Messages in this thread | | | Date | Sat, 13 Jun 2015 11:02:11 +0200 | From | Borislav Petkov <> | Subject | Re: [PATCH v2 15/17] x86: Add rdtsc_ordered() and use it in trivial call sites |
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On Fri, Jun 12, 2015 at 04:44:55PM -0700, Andy Lutomirski wrote: > barrier_before_rdtsc(); rdtsc_unordered() 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. > > Signed-off-by: Andy Lutomirski <luto@kernel.org> > ---
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> diff --git a/arch/x86/include/asm/msr.h b/arch/x86/include/asm/msr.h > index a47fb11af5f5..22d69d2d1f0d 100644 > --- a/arch/x86/include/asm/msr.h > +++ b/arch/x86/include/asm/msr.h > @@ -148,6 +148,20 @@ static __always_inline void barrier_before_rdtsc(void) > "lfence", X86_FEATURE_LFENCE_RDTSC); > } > > +/** > + * rdtsc_ordered() - read the current TSC in program order > + * > + * rdtsc_ordered() returns the result of RDTSC as a 64-bit integer. > + * It is ordered like a load to a global in-memory counter. It should > + * be impossible to observe non-monotonic rdtsc_unordered() behavior > + * across multiple CPUs as long as the TSC is synced. > + */ > +static __always_inline unsigned long long rdtsc_ordered(void) > +{ > + barrier_before_rdtsc(); > + return rdtsc_unordered(); > +} > +
I don't see the final tree state with all those applied (too lazy to apply them) but why not simply kill barrier_before_rdtsc() and inline the alternative into rdtsc_ordered()?
I mean, I don't see usage for it somewhere else...
-- Regards/Gruss, Boris.
ECO tip #101: Trim your mails when you reply. --
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