From: Eric Dumazet <[email protected]>
There is a tiny probability that the return value from vtime(time_t *t) is
Signed-off-by: Andi Kleen <[email protected]>
different than the value stored in *t
Using a temporary variable solves the problem and gives a faster code.
17: 48 85 ff test %rdi,%rdi
1a: 48 8b 05 00 00 00 00 mov 0(%rip),%rax #
__vsyscall_gtod_data.wall_time_tv.tv_sec
21: 74 03 je 26
23: 48 89 07 mov %rax,(%rdi)
26: c9 leaveq
27: c3 retq
Signed-off-by: Eric Dumazet <[email protected]>
---
arch/x86_64/kernel/vsyscall.c | 8 +++++---
1 file changed, 5 insertions(+), 3 deletions(-)
Index: linux/arch/x86_64/kernel/vsyscall.c
===================================================================
--- linux.orig/arch/x86_64/kernel/vsyscall.c
+++ linux/arch/x86_64/kernel/vsyscall.c
@@ -156,11 +156,13 @@ int __vsyscall(0) vgettimeofday(struct t
* unlikely */
time_t __vsyscall(1) vtime(time_t *t)
{
+ time_t result;
if (unlikely(!__vsyscall_gtod_data.sysctl_enabled))
return time_syscall(t);
- else if (t)
- *t = __vsyscall_gtod_data.wall_time_tv.tv_sec;
- return __vsyscall_gtod_data.wall_time_tv.tv_sec;
+ result = __vsyscall_gtod_data.wall_time_tv.tv_sec;
+ if (t)
+ *t = result;
+ return result;
}
/* Fast way to get current CPU and node.
-
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