CODEWITHSUNDEEP
clinuxmultithreading
liv2hak
liv2hak

Reputation: 14970

Linux threads and processes

I have a simple question about Linux threads and processes.

The process in Linux has a separate virtual address space which consists of:

- stack
- heap
- bss
- code/text
- data

A process can have multiple threads inside them. I understand that they do share the address space of the process.

However, since the function calls that are executed by different threads can be different, does a thread have a separate stack segment?

Upvotes: 3

Views: 896

Answers (2)

Jim Lewis
Jim Lewis

Reputation: 45025

Yes, under the POSIX threading model, each thread has its own stack.

Upvotes: 1

Wu Yongzheng
Wu Yongzheng

Reputation: 1707

  1. Threads share all the memory segments, including the stack segment.
  2. Each thread has a separate stack.

Both statements are true. I know they sound like a contradiction.

The first thread's stack uses the so-called "stack segment". It's allocated by the kernel.

# cat /proc/self/maps
...
7fffbe0b0000-7fffbe0d1000 rw-p 00000000 00:00 0                          [stack]
...

Threads created later (e.g. created by pthread_create() or clone(CLONE_VM)) use the heap (or private anonymous mmap which is the same as heap in every ways) as their stack. It's allocated by the user program and passed to clone().

In short, each thread uses a separate stack. All the threads can read/write every other threads' stack.

Upvotes: 2

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