From cb9e35dce94a1b9c59d46224e8a94377d673e204 Mon Sep 17 00:00:00 2001 From: Ingo Molnar Date: Sat, 8 Nov 2008 20:27:00 +0100 Subject: x86: clean up rdtsc_barrier() use Impact: cleanup Move rdtsc_barrier() use to vsyscall_64.c where it's relied on, and point out its role in the context of its use. Signed-off-by: Ingo Molnar --- arch/x86/kernel/vsyscall_64.c | 9 +++++++++ 1 file changed, 9 insertions(+) (limited to 'arch/x86/kernel/vsyscall_64.c') diff --git a/arch/x86/kernel/vsyscall_64.c b/arch/x86/kernel/vsyscall_64.c index 0b8b6690a86d..ebf2f12900f5 100644 --- a/arch/x86/kernel/vsyscall_64.c +++ b/arch/x86/kernel/vsyscall_64.c @@ -128,7 +128,16 @@ static __always_inline void do_vgettimeofday(struct timeval * tv) gettimeofday(tv,NULL); return; } + + /* + * Surround the RDTSC by barriers, to make sure it's not + * speculated to outside the seqlock critical section and + * does not cause time warps: + */ + rdtsc_barrier(); now = vread(); + rdtsc_barrier(); + base = __vsyscall_gtod_data.clock.cycle_last; mask = __vsyscall_gtod_data.clock.mask; mult = __vsyscall_gtod_data.clock.mult; -- cgit v1.2.2