x86_64 : fix vtime() vsyscall
PATCH 1/1 x86_64 : fix vtime() vsyscall
There is a tiny probability that the return value from vtime(time_t *t) is 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 +5 -5
@@ -147,15 +147,15 @@ int __vsyscall(0) vgettimeofday(struct treturn 0 ; } -/* This will break when the xtime seconds get inaccurate, but that is -* unlikely */ time_t __vsyscall(1) vtime(time_t *t) { +time_t result;if (!__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.