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Message-ID: <171258184409.10875.16644898278425182282.tip-bot2@tip-bot2>
Date: Mon, 08 Apr 2024 13:10:44 -0000
From: "tip-bot2 for Adrian Hunter" <tip-bot2@...utronix.de>
To: linux-tip-commits@...r.kernel.org
Cc: Thomas Gleixner <tglx@...utronix.de>,
Adrian Hunter <adrian.hunter@...el.com>, x86@...nel.org,
linux-kernel@...r.kernel.org
Subject: [tip: timers/core] vdso: Consolidate nanoseconds calculation
The following commit has been merged into the timers/core branch of tip:
Commit-ID: 5b26ef660a690e424d9548fdf0565d4172d5d88f
Gitweb: https://git.kernel.org/tip/5b26ef660a690e424d9548fdf0565d4172d5d88f
Author: Adrian Hunter <adrian.hunter@...el.com>
AuthorDate: Mon, 25 Mar 2024 08:40:06 +02:00
Committer: Thomas Gleixner <tglx@...utronix.de>
CommitterDate: Mon, 08 Apr 2024 15:03:06 +02:00
vdso: Consolidate nanoseconds calculation
Consolidate nanoseconds calculation to simplify and reduce code
duplication.
Suggested-by: Thomas Gleixner <tglx@...utronix.de>
Signed-off-by: Adrian Hunter <adrian.hunter@...el.com>
Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
Link: https://lore.kernel.org/r/20240325064023.2997-3-adrian.hunter@intel.com
---
arch/x86/include/asm/vdso/gettimeofday.h | 17 ++++-----
lib/vdso/gettimeofday.c | 43 ++++++++++-------------
2 files changed, 27 insertions(+), 33 deletions(-)
diff --git a/arch/x86/include/asm/vdso/gettimeofday.h b/arch/x86/include/asm/vdso/gettimeofday.h
index 8e048ca..5727ded 100644
--- a/arch/x86/include/asm/vdso/gettimeofday.h
+++ b/arch/x86/include/asm/vdso/gettimeofday.h
@@ -300,7 +300,7 @@ static inline bool arch_vdso_cycles_ok(u64 cycles)
#define vdso_cycles_ok arch_vdso_cycles_ok
/*
- * x86 specific delta calculation.
+ * x86 specific calculation of nanoseconds for the current cycle count
*
* The regular implementation assumes that clocksource reads are globally
* monotonic. The TSC can be slightly off across sockets which can cause
@@ -308,8 +308,8 @@ static inline bool arch_vdso_cycles_ok(u64 cycles)
* jump.
*
* Therefore it needs to be verified that @cycles are greater than
- * @last. If not then use @last, which is the base time of the current
- * conversion period.
+ * @vd->cycles_last. If not then use @vd->cycles_last, which is the base
+ * time of the current conversion period.
*
* This variant also uses a custom mask because while the clocksource mask of
* all the VDSO capable clocksources on x86 is U64_MAX, the above code uses
@@ -317,25 +317,24 @@ static inline bool arch_vdso_cycles_ok(u64 cycles)
* declares everything with the MSB/Sign-bit set as invalid. Therefore the
* effective mask is S64_MAX.
*/
-static __always_inline
-u64 vdso_calc_delta(u64 cycles, u64 last, u64 mask, u32 mult)
+static __always_inline u64 vdso_calc_ns(const struct vdso_data *vd, u64 cycles, u64 base)
{
/*
* Due to the MSB/Sign-bit being used as invalid marker (see
* arch_vdso_cycles_valid() above), the effective mask is S64_MAX.
*/
- u64 delta = (cycles - last) & S64_MAX;
+ u64 delta = (cycles - vd->cycle_last) & S64_MAX;
/*
* Due to the above mentioned TSC wobbles, filter out negative motion.
* Per the above masking, the effective sign bit is now bit 62.
