git
/
linux
mirror of https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
1
0
Fork 0
Code Issues Packages Projects Releases Wiki Activity

vdso/helpers: Add helpers for seqlocks of single vdso_clock 

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
This commit is contained in:
Thomas Weißschuh 2025-07-01 10:57:58 +02:00 committed by Thomas Gleixner
parent 76164ca0d1
commit ad64d71d74
1 changed files with 40 additions and 14 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

54
include/vdso/helpers.h
View File

@ -28,17 +28,47 @@ static __always_inline u32 vdso_read_retry(const struct vdso_clock *vc,
return 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;
/*
* WRITE_ONCE() is required otherwise the compiler can validly tear
* updates to vd[x].seq and it is possible that the value seen by the
* reader is inconsistent.
*/
WRITE_ONCE(vc[CS_HRES_COARSE].seq, vc[CS_HRES_COARSE].seq + 1);
WRITE_ONCE(vc[CS_RAW].seq, vc[CS_RAW].seq + 1);
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();
}
@ -46,14 +76,10 @@ 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();
/*
* WRITE_ONCE() is required otherwise the compiler can validly tear
* updates to vd[x].seq and it is possible that the value seen by the
* reader is inconsistent.
*/
WRITE_ONCE(vc[CS_HRES_COARSE].seq, vc[CS_HRES_COARSE].seq + 1);
WRITE_ONCE(vc[CS_RAW].seq, vc[CS_RAW].seq + 1);
vdso_write_seq_end(&vc[CS_HRES_COARSE]);
vdso_write_seq_end(&vc[CS_RAW]);
}
#endif /* !__ASSEMBLY__ */