Re: task_struct and uid of a task

[sena <auntvini@sedal.usyd.edu.au>]

Robin,

Thanks for your willingness to assist me. Then I will ask questions from 
you too.

I have already compiled the new kernel and it is up and running.

In my next kernel update I will follow your avice to naming and indentation.

One of my friends from India told me to direct this question to Rusty 
Russel as they are very impressed about his guidance.

Thus I will keep him as my main Guru.


What I intend to do is: This is to prove a point in a Research Paper.

I am going to count number of queued and runnable processes which 
belongs to each user login(uid). Then I would apply loadavg calculations 
seperately.

The problem is in task_struct. The uids in task_struct is parents uid 
(as some childs inherits it)

So if I go by that uid while counting the processes, then I would make a 
mistake.

At this stage in my newly compiled kernel, I find that mistake staight away.


Wishing you a Happy new Year

Sena Seneviratne
Computer Engineering Lab
Sydney University
Sydney


Robin Holt wrote:

>On Wed, Dec 31, 2003 at 07:06:52AM +1100, sena wrote:
>
>Sena,
>
>Why don't you pester me about this instead of bothering Rusty.
>
>What are you trying to accomplish?  Please be specific about what
>you are trying to find out and not how you are trying to do it.
>
>Another thing, I would _GREATLY_ appreciate code which has
>decent variable names and good indentation.  Assuming you are
>writing this on a Linux box with a standard development install,
>you should be able to do:
>
>indent -kr -i8 -psl -npcs -cp9 myfile.c
>
>and get very kernel-style code.  Won't fix the variable names, but
>at least braces will be indented.
>
>Thanks,
>Robin Holt
>
>  
>
>>Dear Rusty,
>>
>>Thank you for your previous reply. I feel like you would be able to 
>>assist me.
>>
>>Say a computer has 5 user logins name1(500), name2(501), 
>>name3(502).........name5(504) apart from root. If these 5 people 
>>remotely login and runs there jobs, then the user name of those jobs are 
>>name1,name2 and name3.
>>
>>Say if they use telnet to remotely login then those Tasks will be 
>>started under telnet server as children.
>>
>>As the children inherits uid, euid etc of the parents. That means telnet 
>>is run as root and it inherits uid<500.
>>
>>task_struct has uid and it is updated accordingly.
>>
>>
>>I have built the kernel 2.4.19sena1 successfully but this is my problem. 
>>The problem because child process inherits uid etc if I start any 
>>process through telnet
>>
>>My code is as follows:
>>
>>unsigned long a; //for root uid<500, I am getting this uidArray[0] is 
>>for storing uid (assumed 100 for all <500)
>>unsigned long b; //for 500
>>unsigned long c; //for 501
>>unsigned long d; //for 502
>>unsigned long e; //for 503
>>unsigned long f; // for 504
>>
>>unsigned int uidArray[7];
>>
>>static unsigned long count_active_tasks(void)
>>{
>>   struct task_struct *p;
>>   unsigned long nr = 0;
>>
>>   int s = 0;
>>  
>>   int i=0;
>>   int j=0;
>>   int k=0;
>>   int m=0;
>>
>>   a=b=c=d=e=f=0;
>>  
>>      read_lock(&tasklist_lock);
>>
>>   for_each_task(p)
>>   {
>>       if ((p->state == TASK_RUNNING ||
>>            (p->state & TASK_UNINTERRUPTIBLE)))
>>   {
>>
>>       nr += FIXED_1; //nr total tasks
>>      
>>       if(i==0)
>>       {
>>           uidArray[0] = 100;
>>
>>           if(p->uid < 500)
>>           {
>>          
>>           a += FIXED_1;
>>           }
>>           else
>>           {
>>           uidArray[1] = p->uid;
>>           b += FIXED_1;
>>           k++;
>>           }
>>        k++;
>>       }
>>       else
>>       {
>>          for(j=0; j < k ; j++)
>>          {
>>              
>>           if((j==0)&& (p->uid < 500) && (s==0))
>>           {
>>               a += FIXED_1;
>>               s = 1;
>>               break;
>>           }
>>           else if((uidArray[j] == p->uid) && s==0)
>>           {
>>               if(j==1){
>>               b += FIXED_1;}
>>               if(j==2){
>>               c += FIXED_1;}
>>               if(j==3){
>>               d += FIXED_1;}
>>               if(j==4){
>>               e += FIXED_1;}
>>               if(j==5){
>>               f += FIXED_1;}
>>               s=1;
>>               break;
>>           }
>>           }
>>  
>>           if(s==0)
>>           {
>>
>>           if(k < 6)
>>              {
>>               k++;
>>               j = k-1;
>>               uidArray[j] = p->uid;
>>               if(j==1){
>>               b += FIXED_1;}
>>               if(j==2){
>>               c += FIXED_1;}
>>               if(j==3){
>>               d += FIXED_1;}
>>               if(j==4){
>>               e += FIXED_1;}
>>               if(j==5){
>>               f += FIXED_1;}
>>              }
>>              
>>
>>           }
>>
>>       s=0;
>>         }
>>      
>>       i++;
>>  
>>   }
>>
>>   }
>>          
>>   read_unlock(&tasklist_lock);
>>   return nr;
>>
>>}
>>
>>unsigned long avenrun[6];
>>
>>unsigned long avenrunT;
>>
>>static inline void calc_load(unsigned long ticks)
>>{
>>   unsigned long active_tasks;  /*fixed-point */
>>   static int count = LOAD_FREQ;
>>
>>   count -= ticks;
>>   if (count < 0) {
>>       count += LOAD_FREQ;
>>       active_tasks = count_active_tasks();
>>
>>       CALC_LOAD(avenrunT, EXP_5, active_tasks);
>>       CALC_LOAD(avenrun[0], EXP_5, a);
>>       CALC_LOAD(avenrun[1], EXP_5, b);
>>       CALC_LOAD(avenrun[2], EXP_5, c);
>>       CALC_LOAD(avenrun[3], EXP_5, d);
>>       CALC_LOAD(avenrun[4], EXP_5, e);
>>       CALC_LOAD(avenrun[5], EXP_5, f);
>>      
>>   }
>>}
>>
>>I have updated all the other places(all .h and .c files) to suit this code.
>>
>>And the result is stored in    proc/loadavg as
>>
>>       0.21   0.21   100   0.00     0       0.00      0        0.00     
>>0        0.00     0            0.00        0
>>         T        a 1      uid     b1    500        c 1     501      d1 
>>    502      e1      503          f1         504
>>
>>T- for totall
>>a1- root or uid < 500
>>b1,c1,di etc for uid>=500
>>
>>In this perticular case I have login as root so that uid 100 is seen. 
>>There is no 500 or above. they are all 0.
>>
>>But even if I start login remotely those processors started through 
>>telnet inherits uid <500. Then they will be shown under a1
>>
>>I get uids from task_struct
>>
>>Thanks
>>Sena Seneviratne
>>Computer Engineering Lab
>>School of Electrical and Information Engineering
>>Sydney University
>>
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>>
>
>  
>