Reading Code

[Nick Krause]

On Fri, Aug 8, 2014 at 3:40 PM, Pol <poleyschen at hotmail.com> wrote:
> Well, seems like you have to also learn to google, since I found the answer
> to all your questions within seconds.
>
> Pol
>
>
>
> On 08.8.14 21:16, Nick Krause wrote:
>>
>> For the last few days , I have been reading the code for do_fork and
>> other parts of the scheduler code.
>> As most of the developers feel this is in my best interest. I do
>> however have a few questions about the
>> code for the function, schedule.
>> 1. In task struct we have this one defined if needed
>> 1481 #ifdef CONFIG_BLOCK
>> 1482 /* stack plugging */
>> 1483 struct blk_plug *plug;
>> 1484 #endif
>> I am curious is this used for block IO or something else as we are
>> checking for it in schedule() with this line,
>> sched_submit_work(tsk); which in turn points to sched_submit_work and
>> in turn checks for blk_plug
>> 2814 static inline void sched_submit_work(struct task_struct *tsk)
>> 2815 {
>> 2816 if (!tsk->state || tsk_is_pi_blocked(tsk))
>> 2817 return;
>> 2818 /*
>> 2819 * If we are going to sleep and we have plugged IO queued,
>> 2820 * make sure to submit it to avoid deadlocks.
>> 2821 */
>> 2822 if (blk_needs_flush_plug(tsk))
>> 2823 blk_schedule_flush_plug(tsk);
>> 2824 }
>> Since schedule returns this and after searching using lxr, can't find
>> much on this, what is this type actually defined as when compiled?
>> 368 #define __sched __attribute__((__section__(".sched.text")))
>> 3. context_switch(rq, prev, next); /* unlocks the rq */
>> I am getting confused by this function after tracing it, if  someone
>> wants to explain it to me that would be great.
>>
>> In addition I am not not trying to turn this into a self help just for
>> me, but my questions about git I goggled for 2 hours and didn't
>>
>> find any answers, sorry about that guys. In addition I hope theses
>> questions are valid.
>> Cheers Nick
>>
>
Pol,
I think perhaps I was goggling the wrong things. If someone wants to
help me answer my questions that would be great.
Sorry Pol