Process-based forking and thread-based forking are two different semantics for fork() system call on multithreading.

1. Draw a process tree for both semantics (use P, SP, SSP, to indicate the main process, sub-process, sub-sub-process, ; use P(n) to indicate a process with n extra threads.);

2. For each case, how many new processes have been created? and how many extra threads have been created?

pid_t pid;

pid = fork();

if (pid == 0) { /* child process */

fork();

thread_create( . . .);

}

else {

thread_create( . . .); }

fork();