On 17.08.2014 19:25, Oleg Nesterov wrote:
> On 08/13, Oleg Nesterov wrote:
>>
>> Peter, could you take these simple patches ?
>>
>> Better later than never... per-file, but please feel free to join
>> them in a single patch.
>>
>> read_lock_irq*(tasklist_lock) in kernel/sched/ files looks strange.
>> Why? I'll recheck, but this looks unneeded.
>
> Yes, please consider these minor cleanups on top of for_each_thread
> conversions.
>
> read_lock_irq(tasklist) in normalize_rt_tasks() doesn't really hurt,
> but it looks confusing. If we really have a reason to disable irqs
> this (subtle) reason should be documented.
>
> And I can't understand tg_has_rt_tasks(). Don't we need something
> like the patch below? If not, please do not ask me why I think so,
> I don't understand this black magic ;) But the usage of the global
> "runqueues" array looks suspicious.
This function searches RT task which is related to this tg. It's
opaquely because it looks that there is an error.
task_rq(p)->rt.tg is a task group of a top rt_rq, while the task may
be queued on a child rt_rq instead of this. So, your patch is a BUGFIX,
not a cleanup.
> --- x/kernel/sched/core.c
> +++ x/kernel/sched/core.c
> @@ -7354,7 +7354,7 @@ static inline int tg_has_rt_tasks(struct
> struct task_struct *g, *p;
>
> for_each_process_thread(g, p) {
> - if (rt_task(p) && task_rq(p)->rt.tg == tg)
> + if (rt_task(p) && task_group(p) == tg)
> return 1;
> }
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