Linux, Programming, Bash & my thoughts…

systemtap script linux scsi timeout

January 19, 2012 at 9:44 AM (Uncategorized)

1 #!/usr/bin/stap
2
3 probe begin{
4         print(“Starting probe, watching for SG_IO with threshold greater than “);
5             print($1 / 1000);
6                 print(” seconds.\nType control-c to stop.\n”);
7 }
8
9 probe kernel.function(“sg_io”)
10 {
11         if ($hdr->timeout > $1) {
12                    printf(“%s(%d) called sg_io with timeout = %d, greater than threshold\n”,
13                                         execname(), pid(), $hdr->timeout);
14         }
15         if ($q->sg_timeout > $1){
16                     printf(“%s(%d) called sg_io with sg_timeout = %d, greater than threshold\n”,
17                     execname(), pid(), $q->sg_timeout);
18         }
19 }
20
21 probe end {
22         print(“End probe\n”);
23 }

 281static int sg_io(struct request_queue *q, struct gendisk *bd_disk,
 282                struct sg_io_hdr *hdr, fmode_t mode)
 283{
 284        unsigned long start_time;

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bit play with signed unsigned

December 8, 2011 at 9:47 AM (Uncategorized)

[root@dhcp209-92 /]# cat size_t_size.c
#include <stdio.h>
#include <stdlib.h>
int main() {
size_t len = -1;
/*    ssize_t chk = -1;
size_t toprint;
printf(“size of size_t is %d”, sizeof(size_t));
printf(“size of ssize_t is %d”, sizeof(ssize_t));
printf(“len is %d”, len);
toprint = (int) len;
printf(“toprint is %d”, toprint);
*/
if( len <= 0 || len == -1)
printf(” -1 if cond worked”);
//    if ( len == chk )
//        printf(” -1 cond worked”);
return 0;
}
[root@dhcp209-92 /]#

I don’t prefer to post output for different conditions as I want readers to try it out so that they understand it better .

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C snippet showing conditional function prototype

November 4, 2011 at 11:40 AM (Uncategorized)

1441         send_file_entry(f, fbuf, file,
1442 #ifdef SUPPORT_LINKS
1443                 symlink_name, symlink_len,
1444 #endif
1445                 flist->used, flist->ndx_start);

389 static void send_file_entry(int f, const char *fname, struct file_struct *file,
390 #ifdef SUPPORT_LINKS
391                 const char *symlink_name, int symlink_len,
392 #endif
393                 int ndx, int first_ndx)

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signals linux ipc

August 19, 2011 at 9:26 AM (Uncategorized)

0x00000fff922453cc in do_sigsuspend (set=0xfffc72dc668) at ../sysdeps/unix/sysv/linux/sigsuspend.c:63
63        return INLINE_SYSCALL (rt_sigsuspend, 2, CHECK_SIGSET (set), _NSIG / 8);

If pattern

<signal handler called>

is not present around above bt snippet then signal didn't occur and process which have
called sigsuspend has terminated abnormally.

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How to use syslog for logging messages

August 8, 2011 at 12:18 PM (Uncategorized)

[root@mdarade sample_code]# cat syslog_md.c
#include <stdio.h>
#include <syslog.h>
#include <unistd.h>
int main() {
char hello[]=”mahaveer darade”;
openlog(“syslog_md”, LOG_PID, LOG_DAEMON );
syslog(LOG_INFO, “%s\n”, hello);
printf(“pid is %d\n”, getpid());
closelog();
return 0;
}
[root@mdarade sample_code]#

[root@mdarade sample_code]# tail -f /var/log/messages
Aug  8 17:43:14 mdarade syslog_md[4144]: mahaveer darade

Config files: /etc/syslog.conf, /etc/sysonfig/syslog

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script to find files having ge number of lines

August 4, 2011 at 12:17 PM (Uncategorized)

[mdarade@mdarade net-snmp-5.3.2.2]$ cat ~/scripts/find_files_having_specific_number_of_lines.sh
#!/usr/bin/env bash
find . -type f | while read line
do
        no_of_lines=`wc -l $line| cut -d" " -f1`;
        if [ $no_of_lines -ge $1 ] ; then
            ls -l "$line";
        fi
done
[mdarade@mdarade net-snmp-5.3.2.2]$ 

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