Operating System #33 Threads: Thread Model, Thread vs Process, pthread library

Operating System #33 Threads: Thread Model, Thread vs Process, pthread library. Best Programming Courses @ https://goo.gl/MVVDXR
Complete Operating Systems Lecture/ Tutorials from IIT @ https://goo.gl/GMr3if
MATLAB Tutorials @ https://goo.gl/EiPgCF

12:00 Thread Model: Create 1 process with 4 threads; each loop does 1/4th of the work
1 fork system call needed;4 threads need to be created --- much more lighter.
Each thread is not isolated from others.
Management of threads with fewer or no system calls.
Shared instructions, global,thread has its own stack.

15:52 Threads:
• Separate streams of execution within a single process
• Threads in a process not isolated from each other
• Each thread state (thread control block) contains
– Registers (including EIP, ESP)
– stack

22:27 Threads vs Processes:
• A thread has no data segment or heap whereas a process has code, heap,stack, other segments.
• A thread cannot live on its own. It needs to be attached to a process. Whereas A process has at-least one thread.
• There can be more than one thread in a process.Each thread has its own stack. Whereas Threads within a process share the same code, files.
• If a thread dies, its stack is reclaimed whereas If a process dies, all threads die.

25:14 pthread library:

Create a thread in a process
int pthread_create(pthread_t *thread,
const pthread_attr_t *attr,
void *(*start_routine) (void *),
void *arg);

Destroying a thread
void pthread_exit(void *retval);

• Join : Wait for a specific thread to complete
int pthread_join(pthread_t thread, void **retval);

28:48 Thread Example