>From the recent 4e44f3497d41db4c3b9051c61410dee8ae4fb49c commit,
> asmlinkage long sys_time(time_t __user * tloc)
> {
> - time_t i;
> - struct timeval tv;
> + /*
> + * We read xtime.tv_sec atomically - it's updated
> + * atomically by update_wall_time(), so no need to
> + * even read-lock the xtime seqlock:
> + */
> + time_t i = xtime.tv_sec;
>
> - do_gettimeofday(&tv);
> - i = tv.tv_sec;
> + smp_rmb(); /* sys_time() results are coherent */
The is no reason to use rmb(), we don't do any LOADs which could be reordered.
What we need is a simple compiler barrier, to prevent the reading of the
"volatile" xtime.tv_sec twice.
Signed-off-by: Oleg Nesterov <[EMAIL PROTECTED]>
--- t/kernel/time.c~ 2007-06-26 16:28:59.000000000 +0400
+++ t/kernel/time.c 2007-06-26 16:32:09.000000000 +0400
@@ -64,7 +64,7 @@ asmlinkage long sys_time(time_t __user *
*/
time_t i = xtime.tv_sec;
- smp_rmb(); /* sys_time() results are coherent */
+ barrier(); /* sys_time() results are coherent */
if (tloc) {
if (put_user(i, tloc))
-
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