Multithreading

Hi,

Here are few possible queries that can be discussed about multithreaded programming in linux !

1. Can a child process be called as a thread ?
2. Are there multiple ways to create a thread ?
3. Is it possible for the thread to be alive if we terminate the process ? Is it possible for a child process to be alive if we terminate the parent process ? 
4. What is the memory layout of a process ?
5. What is the difference between multithreading and multiprocessing ?
6. What is the memory layout of a process with 2 threads ? What is the memory layout a process with 2 child process ?
7. If we declare a variable in the thread handler of 1st thread, will it be accessible accessible to 2nd thread ?
8. If we declare one variable locally in process and another globally in process, which one will be accessible to its threads ? Will those variable be available in child process also ?
9. Is it better to design a multi-threaded application or multi-process application ?
10. When should we need to go for multi-thread design and when should we go for a multi-process design ?
11. What is TLS ?
12. Who schedules the processes and who schedules the threads ?
13. Why process considered to be heavy weight ?
14. What are the contents of PCB ? What are the contents of TCB ?
15. How to ensure that thread1 gets terminated before thread2 ?
16. What will happen if we do not reap the zombie process ?
17. What is the use of zombie process ?
18. What are the various ways to terminate a zombie process ?
19. What is the difference between wait() and waitpid() system calls ?
20. Can two zombie process communicate with each other ?
21. How do you decide on the granularity of the lock ?
22. Is it good to have big lock or small lock ?
23. What will happen if a resource is improperly locked ?
24. What is atomicity ?
25. Where are atomic operations useful ?
26. What is spinlock ?
27. What is the use of PID ?
28. What is a process, thread ? What are the differences between process and thread?
29. If there are 2 sequential fork() calls, how many child process will be there ?
30. What is the use of reentrant function in multi-threaded environment ?
31. What is the advantage of using pthreads or POSIX threads ?
32. What are the various thread models and tell the scenario in which the particular thread model is useful / beneficial ?
33. What are the advantages & dis-advantages of 1:N user level threading (thread model)?
34. What is the difference between userspace threads and kernel space threads ?
35. Will a crash of a thread impact the other thread of the process ?
36. What is the difference between pthread_create() and fork() ?
37. What information is shared between a child process and the parent process ?
38. If a parent has 2 threads , will the child process also inherit or have a copy of those 2 threads ?
39. Why a faulty pointer does not crash a process but that of a thread can corrupt the process / other threads of the process ?
40. What is co-operative multitasking and what is pre-emptive multitasking ?
41. How do avoid race conditions in multi-threading
42. What will happen if you call a sleep() in a process or thread ?
43. Will a parent process be given higher priority compared to child process by the linux scheduler ?
44. What is vfork ?
45. What is the common mode of communication between a parent process and child process ? What are the modes of communication between threads ?
46.  Is child process light weight compared to parent process ?
47. What does a fork() call return ?
48. How to terminate a process by programming method ?
49. What are the software models for mulithreaded programming ?
50. What steps are performed during a context switch of a thread and what steps are performed during a context switch of a process ?

Linux Filesystem

Hey all,
The following are the probable questions related to Linux Filesystem that can be discussed.

