Threads

Question

Since every thread can access every memory address within the process’ address space, one thread can read, write, or even wipe out another thread’s stack.

I am not getting the above statement, stack is specific to a thread then how we can access other thread's stack through Process' address space? 

Comments

assume a global variable present in the code it is visible in all the stacks hence one evil thread can play with that variable and corrupt it that will get replicated in the stacks of all the threads (threads share the data segment )

but as u r the programmer u will never write code in such a manner  :)

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Global Variables are stored in Heap not in Stack, so Threads can access global variable as Heap is shared.

Answer 1

Threads are lightwieight process . Each threads share same address space of process . There are some really great advanatges if we comapre threads as compared to process . Ecah threads have its own register , stack but they all share file and code section . Threads share address space . Even one thread can guide to other threads (ASSISTANCE ) which is not posiible in process .  Threads are found to be advanatgeous where we need to handle multiple request . eg in a client server  application  A server can make use of threads and handle multiple request with multiple threads at the same time . but along with this advanatges , we have only  1 disadvantges ,

it may happen that thread 1 may wirite on thread 2 stack ,-- PROTECTION IS VIOLATED . but this is a rare condition.

(NOTE : each threads have its own stack beacuse they are executing task which are independnt of each other so they need to store there execution history of there task on stack )

Answer 2

Different threads in a process are not quite as independent as different processes. All threads have exactly the same address space, which means that they also share the same global variables.

Refer :http://www.cs.vu.nl/~ast/books/mos2/sample-2.pdf 

Comments

That's Okay! But how can it access Other thread's STACK ?