Messages in this thread | | | Date | Tue, 28 Jun 2016 11:23:57 +0800 | From | xinhui <> | Subject | Re: [PATCH 2/3] powerpc/spinlock: support vcpu preempted check |
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On 2016年06月27日 22:17, Peter Zijlstra wrote: > On Mon, Jun 27, 2016 at 01:41:29PM -0400, Pan Xinhui wrote: >> 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. >> + */ > > If you look around in that file you'll notice that the above comment > style is inconsistent. > > Nor is the comment really clarifying things, for one you fail to mention > the problem by its known name. You also forget to explain how this > interface will help. How about something like this: > > /* > * In order to deal with a various lock holder preemption issues provide > * an interface to see if a vCPU is currently running or not. > * > * This allows us to terminate optimistic spin loops and block, > * analogous to the native optimistic spin heuristic of testing if the > * lock owner task is running or not. > */ thanks!!!
> > Also, since you now have a useful comment, which is not architecture > specific, I would place it with the common vcpu_is_preempted() > definition in sched.h. > agree with you. Will do that. I will also add Suggested-by with you. thanks
> Hmm? > >> +#define arch_vcpu_is_preempted arch_vcpu_is_preempted >> +static inline bool arch_vcpu_is_preempted(int cpu) >> +{ >> + struct lppaca *lp = &lppaca_of(cpu); >> + >> + if (unlikely(!(lppaca_shared_proc(lp) || >> + lppaca_dedicated_proc(lp)))) >> + 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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