将创建多少个进程和线程? [英] How many processes and threads will be created?
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问题描述
我有这段代码,并试图了解由此将创建多少个进程和线程:
I have this code and trying to understand how many process and threads will be created from this:
pid t pid;
pid = fork();
if (pid == 0) { /* child process */
fork();
thread create( . . .);
}
fork();
我认为它从if循环内的fork创建了2个线程.和8个过程?但是我不确定那是否正确
I think it creates 2 threads, from the fork inside the if loop. and 8 processes? But Im not sure if thats right
推荐答案
实际上,应该有8个线程和6个进程.
Actually, there should be 8 threads and 6 processes.
以下是清楚说明图表:
1) after first fork():
|------------------- child of p0 [p1]
---|------------------- parent [p0]
2) after second fork():
|--------------- child of p1 [p2]
|---|--------------- [p1]
---|------------------- [p0]
3) after pthread_create():
----------- thread 1 of p2 [p2t1]
|---/----------- thread 0 of p2 [p2t0]
| ----------- thread 1 of p1 [p1t1]
|---|---/----------- thread 0 of p1 [p1t0]
---|------------------- [p0]
4) after third fork():
|------------ child of p2 [p5]
| ------ [p2t1]
|-|-----/------ [p2t0]
| |---------- child of p1 [p4]
| | ------ [p1t1]
|---|---|---/------ [p1t0]
| |------------ child of p0 [p3]
---|-----|------------ [p0]
重要:请记住 fork(2) call仅克隆执行该线程的线程,因此进程4 [p4]只有一个线程(与进程5 [p5]相同).
important: Remember that the fork(2) call clones just the thread which executed it, thus process 4 [p4] has only one thread (same apply to process 5[p5]).
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