fix vtime() vsyscall From: Eric Dumazet There is a tiny probability that the return value from vtime(time_t *t) is Signed-off-by: Andi Kleen 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 --- 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.