mirror of
https://github.com/torvalds/linux.git
synced 2026-04-18 06:44:00 -04:00
8bd49acb4e
The usage of cpu_relax() requires vdso/processor.h. Currently this header is included transitively, but that transitive inclusion is about to go away. Explicitly include the header. Signed-off-by: Thomas Weißschuh <thomas.weissschuh@linutronix.de> Signed-off-by: Thomas Gleixner <tglx@kernel.org> Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de> Link: https://patch.msgid.link/20260227-vdso-header-cleanups-v2-11-35d60acf7410@linutronix.de
117 lines
3.0 KiB
C
117 lines
3.0 KiB
C
/* SPDX-License-Identifier: GPL-2.0 */
|
|
#ifndef __VDSO_HELPERS_H
|
|
#define __VDSO_HELPERS_H
|
|
|
|
#ifndef __ASSEMBLY__
|
|
|
|
#include <asm/barrier.h>
|
|
#include <vdso/datapage.h>
|
|
#include <vdso/processor.h>
|
|
#include <vdso/clocksource.h>
|
|
|
|
static __always_inline bool vdso_is_timens_clock(const struct vdso_clock *vc)
|
|
{
|
|
return IS_ENABLED(CONFIG_TIME_NS) && vc->clock_mode == VDSO_CLOCKMODE_TIMENS;
|
|
}
|
|
|
|
static __always_inline u32 vdso_read_begin(const struct vdso_clock *vc)
|
|
{
|
|
u32 seq;
|
|
|
|
while (unlikely((seq = READ_ONCE(vc->seq)) & 1))
|
|
cpu_relax();
|
|
|
|
smp_rmb();
|
|
return seq;
|
|
}
|
|
|
|
/*
|
|
* Variant of vdso_read_begin() to handle VDSO_CLOCKMODE_TIMENS.
|
|
*
|
|
* Time namespace enabled tasks have a special VVAR page installed which has
|
|
* vc->seq set to 1 and vc->clock_mode set to VDSO_CLOCKMODE_TIMENS. For non
|
|
* time namespace affected tasks this does not affect performance because if
|
|
* vc->seq is odd, i.e. a concurrent update is in progress the extra check for
|
|
* vc->clock_mode is just a few extra instructions while spin waiting for
|
|
* vc->seq to become even again.
|
|
*/
|
|
static __always_inline bool vdso_read_begin_timens(const struct vdso_clock *vc, u32 *seq)
|
|
{
|
|
while (unlikely((*seq = READ_ONCE(vc->seq)) & 1)) {
|
|
if (vdso_is_timens_clock(vc))
|
|
return true;
|
|
cpu_relax();
|
|
}
|
|
smp_rmb();
|
|
|
|
return false;
|
|
}
|
|
|
|
static __always_inline u32 vdso_read_retry(const struct vdso_clock *vc,
|
|
u32 start)
|
|
{
|
|
u32 seq;
|
|
|
|
smp_rmb();
|
|
seq = READ_ONCE(vc->seq);
|
|
return unlikely(seq != start);
|
|
}
|
|
|
|
static __always_inline void vdso_write_seq_begin(struct vdso_clock *vc)
|
|
{
|
|
/*
|
|
* WRITE_ONCE() is required otherwise the compiler can validly tear
|
|
* updates to vc->seq and it is possible that the value seen by the
|
|
* reader is inconsistent.
|
|
*/
|
|
WRITE_ONCE(vc->seq, vc->seq + 1);
|
|
}
|
|
|
|
static __always_inline void vdso_write_seq_end(struct vdso_clock *vc)
|
|
{
|
|
/*
|
|
* WRITE_ONCE() is required otherwise the compiler can validly tear
|
|
* updates to vc->seq and it is possible that the value seen by the
|
|
* reader is inconsistent.
|
|
*/
|
|
WRITE_ONCE(vc->seq, vc->seq + 1);
|
|
}
|
|
|
|
static __always_inline void vdso_write_begin_clock(struct vdso_clock *vc)
|
|
{
|
|
vdso_write_seq_begin(vc);
|
|
/* Ensure the sequence invalidation is visible before data is modified */
|
|
smp_wmb();
|
|
}
|
|
|
|
static __always_inline void vdso_write_end_clock(struct vdso_clock *vc)
|
|
{
|
|
/* Ensure the data update is visible before the sequence is set valid again */
|
|
smp_wmb();
|
|
vdso_write_seq_end(vc);
|
|
}
|
|
|
|
static __always_inline void vdso_write_begin(struct vdso_time_data *vd)
|
|
{
|
|
struct vdso_clock *vc = vd->clock_data;
|
|
|
|
vdso_write_seq_begin(&vc[CS_HRES_COARSE]);
|
|
vdso_write_seq_begin(&vc[CS_RAW]);
|
|
/* Ensure the sequence invalidation is visible before data is modified */
|
|
smp_wmb();
|
|
}
|
|
|
|
static __always_inline void vdso_write_end(struct vdso_time_data *vd)
|
|
{
|
|
struct vdso_clock *vc = vd->clock_data;
|
|
|
|
/* Ensure the data update is visible before the sequence is set valid again */
|
|
smp_wmb();
|
|
vdso_write_seq_end(&vc[CS_HRES_COARSE]);
|
|
vdso_write_seq_end(&vc[CS_RAW]);
|
|
}
|
|
|
|
#endif /* !__ASSEMBLY__ */
|
|
|
|
#endif /* __VDSO_HELPERS_H */
|