1. What is the need for Virtual Memory ?
2. What is the difference between the term 'Virtual Memory' and 'Virtual Address Space' ?
3. Can an user space application view the physical address Or Can an user space application access the physical address space ?
4. Is it possible for two different application to have a same virtual address but point to different physical memory ?
5. What are the functionalities performed by _start ?
6. What is the difference between Code section, Data section, ro Data section & BSS section ?
7. What is the expansion of BSS and What is the need for BSS ?
8. What is the size of the Kernel space and that of User space ? Who decides the size of it . Is it dependent/done by Processor or MMU ?
9. Tell one of the etry point to kernel ?
10. Explain the system call mechanism such that the flow is from User space to Kernel space & returning back to User space ?
11. What is the use of SYSENTER ? Does it get executed in Userspace ?
12. What is the use of SYSEXIT ? Does it get executed in Kernelspace ?
13. What is the role of __sys_open ?
14. What is the use of ABI (Application Binary Interface) document ? Who provides that manual ?
15. How do you see the size of an executable file in Linux ?
16. What is the probable size of normal vmlinux ? What kind of sizes have you come across in normal linux and embedded linux scenarios ?
17. What is vmlinux.lds ?
18. Why do you find all addresses to start after '0xC0000000' if you do 'readelf -a vmlinux' ? Can you access those addresses ?
19. What is a FDT (File Descriptor Table) ?
20. Explain the relation between File Descriptor table, Symbol File table, iNode table and harddrive/phy memory ?
21. What command is used to setup/create the relation between the device and inode ?
22. What command/API is used to create an inode for a file ?
23. What is the use of 'file_operations' ? How have you used it ?
24. What is the use of /proc/PID/maps ?
25. What is task_struct ?
26. Explain the relation between file struct,File Descriptor Table(FDT), task_struct, MM_struct, vm_area_struct, Heap, Page Global Directory(PGD), Page table(PT) & user page .
27. What is the use of ioctl fuction ?
28. Explain one level page table address translation between VA and PA with an example ?
29. Explain multi level page table address translation between VA and PA with an example ?
30. Is it better to have less level of page table address translation or more levels of page table address translation ? What is the impact on performance w.r.t memory size and memory access ?
31. What is the difference between malloc and vmalloc ?
32. What is PAE (Physical Address Extension) ?
33. What is Dual Mapping ? Can a user virtual address and kernel virtual address map to the same physical address ?

Linux and Linux Device driver

Linux is one of the very common Operating Systems and hope many would like to have some linux discussion. Here is a collection of questions for our linux and linux device driver related discussion...

1. What is the difference in features between kernel 2.2, 2.4 and 2.6 ?
2. What are Static and Shared libraries ?
3. What is dynamic linking ? What is static linking ?
4. What are the advantages of Dynamic linking or Shared libraries ?
5. Does gcc search for both static and shared libraries ? Which is searched initially by gcc compiler ?
6. What should be done for Shared library based linking in gcc ?
7. What should be done for static library based linking in gcc ?
8. What is object file and what are symbols ?
9. Can you tell the memory layout based on Data,BSS,HEAP and STACK ?
10. What are the ways in which linux kernel can be compiled ?
11. How will get the driver added into the kernel ? What are Kconfig files ?
12. What is a kernel module ?
13. What is the difference between insmod and modprobe ?
14. How will you list the modules ?
15. How do you get the list of currently available drivers ?
16. How will you Access userspace memory from kernel ? What are the various methods ?
17. What is the use of ioctl(inode,file,cmd,arg) ApI ?
18. What is the use of the poll(file, polltable) API ?
19. What is the use of file->private_data in a device driver structure ?
20. What is a device number ?
21. What are the two types of devices drivers from VFS point of view ?
22. What are character devices ?
23. How does the character device driver adds and remove itself from the kernel ?
What is the use of register_chrdev and unregister_chrdev ?
24. What is the role of interrupts in a device driver ? How are interrupts handled in device driver ?
25. How will you make interrupt handlers as fast as possible ?
26. What are the types of softirqs ?
27. Difference between Timer Softirq and Tasklet Softirq ?
28. What are tasklets ? How are they activated ? when and How are they initialized ?
29. What is task_struct and how are task states maintained ?
30. What is rwlock and spinlock ? Briefly explain about both of them ?
31. When will you use rwlock instead of spinlock ?
32. Can spinlock/rwlock be used in Interrupt handler ?
33. Tell about the Memory Layout of a Process in Linux .
34. How will you trace the system calls made into the kernel of lInux ?
35. What is mmap ? MMAP & malloc ? MMAP & brk ? MMAP adv & dis-adv.
36. Tell the relation between Malloc and MMAP
37. Advantages of MMAP over Read ?
38. Tell the role of brk() in malloc / Tell the relation between heap and brk?
39. Example of using MMAP and MUNMAP in C ?
40. Tell about the method/steps in Linux Kernel Compilation.
41. What is Kmalloc and how does it differ from normal malloc ? or Why can't we use malloc in kernel code ?
42. What happens as soon as a packet arrives from the network in Linux ?
43. What is a stack frame, stack pointer & frame pointer ?
44. What is a profiler ? Which one have you used ?
45. How do you determine the direction of stack growth ?

