Hi Xinhui, On Mon, Jun 27, 2016 at 01:41:29PM -0400, Pan Xinhui wrote: > This is to fix some holder preemption issues. Spinning at one > vcpu which is preempted is meaningless. > > Kernel need such interfaces, So lets support it. > > We also should suooprt both the shared and dedicated mode. > So add lppaca_dedicated_proc macro in lppaca.h > > Suggested-by: Boqun Feng <boqun.f...@gmail.com> > Signed-off-by: Pan Xinhui <xinhui....@linux.vnet.ibm.com> > --- > arch/powerpc/include/asm/lppaca.h | 6 ++++++ > arch/powerpc/include/asm/spinlock.h | 15 +++++++++++++++ > 2 files changed, 21 insertions(+) > > diff --git a/arch/powerpc/include/asm/lppaca.h > b/arch/powerpc/include/asm/lppaca.h > index d0a2a2f..0a263d3 100644 > --- a/arch/powerpc/include/asm/lppaca.h > +++ b/arch/powerpc/include/asm/lppaca.h > @@ -111,12 +111,18 @@ extern struct lppaca lppaca[]; > * we will have to transition to something better. > */ > #define LPPACA_OLD_SHARED_PROC 2 > +#define LPPACA_OLD_DEDICATED_PROC (1 << 6) >
I think you should describe a little bit about the magic number here,
i.e. what document/specification says this should work, and how this
works.
> static inline bool lppaca_shared_proc(struct lppaca *l)
> {
> return !!(l->__old_status & LPPACA_OLD_SHARED_PROC);
> }
>
> +static inline bool lppaca_dedicated_proc(struct lppaca *l)
> +{
> + return !!(l->__old_status & LPPACA_OLD_DEDICATED_PROC);
> +}
> +
> /*
> * SLB shadow buffer structure as defined in the PAPR. The save_area
> * contains adjacent ESID and VSID pairs for each shadowed SLB. The
> diff --git a/arch/powerpc/include/asm/spinlock.h
> b/arch/powerpc/include/asm/spinlock.h
> index 523673d..ae938ee 100644
> --- a/arch/powerpc/include/asm/spinlock.h
> +++ b/arch/powerpc/include/asm/spinlock.h
> @@ -52,6 +52,21 @@
> #define SYNC_IO
> #endif
>
> +/* For fixing some spinning issues in a guest.
> + * kernel would check if vcpu is preempted during a spin loop.
> + * we support that.
> + */
> +#define arch_vcpu_is_preempted arch_vcpu_is_preempted
> +static inline bool arch_vcpu_is_preempted(int cpu)
This function should be guarded by #ifdef PPC_PSERIES .. #endif, right?
Because if the kernel is not compiled with guest support,
vcpu_is_preempted() should always be false, right?
> +{
> + struct lppaca *lp = &lppaca_of(cpu);
> +
> + if (unlikely(!(lppaca_shared_proc(lp) ||
> + lppaca_dedicated_proc(lp))))
Do you want to detect whether we are running in a guest(ie. pseries
kernel) here? Then I wonder whether "machine_is(pseries)" works here.
Regards,
Boqun
> + return false;
> + return !!(be32_to_cpu(lp->yield_count) & 1);
> +}
> +
> static __always_inline int arch_spin_value_unlocked(arch_spinlock_t lock)
> {
> return lock.slock == 0;
> --
> 2.4.11
>
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