diff options
author | Andy Lutomirski <luto@kernel.org> | 2015-06-25 18:44:08 +0200 |
---|---|---|
committer | Ingo Molnar <mingo@kernel.org> | 2015-07-06 15:23:29 +0200 |
commit | 03b9730b769fc4d87e40f6104f4c5b2e43889f19 (patch) | |
tree | a3f46bac8fc6ee76933f5f17c2d9f30059957529 /arch/x86/entry/vdso | |
parent | 4ea1636b04dbd66536fa387bae2eea463efc705b (diff) | |
download | linux-03b9730b769fc4d87e40f6104f4c5b2e43889f19.tar.bz2 |
x86/asm/tsc: Add rdtsc_ordered() and use it in trivial call sites
rdtsc_barrier(); rdtsc() is an unnecessary mouthful and requires
more thought than should be necessary. Add an rdtsc_ordered()
helper and replace the trivial call sites with it.
This should not change generated code. The duplication of the
fence asm is temporary.
Signed-off-by: Andy Lutomirski <luto@kernel.org>
Signed-off-by: Borislav Petkov <bp@suse.de>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Huang Rui <ray.huang@amd.com>
Cc: John Stultz <john.stultz@linaro.org>
Cc: Len Brown <lenb@kernel.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: kvm ML <kvm@vger.kernel.org>
Link: http://lkml.kernel.org/r/dddbf98a2af53312e9aa73a5a2b1622fe5d6f52b.1434501121.git.luto@kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Diffstat (limited to 'arch/x86/entry/vdso')
-rw-r--r-- | arch/x86/entry/vdso/vclock_gettime.c | 16 |
1 files changed, 2 insertions, 14 deletions
diff --git a/arch/x86/entry/vdso/vclock_gettime.c b/arch/x86/entry/vdso/vclock_gettime.c index 0340d93c18ca..ca94fa649251 100644 --- a/arch/x86/entry/vdso/vclock_gettime.c +++ b/arch/x86/entry/vdso/vclock_gettime.c @@ -175,20 +175,8 @@ static notrace cycle_t vread_pvclock(int *mode) notrace static cycle_t vread_tsc(void) { - cycle_t ret; - u64 last; - - /* - * Empirically, a fence (of type that depends on the CPU) - * before rdtsc is enough to ensure that rdtsc is ordered - * with respect to loads. The various CPU manuals are unclear - * as to whether rdtsc can be reordered with later loads, - * but no one has ever seen it happen. - */ - rdtsc_barrier(); - ret = (cycle_t)rdtsc(); - - last = gtod->cycle_last; + cycle_t ret = (cycle_t)rdtsc_ordered(); + u64 last = gtod->cycle_last; if (likely(ret >= last)) return ret; |