From: Eric Dumazet ARCH_HAVE_XTIME_LOCK is used by x86_64 arch . This arch needs to place a read only copy of xtime_lock into vsyscall page. This read only copy is named __xtime_lock, and xtime_lock is defined in arch/x86_64/kernel/vmlinux.lds.S as an alias. So the declaration of xtime_lock in kernel/timer.c was guarded by ARCH_HAVE_XTIME_LOCK define, defined to true on x86_64. We can get same result with _attribute__((weak)) in the declaration. linker should do the job. Signed-off-by: Eric Dumazet Cc: Andi Kleen Signed-off-by: Andrew Morton --- include/asm-x86_64/vsyscall.h | 5 ----- include/linux/time.h | 2 +- kernel/timer.c | 4 +--- 3 files changed, 2 insertions(+), 9 deletions(-) diff -puN include/asm-x86_64/vsyscall.h~get-rid-of-arch_have_xtime_lock include/asm-x86_64/vsyscall.h --- a/include/asm-x86_64/vsyscall.h~get-rid-of-arch_have_xtime_lock +++ a/include/asm-x86_64/vsyscall.h @@ -56,11 +56,6 @@ extern struct vxtime_data vxtime; extern int vgetcpu_mode; extern struct timezone sys_tz; extern int sysctl_vsyscall; -extern seqlock_t xtime_lock; - -extern int sysctl_vsyscall; - -#define ARCH_HAVE_XTIME_LOCK 1 #endif /* __KERNEL__ */ diff -puN include/linux/time.h~get-rid-of-arch_have_xtime_lock include/linux/time.h --- a/include/linux/time.h~get-rid-of-arch_have_xtime_lock +++ a/include/linux/time.h @@ -90,7 +90,7 @@ static inline struct timespec timespec_s extern struct timespec xtime; extern struct timespec wall_to_monotonic; -extern seqlock_t xtime_lock; +extern seqlock_t xtime_lock __attribute__((weak)); void timekeeping_init(void); diff -puN kernel/timer.c~get-rid-of-arch_have_xtime_lock kernel/timer.c --- a/kernel/timer.c~get-rid-of-arch_have_xtime_lock +++ a/kernel/timer.c @@ -1162,11 +1162,9 @@ static inline void calc_load(unsigned lo * This read-write spinlock protects us from races in SMP while * playing with xtime and avenrun. */ -#ifndef ARCH_HAVE_XTIME_LOCK -__cacheline_aligned_in_smp DEFINE_SEQLOCK(xtime_lock); +__attribute__((weak)) __cacheline_aligned_in_smp DEFINE_SEQLOCK(xtime_lock); EXPORT_SYMBOL(xtime_lock); -#endif /* * This function runs timers and the timer-tq in bottom half context. _