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From: Yafang Shao <laoar.shao@gmail.com>
Date: Tue, 8 Aug 2017 18:36:41 +0800
Message-ID: <CALOAHbAb9rgakOK2G4p=CD8wuU7gMM-O9zSxQQv1Em=FVugJ-g@mail.gmail.com>
Subject: Re: [PATCH v2] scheduler: enhancement to show_state_filter
To: Peter Zijlstra <peterz@infradead.org>
Cc: gregkh@linuxfoundation.org, jslaby@suse.com, mingo@redhat.com,
        linux-kernel@vger.kernel.org
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Hi Peter,

In oder to make it readable, I have comment in the patch why this
change is made,
    -               if (!state_filter || (p->state & state_filter))
    +               /* in case we want to set TASK_RUNNING specifically */
    +               if ((p->state != TASK_RUNNING ? p->state << 1 : 1)
& state_filter)
                            sched_show_task(p);

show_state_filter() is only used in SysRq,  in which we can dump all
tasks (with the key 't'), or uninterruptible tasks(with the key 'w').
I think we should also dump only running tasks (with a new key, or
something else).
But in order to introduce the new key, we should made this change first.

After this change got approved, I will try to make some changes in SysRq.

Thanks
Yafang


2017-08-08 18:24 GMT+08:00 Peter Zijlstra <peterz@infradead.org>:
> On Tue, Aug 08, 2017 at 04:50:23PM +0800, Yafang Shao wrote:
>> Hi Peter,
>>
>> The point is we call use it as bellow,
>>     show_state_filter(TASK_RUNNING);
>> because TASK_RUNNING is 0, that will dump all tasks.
>>
>> Under some circumstance, we need this to dump only tasks in TASK_RUNNING state.
>
> But the patch doesn't introduce any of that. It just makes the existing
> code unreadable.