What resources are shared between threads?

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Recently, I have been asked a question in an interview what's the difference between a process and a thread. Really, I did not know the answer. I thought for a minute and gave a very weird answer.

Threads share the same memory, processes do not. After answering this, the interviewer gave me an evil smile and fired the following questions at me:

Q. Do you know the segments in which a program gets divided?

My answer: yep (thought it was an easy one) Stack, Data, Code, Heap

Q. So, tell me: which segments do threads share?

I could not answer this and ended up in saying all of them.

Please, can anybody present the correct and impressive answers for the difference between a process and a thread?

operating-system multithreading process
13 Answers

Besides global memory, threads also share a number of other attributes (i.e., these attributes are global to a process, rather than specific to a thread). These attributes include the following:

  • process ID and parent process ID;
  • process group ID and session ID;
  • controlling terminal;
  • process credentials (user and group IDs);
  • open file descriptors;
  • record locks created using fcntl();
  • signal dispositions;
  • file system–related information: umask, current working directory, and root directory;
  • interval timers (setitimer()) and POSIX timers (timer_create());
  • System V semaphore undo (semadj) values (Section 47.8);
  • resource limits;
  • CPU time consumed (as returned by times());
  • resources consumed (as returned by getrusage()); and
  • nice value (set by setpriority() and nice()).

Among the attributes that are distinct for each thread are the following:

  • thread ID (Section 29.5);
  • signal mask;
  • thread-specific data (Section 31.3);
  • alternate signal stack (sigaltstack());
  • the errno variable;
  • floating-point environment (see fenv(3));
  • realtime scheduling policy and priority (Sections 35.2 and 35.3);
  • CPU affinity (Linux-specific, described in Section 35.4);
  • capabilities (Linux-specific, described in Chapter 39); and
  • stack (local variables and function call linkage information).

Excerpt From: The Linux Programming Interface: A Linux and UNIX System Programming Handbook , Michael Kerrisk, page 619

user_49906420

In process all threads share system resource like heap Memory etc. while Thread has its own stack

So your ans should be heap memory which all threads share for a process.

user_96527860
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