Messages in this thread | | | Subject | Re: [PATCH v2 2/4] powerpc/spinlock: support vcpu preempted check | From | Pan Xinhui <> | Date | Fri, 15 Jul 2016 23:35:14 +0800 |
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Hi, Baibir sorry for late responce, I missed reading your mail.
在 16/7/6 18:54, Balbir Singh 写道: > On Tue, 2016-06-28 at 10:43 -0400, Pan Xinhui wrote: >> This is to fix some lock holder preemption issues. Some other locks >> implementation do a spin loop before acquiring the lock itself. Currently >> kernel has an interface of bool vcpu_is_preempted(int cpu). It take the cpu > ^^ takes >> as parameter and return true if the cpu is preempted. Then kernel can break >> the spin loops upon on the retval of vcpu_is_preempted. >> >> As kernel has used this interface, So lets support it. >> >> Only pSeries need supoort it. And the fact is powerNV are built into same > ^^ support >> kernel image with pSeries. So we need return false if we are runnig as >> powerNV. The another fact is that lppaca->yiled_count keeps zero on > ^^ yield >> powerNV. So we can just skip the machine type. >>
Blame on me, I indeed need avoid such typo.. thanks for pointing it out.
>> Suggested-by: Boqun Feng <boqun.feng@gmail.com> >> Suggested-by: Peter Zijlstra (Intel) <peterz@infradead.org> >> Signed-off-by: Pan Xinhui <xinhui.pan@linux.vnet.ibm.com> >> --- >> arch/powerpc/include/asm/spinlock.h | 18 ++++++++++++++++++ >> 1 file changed, 18 insertions(+) >> >> diff --git a/arch/powerpc/include/asm/spinlock.h b/arch/powerpc/include/asm/spinlock.h >> index 523673d..3ac9fcb 100644 >> --- a/arch/powerpc/include/asm/spinlock.h >> +++ b/arch/powerpc/include/asm/spinlock.h >> @@ -52,6 +52,24 @@ >> #define SYNC_IO >> #endif >> >> +/* >> + * This support kernel to check if one cpu is preempted or not. >> + * Then we can fix some lock holder preemption issue. >> + */ >> +#ifdef CONFIG_PPC_PSERIES >> +#define vcpu_is_preempted vcpu_is_preempted >> +static inline bool vcpu_is_preempted(int cpu) >> +{ >> + /* >> + * pSeries and powerNV can be built into same kernel image. In >> + * principle we need return false directly if we are running as >> + * powerNV. However the yield_count is always zero on powerNV, So >> + * skip such machine type check > > Or you could use the ppc_md interface callbacks if required, but your > solution works as well >
thanks, So I can keep my code as is.
thanks xinhui
>> + */ >> + return !!(be32_to_cpu(lppaca_of(cpu).yield_count) & 1); >> +} >> +#endif >> + >> static __always_inline int arch_spin_value_unlocked(arch_spinlock_t lock) >> { >> return lock.slock == 0; > > > Balbir Singh. >
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