[PATCH v2 2/4] powerpc/spinlock: support vcpu preempted check
xinhui at linux.vnet.ibm.com
Sat Jul 16 01:35:14 AEST 2016
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 at gmail.com>
>> Suggested-by: Peter Zijlstra (Intel) <peterz at infradead.org>
>> Signed-off-by: Pan Xinhui <xinhui.pan at 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
>> + * 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.
>> + */
>> + return !!(be32_to_cpu(lppaca_of(cpu).yield_count) & 1);
>> static __always_inline int arch_spin_value_unlocked(arch_spinlock_t lock)
>> return lock.slock == 0;
> Balbir Singh.
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