[Linux]A glance at data types used by kernel data

Data types used by kernel data divided into three main classes . Those are standard C types. eg:- int explicitly sized types . eg:- u32 Interface specific types => types used for specific kernel objects . eg:- pid_t  

[Linux][C]How to specify a process as the owner of the file ?

When a process invokes F_SETOWN command using fnctl system call, the process ID of the owner process is saved in filp->f_owner which can be used to address the file . Usage eg:-      fd = open(“/dev/filename”, O_RDONLY);         if (fd < 0) {                fprintf(stderr, ” failed to open /dev/filename \n”);                return;        }         if ((fcntl(fd,

[Linux]What is Thundering herd problem in Linux point of view ?

We studied about the forms of wait_event and wake_up macros in Linux device driver text book. These macros are used to sleep the process while waiting for an event and  wake up from the sleep state when even occurs . So when a process calls wake_up on a wait queue, all processes waiting on that

[Linux][C]Which are all the file operations affected by the nonblocking flag (O_NONBLOCK) ?

The file operations affected by the non blocking flag are open read write    

[Linux]A little about Timer Wheel

The original kernel timer system is known as Timer wheel. It is based on incrementing kernel- internal value (jiffie) on every timer interrupt. This timer interrupt becomes the default scheduling quantum. All the other timers are based on jiffies.

[Linux driver]A Little about put_user & __put_user

  put_user and __put_user used to write the datum to user space Function Declaration of put_user => put_user(datum, ptr)           Function Declaration of __put_user => __put_user(datum, ptr) When single values are to be transferred, put_user/ __put_user should be called instead copy_to_user . Reason behind this is        these functions(put_user/__put_user ) are relatively fast.   Difference

[Linux][C]What is the reason for returning -ENOTTY for incorrect ioctl command ?

There is a system call fcntl which is very similar to the system call ioctl.But it is kept separate from ioctl for following reasons: when Unix developers faced the problem of controlling I/O operations , they decided that files and devices were different. At the time, the only devices with ioctl implementations were ttys  

[Linux][C]What should the default section be when the command number in driver ioctl function doesn’t match a valid operation ?

According to POSIX standard, if an inappropriate ioctl command has been issued , then -ENOTTY should be returned. The error code for -ENOTTY is ” inappropriate ioctl for device” But it is common that the error code for -EINVAL returns on the default section of ioctl switch statement, which says “invalid ioctl command” .  

[Linux]Significance of rc.local

This script will be executed *after* all the other init scripts. We can put  the customized script  here, which needed to be run after system up. Also depending upon run level , there will be a local file. Like if System’s runlevel is 5 /etc/rc5.d/S99local is the file . There you can put the script which

[Windows]How to open the task manager on a windows remote desktop session

There are many ways to open task manager on a Windows remote desktop session 1) Press Ctrl-Shift-ESC 2) Right-click the taskbar and click Task Manager. 3) click Start → Run, then type taskmgr.