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authorLinus Torvalds <torvalds@linux-foundation.org>2009-06-10 16:15:59 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2009-06-10 16:15:59 -0700
commit595dc54a1da91408a52c4b962f3deeb1109aaca0 (patch)
tree918dd8ad8bfb44410b16fea7901c3a81111fa831 /arch/x86/kernel/tsc.c
parent9b29e8228a5c2a169436a1a90a60b1f88cb35cd1 (diff)
parent7d96fd41cadc55f4e00231c8c71b8e25c779f122 (diff)
Merge branch 'x86-vdso-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip
* 'x86-vdso-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip: x86: move rdtsc_barrier() into the TSC vread method
Diffstat (limited to 'arch/x86/kernel/tsc.c')
-rw-r--r--arch/x86/kernel/tsc.c11
1 files changed, 10 insertions, 1 deletions
diff --git a/arch/x86/kernel/tsc.c b/arch/x86/kernel/tsc.c
index 84d27356c3d..3e1c057e98f 100644
--- a/arch/x86/kernel/tsc.c
+++ b/arch/x86/kernel/tsc.c
@@ -710,7 +710,16 @@ static cycle_t read_tsc(struct clocksource *cs)
#ifdef CONFIG_X86_64
static cycle_t __vsyscall_fn vread_tsc(void)
{
- cycle_t ret = (cycle_t)vget_cycles();
+ cycle_t ret;
+
+ /*
+ * 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();
+ ret = (cycle_t)vget_cycles();
+ rdtsc_barrier();
return ret >= __vsyscall_gtod_data.clock.cycle_last ?
ret : __vsyscall_gtod_data.clock.cycle_last;