我正在嘗試使用clone()創建一個新線程.使用以下代碼(…)：

#include

#include

#include

#define _SCHED_H 1

#define __USE_GNU 1

#include

#define STACK_SIZE 4096

int func(void *arg) {

printf("Inside func.\n");

sleep(1);

printf("Terminating func...\n");

return 0;

}

int main() {

printf("This process pid: %u\n", getpid());

char status_file[] = "/proc/self/status";

void *child_stack = malloc(STACK_SIZE);

int thread_pid;

printf("Creating new thread...\n");

thread_pid = clone(&func, child_stack+STACK_SIZE, CLONE_SIGHAND|CLONE_FS|CLONE_VM|CLONE_FILES, NULL);

printf("Done! Thread pid: %d\n", thread_pid);

FILE *fp = fopen(status_file, "rb");

printf("Looking into %s...\n", status_file);

while(1) {

char ch = fgetc(fp);

if(feof(fp)) break;

printf("%c", ch);

}

fclose(fp);

getchar();

return 0;

}

我得到以下內容：

This process pid: 10839

Creating new thread...

Done! Thread pid: 10840

Inside func.

Looking into /proc/self/status...

Name: threadTest02

State: R (running)

Tgid: 10839

Pid: 10839

PPid: 4777

TracerPid: 0

Uid: 1000 1000 1000 1000

Gid: 1000 1000 1000 1000

FDSize: 256

Groups: 4 20 24 27 30 46 107 123 124 1000

VmPeak: 4300 kB

VmSize: 4300 kB

VmLck: 0 kB

VmPin: 0 kB

VmHWM: 356 kB

VmRSS: 356 kB

VmData: 188 kB

VmStk: 136 kB

VmExe: 4 kB

VmLib: 1884 kB

VmPTE: 32 kB

VmSwap: 0 kB

Threads: 1

SigQ: 0/22869

SigPnd: 0000000000000000

ShdPnd: 0000000000000000

SigBlk: 0000000000000000

SigIgn: 0000000000000000

SigCgt: 0000000000000000

CapInh: 0000000000000000

CapPrm: 0000000000000000

CapEff: 0000000000000000

CapBnd: ffffffffffffffff

Cpus_allowed: 3

Cpus_allowed_list: 0-1

Mems_allowed: 00000000,00000001

Mems_allowed_list: 0

voluntary_ctxt_switches: 1

nonvoluntary_ctxt_switches: 1

Terminating func...

那么,簡而言之,我的計劃做了什么？它使用clone創建一個新線程并打印其/ proc / self / status,以便我可以看到它的狀態.由于我的線程休眠1秒,因此在打印/ proc / self / status時它仍處于活動狀態.

但是,至少有兩件事使我的線程不像普通線程.首先,正如您在上面看到的,進程’pid是10839而我的線程的pid是10840.因此,進程和我的線程沒有相同的pid,就像在一個共同的線程中一樣.其次,即使在我的線程創建之后,我的進程’/ proc / self / status文件的Threads：字段仍然是1.所以,我的線程似乎不被識別為線程.

我的問題是,我的代碼中缺少什么？我需要做些什么才能使我的線程像普通線程一樣？克隆的第三個參數中是否缺少任何選項？

解決方法:

您可能希望看到標志CLONE_THREAD,它會將新線程放在與調用進程相同的線程組中.

一旦你給了CLONE_THREAD,它將使新線程與調用進程具有相同的pid和ppid.它用于posix線程.以下是我系統的輸出. LWP專欄說這是一個輕量級的過程,具有不同的TID

UID PID PPID LWP C NLWP SZ RSS PSR STIME TTY TIME CMD

anukalp 18398 9638 18398 0 2 464 456 0 10:56 pts/3 00:00:00 ./a.out

anukalp 18398 9638 18399 0 2 464 456 1 10:56 pts/3 00:00:00 ./a.out

此外,/ proc / self / status的輸出發生了變化,我添加了幾個printfs：

[anukalp @ localhost~] $./a.out

This process pid: 18398

Creating new thread...

Done! Thread pid: 18399 /* This is now thread id, available to caller of clone */

getpid(): ad pid: 18399

Inside func.

getpid(): 18398

getppid(): 9638

Looking into /proc/self/status...

Name: a.out

State: R (running)

Tgid: 18398

Pid: 18398

PPid: 9638

TracerPid: 0

Uid: 500 500 500 500

Gid: 500 500 500 500

FDSize: 256

Groups: 7 19 22 80 81 82 83 100 490 500

VmPeak: 1856 kB

VmSize: 1856 kB

VmLck: 0 kB

VmPin: 0 kB

VmHWM: 248 kB

VmRSS: 248 kB

VmData: 168 kB

VmStk: 140 kB

VmExe: 4 kB

VmLib: 1516 kB

VmPTE: 16 kB

VmSwap: 0 kB

Threads: 2

SigQ: 1/14050

SigPnd: 0000000000000000

ShdPnd: 0000000000000000

SigBlk: 0000000000000000

SigIgn: 0000000000000000

SigCgt: 0000000000000000

CapInh: 0000000000000000

CapPrm: 0000000000000000

CapEff: 0000000000000000

CapBnd: ffffffffffffffff

Cpus_allowed: 00000000,000000ff

Cpus_allowed_list: 0-7

voluntary_ctxt_switches: 1

nonvoluntary_ctxt_switches: 0

Inside thread: thread pid = 18398

Inside thread: thread ppid = 9638

請讓我知道這可不可以幫你！

標簽：linux,multithreading,process

來源： https://codeday.me/bug/20190517/1122666.html

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