As suggested by Andrew, we can use __attribute__((weak)) to get rid of ARCH_HAVE_XTIME_LOCK
Please note I compiled, and boot tested on ia32 this patch, and it seems OK. I compiled on x86_64 and got same resulting vmlinux image. But I suspect some tools might have problems because vmlinux have its first 'weak data symbol' defined. AFAIK __attribute__((weak)) was only used on text symbols. # nm vmlinux | grep ' V ' c03b01c0 V xtime_lock [PATCH] get rid of ARCH_HAVE_XTIME_LOCK 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 <[EMAIL PROTECTED]>
--- linux-2.6.19/kernel/timer.c 2006-12-11 11:25:50.000000000 +0100 +++ linux-2.6.19-ed/kernel/timer.c 2006-12-11 11:31:30.000000000 +0100 @@ -1020,11 +1020,9 @@ 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. --- linux-2.6.19/include/linux/time.h 2006-12-11 11:34:54.000000000 +0100 +++ linux-2.6.19-ed/include/linux/time.h 2006-12-11 11:34:54.000000000 +0100 @@ -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); --- linux-2.6.19/include/asm-x86_64/vsyscall.h 2006-12-11 11:34:54.000000000 +0100 +++ linux-2.6.19-ed/include/asm-x86_64/vsyscall.h 2006-12-11 11:34:54.000000000 +0100 @@ -55,11 +55,6 @@ 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__ */
