LinuxQuestions.org - What is CONFIG_GENERIC_TIME

It is only used once in linux-stable, in ./include/linux/clocksource.h.

Code:

#ifdef CONFIG_GENERIC_TIME_VSYSCALL

extern void

update_vsyscall(struct timespec *ts, struct timespec *wtm,

            struct clocksource *c, u32 mult);

extern void update_vsyscall_tz(void);

#else

static inline void

update_vsyscall(struct timespec *ts, struct timespec *wtm,

            struct clocksource *c, u32 mult)

{

}



static inline void update_vsyscall_tz(void)

{

}

#endif

So obviously, if you don't have it defined, those functions do nothing.

On my system, those externs are defined in ./arch/x86/kernel/vsyscall_64.c. Have a look.