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User-Agent: Mozilla/4.72 [en] (X11; U; Linux 2.2.14-5.0 i686)


I wrote a new device driver as a module.
When I'm writing too many messages with printk() without giving up CPU,
klogd buffer gets overflowed and syslog starts getting part of the message,
which is written to /var/log/messages (syslog.conf is *.info
/var/log/messages).
 


Reproducible: Sometimes
Steps to Reproduce:
1.try to make printk more than 1000 time
2.type dmesg to see all the debug messages
3.type tail -f /var/log/messages to see the trunck strings of your messages

Use strace command on klogs and syslog processes to see the communication
	

Actual Results:  we get some part of debug messages in /var/log/messages

Expected Results:  The configuration for syslog is *.info /var/log/messages
so we don't have debug messages or part of debug messages in
/var/log/messages

Code of device driver:

static int short_driver_ioctl(struct inode* inode, struct file* file,
unsigned int cmd, unsigned long arg)
{
	int rc,cpt,i;
	cpt=(int) arg;
              rc=1;
	for(i=0;i<cpt;i++)
	{
		printk(KERN_DEBUG "%d: This is a long message :
********************************************************\n",i);
		/*current->state = TASK_INTERRUPTIBLE;
		schedule_timeout(1);*/
	}
	return rc;
}


Application code
#include <sys/ioctl.h>
#include <stdio.h>
#include <fcntl.h>
#include "short_driver.h"
#include <syslog.h>




int main()
{
  int m_fd;
  int value;
  int i;
  printf("Begin of driver Test \n");
  printf("Give the number of iterations you want:");
  scanf("%d",&value);
  m_fd = open("/dev/shortdriver", O_RDWR);
  ioctl(m_fd,SHORTDRIVER_TEST_CMD,value);
  printf("End of driver Test\n");
  return(0);
}


When we give up the CPU for a time, we haven't any more the problem.
In fact the problem is that klogd make to try to read all the messages in
loop in only one time, and its buffer (4096) gets overflows. (See with
strace -p pid_klogd)


Thank for help.