
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{
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/* Ensure the data update is visible before the sequence is set valid again */
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smp_wmb();
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vdso_write_seq_end(vc);
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}
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static __always_inline void vdso_write_begin(struct vdso_time_data *vd)
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{
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struct vdso_clock *vc = vd->clock_data;
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vdso_write_seq_begin(&vc[CS_HRES_COARSE]);
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vdso_write_seq_begin(&vc[CS_RAW]);
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/* Ensure the sequence invalidation is visible before data is modified */
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smp_wmb();
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}
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static __always_inline void vdso_write_end(struct vdso_time_data *vd)
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{
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struct vdso_clock *vc = vd->clock_data;
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/* Ensure the data update is visible before the sequence is set valid again */
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smp_wmb();
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vdso_write_seq_end(&vc[CS_HRES_COARSE]);
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vdso_write_seq_end(&vc[CS_RAW]);
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}
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#endif /* !__ASSEMBLY__ */
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#endif /* __VDSO_HELPERS_H */
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