Questions about struct task_struct

[Nick Krause]

On Wed, Aug 6, 2014 at 6:23 PM, Venkatram Tummala
<venkatram867 at gmail.com> wrote:
> On 08/06/2014 03:11 PM, Nick Krause wrote:
>> I am new to kernel programming and have a lot  questions about this
>> structure. Also if after you guys reply I have a few \
>> questions for Greg Kroah Hartman about usb development and stable
>> trees. I am very excited about learning this properly
>> now and if anyone notices something wrong in my understanding please
>> let me known :).
>> Thanks So Much,
>> Nick
>> Questions about task_struct
>> 1.volatile long state; Is this line like jiffies for timers with
>> regards to the keyword volatile?
>> 2.void *stack; Is this a pointer to the kernel stack for the process
>> related to the process
>> that the structure is keeping data for and is void to make it an
>> opaque data type? Is this
>> normally an int or some other data type when called with most processes?
>> 3.unsigned int flags; /* per process flags, defined below */, My only
>> question about this is
>> what flags are there and are these the ifdef statements in the struct?
>> 4.Why are we making the usage count atomic?(pretty obvious but real
>> world reasons would be great)
>> 5.I assume int ptrace is for ptrace or debugged processes? If I wrong
>> please let me known too.
>> 6. What is wakkee_flips and wakkee_flips_decay used for?
>> 7.This is probably a stupid question but are these the scheduler cases for CFS?
>> 1240 int on_rq;
>> 1241
>> 1242 int prio, static_prio, normal_prio;
>> 1243 unsigned int rt_priority;
>> 1244 const struct sched_class *sched_class;
>> 1245 struct sched_entity se;
>> 1246 struct sched_rt_entity rt;
>> 1247 #ifdef CONFIG_CGROUP_SCHED
>> 1248 struct task_group *sched_task_group;
>> 1249 #endif
>> 1250 struct sched_dl_entity dl;
>> 8.What are preempt notifiers and what are they for?(another stupid question)
>> 9. Are these lines for the policy used and to block certain processes
>> to only a few processors?
>> 1261 unsigned int policy;
>> 1262 int nr_cpus_allowed;
>> 1263 cpumask_t cpus_allowed;
>> 8.What are the options like CONFIG_PREEMPT_RCU used for in terms of
>> workloads or locking as I heard a lot about
>> them on the threads on the lkml?
>
> Go learn C first.
>
> BTW, We all know that you were here on the mailing list before with the
> name "James Bond". Now, its Nick Krause. You have irritated many guys
> before this. Unfortunately, changing the name wont change the attitude.
>
> I am pretty sure you will come back with a different name now.
>
> Dude, seriously. Stop it.!
>
>>
>> P.S. Sorry about some many questions,. Answer then whenever you guys
>> have time and if there stupid and easily found
>> somewhere let me known.
>>
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>
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No I not coming back with another name, I would like my questions
answered first.
Nick