Linux Threads

• Linux provides the $fork()$ system call with the traditional functionality of duplicating a process. Linux also provides the ability to create threads using the $clone()$ system call.
• However, Linux does not distinguish between processes and threads. In fact, Linux generally uses the term task -rather than process or thread - when referring to a flow of control within a program.
• When $clone()$ is invoked, it is passed a set of flags, which determine how much sharing is to take place between the parent and child tasks. Some of these flags are listed in Fig. 4.9 below:

  Figure 4.9: Some flags for $clone()$ system call.

  
• if $clone()$ is passed the flags above in the Fig. 4.9, the parent and child tasks will share the same mentioned resources. Using $clone()$ in this fashion is equivalent to creating a thread.
• However, if none of these flags are set when $clone()$ is invoked, no sharing takes place, resulting in functionality similar to that provided by the $fork()$ system call.