linux module location

/lib/modules/2.6.18-92.el5/kernel/drivers

HZ & jiffies

HZ是用來定義每一秒有幾次timer interrupts(time tick)

jiffies:

the number of time ticks since kernel start

ex:

unsigned long timeout=jiffies+ 3*HZ;

//  the time after 3 second

time_after(jiffies, timeout)

convert from jiffies to seconds

divide by HZ

time related methods:

time_after:  parameter is time tick 

time_before: parameter is time tick

schedule_timeout: parameter is time tick  

only schedule_timeout will give up processor

wait_event_timeout:

msleep: parameter is milliseconds

timer example( do something in the future):

#include

struct timer_list my_timer;

init_timer(&my_timer);            /* Also see setup_timer() */

my_timer.expire = jiffies + n*HZ; /* n is the timeout in number

                                     of seconds */

my_timer.function = timer_func;   /* Function to execute

                                     after n seconds */

my_timer.data = func_parameter;   /* Parameter to be passed

                                     to timer_func */

add_timer(&my_timer);             /* Start the timer */

smp

smp(多cpu)

rpm

remove rpm:

rpm -e test

query info about specific rpm

ex: 

rpm -q  test

rpm for red hat and cent os

Because red hat & cent os are related , we can get rpm for ret hat from rpm for cent os 

init network

開機網路設定:

/etc/sysconfig/network/

ifcfg-lo

ifcfg-eth0

blk_queue_make_request

 void blk_queue_make_request (request_queue_t * q, make_request_fn * mfn);

define an alternate make_request function for a device

ARGUMENTS

q

the request queue for the device to be affected

mfn

the alternate make_request function