Linux kernel - I

The below queries can be used for our linux kernel discussion.

1. How are FLIHs and SLIHs termed in Linux ?
2. What is the main drawback for not considering Linux as realtime ?
3. What is the type of scheduler used in Linux Kernel 2.5 ?
4. What are the types of scheduler used in Linux Kernel 2.6 to 2.6.23 and after Linux kernel 2.6.23 ?
5. CFS scheduler in Linux is based on red-black tree - True / False ?
6. O(1) scheduler in Linux is based on run queues - True / False ?
7. Is the architecture of linux kernel monolithic / microkernel ?
8. How will you trace the system calls made into the kernel of lInux ?
9. Tell about the Linux Kernel Compilation method ?
10. What is 'make mrproper' and how is it different from 'make clean' ?
11. What is Kmalloc and how does it differ from normal malloc ? or Why can't we use malloc in kernel code ?
12. Does the scheduler assign a zombie state to a process ?
13. Brief up 'vmalloc' vs 'kmalloc' ?
14. Brief up 'malloc' vs 'kmalloc' ?
15. How modules begin and end in LInux ? Tell the difference between Modules and Program ?
16. What is mmap ?
17. What are the advantages of mmap over read ?
18. Most of Unix kernels are monolithic - True / False ?
19. Why is microkernel slower than monolithic kernel ?
20. What are the advantges of microkernel over monolithic kernel ?
21. What is a 'Module' ?
22. What are the main advantages of using a 'Module' ?
23. Once linked in, the object code of a 'module' is equivalent to the object code of the statically linked kernel - True / False ?
24. What are the limitations of hard links / What are advantages of soft links ?
25. Unix Kernels are Reentrant - True / False ?
26. What is Kernel Control Path ?
27. What is the drawback in using semaphore for synchronization ? How does spinlock help in overcoming it ?
28. What does a semaphore consist of ? and What does a spinlock consist of ?
29. Why spinlocks are useless in uniprocessor systems ?
30. What are the two kinds of system events ?

Boot loader

Here are boot loader related questions that are of great interest and that can be used for our discussions.... Check it out !

1. What are the various boot loaders that you have worked on ?
2. Where is the boot loader present in an embedded system design ?
3. In general, what does the boot loader do ?
4. What is the role of boot loader in embedded systems ?
5. How will you handle a scenario in which the boot software is erased/corrupted ?
6. How will you handle boot software erasure/corruption scenario if Boot ROM is not available ?
7. What do you mean by bootstrap loader and what does it do ?
8. Is booting different from bootstrapping ?
9. When the computer is powered ON, it does not have OS it in neither ROM nor RAM - True/False ?
10. What is a second-stage boot loader ?
11. Do LILO/GRUB/Syslinux belong to either first stage boot loader(small program) or second-stage boot loaders ?
12. What is network booting ?
13. What is Chain loading or Multi-stage boot loader ?
14. Can you brief up the boot sequence of a normal desktop computer ?
15. Tell about OMAP CPU booting ?
16. What are the most common boot modes of DSP processor ?
17. Give few examples for systems that use Host Port(HPI Boot) for DSP booting ?
18. How will you put U-Boot into the target board ?
19. TFTP is a stripped down version of FTP that does not require authentication - True/False ?
20. Why do you need 2 stage boot process in OMAP processor ?
21. Can you give a highlevel view of Linux Boot process ?
22. What is the role of MBR and its relation with BIOS ?
23. Where is the MBR located ?
24. What is the structure of MBR ?
25. The secondary, or second-stage, boot loader could be more aptly called the kernel loader - True / False
26. What is the relation between GRUB and filesystem while booting ? or Main Difference between LILO and GRUB ?
27. What is the difference between zImage and bzImage ?
28. What is the role of initrd/Initial RAM disk ?
29. What is the role of initrd/Initial RAM disk in Embedded systems ?
30. Can you tell about the major function-level flow for Linux i386 booting ?
31. Does GRUB involve a 3-stage boot loading ? If yes, what are they . Brief it ?

Hope this list will help in equipping yourself for few of major interview questions related with boot loaders :-)