| Message ID | c6ff621a053127a65b70f175443578db7a0711be.1434501121.git.luto@kernel.org (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
diff --git a/arch/x86/kernel/tsc.c b/arch/x86/kernel/tsc.c index 21d6e04e3e82..451bade0d320 100644 --- a/arch/x86/kernel/tsc.c +++ b/arch/x86/kernel/tsc.c @@ -961,7 +961,7 @@ static struct clocksource clocksource_tsc; */ static cycle_t read_tsc(struct clocksource *cs) { - return (cycle_t)get_cycles(); + return (cycle_t)rdtsc_ordered(); } /*
There are two logical changes here. First, this removes a check for cpu_has_tsc. That check is unnecessary, as we don't register the TSC as a clocksource on systems that have no TSC. Second, it adds a barrier, thus preventing observable non-monotonicity. I suspect that the missing barrier was never a problem in practice because system calls themselves were heavy enough barriers to prevent user code from observing time warps due to speculation. (Without the corresponding barrier in the vDSO, however, non-monotonicity is easy to detect.) Signed-off-by: Andy Lutomirski <luto@kernel.org> --- arch/x86/kernel/tsc.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)