Hi, Peter
Could you make a patch for it, please? Jason J. Herne's test showed we
addressed the bug. But the fix is not in kernel yet. Some new highly
related reports are come up again.
I don't want to argue any more, no matter how the patch will be,
I will accept. And please add the following tags in your patch:
Reported-by: Sasha Levin <sasha.le...@oracle.com>
Reported-by: Jason J. Herne <jjhe...@linux.vnet.ibm.com>
Tested-by: Jason J. Herne <jjhe...@linux.vnet.ibm.com>
Acked-by: Lai Jiangshan <la...@cn.fujitsu.com>
Thanks,
Lai
On 06/06/2014 09:36 PM, Peter Zijlstra wrote:
> On Thu, Jun 05, 2014 at 06:54:35PM +0800, Lai Jiangshan wrote:
>> diff --git a/kernel/sched/core.c b/kernel/sched/core.c
>> index 268a45e..d05a5a1 100644
>> --- a/kernel/sched/core.c
>> +++ b/kernel/sched/core.c
>> @@ -1474,20 +1474,24 @@ static int ttwu_remote(struct task_struct *p, int
>> wake_flags)
>> }
>>
>> #ifdef CONFIG_SMP
>> -static void sched_ttwu_pending(void)
>> +static void sched_ttwu_pending_locked(struct rq *rq)
>> {
>> - struct rq *rq = this_rq();
>> struct llist_node *llist = llist_del_all(&rq->wake_list);
>> struct task_struct *p;
>>
>> - raw_spin_lock(&rq->lock);
>> -
>> while (llist) {
>> p = llist_entry(llist, struct task_struct, wake_entry);
>> llist = llist_next(llist);
>> ttwu_do_activate(rq, p, 0);
>> }
>> +}
>>
>> +static void sched_ttwu_pending(void)
>> +{
>> + struct rq *rq = this_rq();
>> +
>> + raw_spin_lock(&rq->lock);
>> + sched_ttwu_pending_locked(rq);
>> raw_spin_unlock(&rq->lock);
>> }
>
> OK, so this won't apply to a recent kernel.
>
>> @@ -4530,6 +4534,11 @@ int set_cpus_allowed_ptr(struct task_struct *p, const
>> struct cpumask *new_mask)
>> goto out;
>>
>> dest_cpu = cpumask_any_and(cpu_active_mask, new_mask);
>> +
>> + /* Ensure it is on rq for migration if it is waking */
>> + if (p->state == TASK_WAKING)
>> + sched_ttwu_pending_locked(rq);
>
> So I would really rather like to avoid this if possible, its doing full
> remote queueing, exactly what we tried to avoid.
>
>> +
>> if (p->on_rq) {
>> struct migration_arg arg = { p, dest_cpu };
>> /* Need help from migration thread: drop lock and wait. */
>> @@ -4576,6 +4585,10 @@ static int __migrate_task(struct task_struct *p, int
>> src_cpu, int dest_cpu)
>> if (!cpumask_test_cpu(dest_cpu, tsk_cpus_allowed(p)))
>> goto fail;
>>
>> + /* Ensure it is on rq for migration if it is waking */
>> + if (p->state == TASK_WAKING)
>> + sched_ttwu_pending_locked(rq_src);
>> +
>> /*
>> * If we're not on a rq, the next wake-up will ensure we're
>> * placed properly.
>
> Oh man, another variant.. why did you change it again? And without
> explanation for why you changed it.
>
> I don't see a reason to call sched_ttwu_pending() with rq->lock held,
> seeing as how we append to that list without it held.
>
> I'm still thinking the previous version is good, can you explain why you
> changed it?
>
>
>
>
>
>
> .
>
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