From: Eric Dumazet <[email protected]>
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]>
Signed-off-by: Andi Kleen <[email protected]>
Cc: Andi Kleen <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
---
include/asm-x86_64/vsyscall.h | 5 -----
include/linux/time.h | 2 +-
kernel/timer.c | 4 +---
3 files changed, 2 insertions(+), 9 deletions(-)
Index: linux/include/asm-x86_64/vsyscall.h
===================================================================
--- linux.orig/include/asm-x86_64/vsyscall.h
+++ linux/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__ */
Index: linux/include/linux/time.h
===================================================================
--- linux.orig/include/linux/time.h
+++ linux/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);
Index: linux/kernel/timer.c
===================================================================
--- linux.orig/kernel/timer.c
+++ linux/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.
-
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