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Old 03-13-2013, 05:43 AM   #1
veena hosur
LQ Newbie
Registered: Feb 2013
Posts: 13

Rep: Reputation: Disabled
dereferencing pointer to an incomplete type

#include <linux/fs.h>
#include <linux/init.h>
#include <linux/pid_namespace.h>
#include <linux/proc_fs.h>
#include <linux/sched.h>
#include <linux/seq_file.h>
#include <linux/seqlock.h>
#include <linux/timer.h>

#include <linux/module.h>
#include <linux/slab.h>
#include <linux/errno.h>
#include <linux/kernel_stat.h>
#include <linux/netdevice.h>


#define FSHIFT          11              /* nr of bits of precision */
#define FIXED_1         (1<<FSHIFT)     /* 1.0 as fixed-point */
#define LOAD_INT(x) ((x) >> FSHIFT)
#define LOAD_FRAC(x) LOAD_INT(((x) & (FIXED_1-1)) * 100)

#define per_cpu(var, cpu) \
                  (*SHIFT_PERCPU_PTR(&(var), per_cpu_offset(cpu)))

DECLARE_PER_CPU(struct rq, runqueues);

#define cpu_rq(cpu)  (&per_cpu(runqueues, (cpu)))

extern int nr_threads;
extern unsigned long avnrun[]; /* Load averages */
/* get_avenrun - get the load average array
 @loads: pointer to dest load array
 @offset: offset to add
 @shift: shift count to shift the result left
extern void get_avenrun(unsigned long *loads, unsigned long offset, int shift)
   loads[0] = (avenrun[0] + offset) << shift;
   loads[1] = (avenrun[1] + offset) << shift;
   loads[2] = (avenrun[2] + offset) << shift;

  externally visible scheduler statistics: current number of runnable
  threads performed since bootup
extern unsigned long nr_running(void)
         unsigned long i, sum = 0;
                 sum += cpu_rq(i)->nr_running;
         return sum;

/*calcualation of cpu load*/
static int loadavg_proc_show(struct seq_file *m, void *v)
  //unsigned long avnrun[3];
  get_avenrun(avnrun, FIXED_1/200, 0);
  seq_printf(m, "%lu.%02lu %lu.%02lu %lu.%02lu /%d %d\n",
              LOAD_INT(avnrun[0]), LOAD_FRAC(avnrun[0]),
              LOAD_INT(avnrun[1]), LOAD_FRAC(avnrun[1]),
              LOAD_INT(avnrun[2]), LOAD_FRAC(avnrun[2]),
  return 0;

/* single_open open the virtual file.when output time comes it will call
   loadavg_proc_show function*/

static int loadavg_proc_open(struct inode *inode, struct file *file)
    return single_open(file, loadavg_proc_show, NULL);

/*The operations  - read(), llseek(), and release() - are
   all implemented by the seq_file code itself. So a virtual file's
   file_operations structure */
static const struct file_operations loadavg_proc_fops = {
                 .open	= loadavg_proc_open,
                 .read	= seq_read,
                 .llseek = seq_lseek,
                 .release = single_release,

/*loading the module*/
static int __init proc_loadavg_init(void)
   proc_create("loadavg", 0, NULL, &loadavg_proc_fops);
   return 0;

/*unloading the module*/
static void __exit proc_loadavg_exit(void)
     remove_proc_entry("loadavg", NULL);

this is the perfect way of calculating cpuload in kernel mode.if yes i am getting dereferencing pointer to incomplete type error in sum += cpu_rq(i)->nr_running line please tell me the solution.if not tell me how to calculate
Old 03-13-2013, 05:45 AM   #2
veena hosur
LQ Newbie
Registered: Feb 2013
Posts: 13

Original Poster
Rep: Reputation: Disabled
its very urget please reply me
Old 03-13-2013, 06:29 AM   #3
LQ Guru
Registered: Dec 2007
Distribution: Centos
Posts: 5,286

Rep: Reputation: 1190Reputation: 1190Reputation: 1190Reputation: 1190Reputation: 1190Reputation: 1190Reputation: 1190Reputation: 1190Reputation: 1190
That error message means you needed to include the .h file that defines the struct whose member you are accessing.

Between the macros and the incomplete code, I can't guess what struct that is, so I can't guess what .h file it is.
Maybe you know what struct you are accessing or maybe the error message tells you more than you quoted.

Originally Posted by veena hosur View Post
its very urget please reply me
Some experts here will resent a post like that enough that they will skip replying, even if they know the answer.

In my opinion, if the question was urgent FOR YOU, then YOU should have put a bit more effort into providing enough information to enable a better answer on the first try (rather than have me say I can't guess which struct you need the definition of included).

Last edited by johnsfine; 03-13-2013 at 06:32 AM.


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