On Thu, Jun 09, 2016 at 01:23:23PM +0200, Paolo Bonzini wrote:
> The version field in struct pvclock_vcpu_time_info basically implements
> a seqcount. Wrap it with the usual read_begin and read_retry functions,
> and use these APIs instead of peppering the code with smp_rmb()s.
> While at it, change it to the more pedantically correct virt_rmb().
>
> With this change, __pvclock_read_cycles can be simplified noticeably.
>
> Signed-off-by: Paolo Bonzini <pbonzini@xxxxxxxxxx>
> ---
> arch/x86/entry/vdso/vclock_gettime.c | 25 +++++------------------
> arch/x86/include/asm/pvclock.h | 39 +++++++++++++++++++++---------------
> arch/x86/kernel/pvclock.c | 17 ++++++----------
> 3 files changed, 34 insertions(+), 47 deletions(-)
[...]
> --- a/arch/x86/include/asm/pvclock.h
> +++ b/arch/x86/include/asm/pvclock.h
[...]
> @@ -69,23 +87,12 @@ static inline u64 pvclock_scale_delta(u64 delta, u32 mul_frac, int shift)
> }
>
> static __always_inline
> -unsigned __pvclock_read_cycles(const struct pvclock_vcpu_time_info *src,
> - cycle_t *cycles, u8 *flags)
> +cycle_t __pvclock_read_cycles(const struct pvclock_vcpu_time_info *src)
> {
> - unsigned version;
> - cycle_t offset;
> - u64 delta;
> -
> - version = src->version;
> - /* Make the latest version visible */
> - smp_rmb();
This is on top of Minfei's patch, right? It isn't in Linus' tree yet so
I wonder if it makes sense to merge the two patches into one.
Will you post it to stable, too?
Anyway
Reviewed-by: Roman Kagan <rkagan@xxxxxxxxxxxxx>
Roman.
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