Reading Code

[Pol Eyschen]

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
>