*/
if (unlikely(delta & (1ULL << 62)))
- return 0;
+ return base >> vd->shift;
- return delta * mult;
+ return ((delta * vd->mult) + base) >> vd->shift;
}
-#define vdso_calc_delta vdso_calc_delta
+#define vdso_calc_ns vdso_calc_ns
#endif /* !__ASSEMBLY__ */
diff --git a/lib/vdso/gettimeofday.c b/lib/vdso/gettimeofday.c
index faccf12..9fa90e0 100644
--- a/lib/vdso/gettimeofday.c
+++ b/lib/vdso/gettimeofday.c
@@ -5,31 +5,32 @@
#include <vdso/datapage.h>
#include <vdso/helpers.h>
-#ifndef vdso_calc_delta
+#ifndef vdso_calc_ns
#ifdef VDSO_DELTA_NOMASK
-# define VDSO_DELTA_MASK(mask) U64_MAX
+# define VDSO_DELTA_MASK(vd) U64_MAX
#else
-# define VDSO_DELTA_MASK(mask) (mask)
+# define VDSO_DELTA_MASK(vd) (vd->mask)
+#endif
+
+#ifndef vdso_shift_ns
+static __always_inline u64 vdso_shift_ns(u64 ns, u32 shift)
+{
+ return ns >> shift;
+}
#endif
/*
* Default implementation which works for all sane clocksources. That
* obviously excludes x86/TSC.
*/
-static __always_inline
-u64 vdso_calc_delta(u64 cycles, u64 last, u64 mask, u32 mult)
+static __always_inline u64 vdso_calc_ns(const struct vdso_data *vd, u64 cycles, u64 base)
{
- return ((cycles - last) & VDSO_DELTA_MASK(mask)) * mult;
-}
-#endif
+ u64 delta = (cycles - vd->cycle_last) & VDSO_DELTA_MASK(vd);
-#ifndef vdso_shift_ns
-static __always_inline u64 vdso_shift_ns(u64 ns, u32 shift)
-{
- return ns >> shift;
+ return vdso_shift_ns((delta * vd->mult) + base, vd->shift);
}
-#endif
+#endif /* vdso_calc_ns */
#ifndef __arch_vdso_hres_capable
static inline bool __arch_vdso_hres_capable(void)
@@ -56,10 +57,10 @@ static inline bool vdso_cycles_ok(u64 cycles)
static __always_inline int do_hres_timens(const struct vdso_data *vdns, clockid_t clk,
struct __kernel_timespec *ts)
{
- const struct vdso_data *vd;
const struct timens_offset *offs = &vdns->offset[clk];
const struct vdso_timestamp *vdso_ts;
- u64 cycles, last, ns;
+ const struct vdso_data *vd;
+ u64 cycles, ns;
u32 seq;
s64 sec;
@@ -80,10 +81,7 @@ static __always_inline int do_hres_timens(const struct vdso_data *vdns, clockid_
cycles = __arch_get_hw_counter(vd->clock_mode, vd);
if (unlikely(!vdso_cycles_ok(cycles)))
return -1;
- ns = vdso_ts->nsec;
- last = vd->cycle_last;
- ns += vdso_calc_delta(cycles, last, vd->mask, vd->mult);
- ns = vdso_shift_ns(ns, vd->shift);
+ ns = vdso_calc_ns(vd, cycles, vdso_ts->nsec);
sec = vdso_ts->sec;
} while (unlikely(vdso_read_retry(vd, seq)));
@@ -118,7 +116,7 @@ static __always_inline int do_hres(const struct vdso_data *vd, clockid_t clk,
struct __kernel_timespec *ts)
{
const struct vdso_timestamp *vdso_ts = &vd->basetime[clk];
- u64 cycles, last, sec, ns;
+ u64 cycles, sec, ns;
u32 seq;
/* Allows to compile the high resolution parts out */
@@ -151,10 +149,7 @@ static __always_inline int do_hres(const struct vdso_data *vd, clockid_t clk,
cycles = __arch_get_hw_counter(vd->clock_mode, vd);
if (unlikely(!vdso_cycles_ok(cycles)))
return -1;
- ns = vdso_ts->nsec;
- last = vd->cycle_last;
- ns += vdso_calc_delta(cycles, last, vd->mask, vd->mult);
- ns = vdso_shift_ns(ns, vd->shift);
+ ns = vdso_calc_ns(vd, cycles, vdso_ts->nsec);
sec = vdso_ts->sec;
} while (unlikely(vdso_read_retry(vd, seq)));
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