Reading Code

Reading Code

[Nick Krause]

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

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
>

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
>

Reading Code

[Nick Krause]

On Fri, Aug 8, 2014 at 3:40 PM, Pol <poleyschen@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