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Subject[patch V2 13/17] lib/vdso: Avoid highres update if clocksource is not VDSO capable
From: Thomas Gleixner <tglx@linutronix.de>

If the current clocksource is not VDSO capable there is no point in
updating the high resolution parts of the VDSO data.

Replace the architecture specific check with a check for a VDSO capable
clocksource and skip the update if there is none.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
---
arch/arm/include/asm/vdso/vsyscall.h | 7 -------
include/asm-generic/vdso/vsyscall.h | 7 -------
kernel/time/vsyscall.c | 6 +++---
3 files changed, 3 insertions(+), 17 deletions(-)

--- a/arch/arm/include/asm/vdso/vsyscall.h
+++ b/arch/arm/include/asm/vdso/vsyscall.h
@@ -22,13 +22,6 @@ struct vdso_data *__arm_get_k_vdso_data(
#define __arch_get_k_vdso_data __arm_get_k_vdso_data

static __always_inline
-bool __arm_update_vdso_data(void)
-{
- return cntvct_ok;
-}
-#define __arch_update_vdso_data __arm_update_vdso_data
-
-static __always_inline
void __arm_sync_vdso_data(struct vdso_data *vdata)
{
flush_dcache_page(virt_to_page(vdata));
--- a/include/asm-generic/vdso/vsyscall.h
+++ b/include/asm-generic/vdso/vsyscall.h
@@ -11,13 +11,6 @@ static __always_inline struct vdso_data
}
#endif /* __arch_get_k_vdso_data */

-#ifndef __arch_update_vdso_data
-static __always_inline bool __arch_update_vdso_data(void)
-{
- return true;
-}
-#endif /* __arch_update_vdso_data */
-
#ifndef __arch_update_vsyscall
static __always_inline void __arch_update_vsyscall(struct vdso_data *vdata,
struct timekeeper *tk)
--- a/kernel/time/vsyscall.c
+++ b/kernel/time/vsyscall.c
@@ -105,10 +105,10 @@ void update_vsyscall(struct timekeeper *
WRITE_ONCE(vdata[CS_HRES_COARSE].hrtimer_res, hrtimer_resolution);

/*
- * Architectures can opt out of updating the high resolution part
- * of the VDSO.
+ * If the current clocksource is not VDSO capable, then spare the
+ * update of the high reolution parts.
*/
- if (__arch_update_vdso_data())
+ if (clock_mode != VDSO_CLOCKMODE_NONE)
update_vdso_data(vdata, tk);

__arch_update_vsyscall(vdata, tk);
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