Use prctl to name the thread

For multi-threaded applications, if you can name each thread, the convenience of debugging is self-evident.
Today, I read the weekly report on lwn and saw someone adding the interface named by prctl to other threads in the process. I learned that the interface named for the thread already exists, then write the following verification code:

#include
#include
#include
void* tmain(void *arg)
{
char name[32]; 
prctl(PR_SET_NAME, (unsigned long)"xx"); 
prctl(PR_GET_NAME, (unsigned long)name);
printf("%s/n", name);
while (1)
sleep(1);
}
int main(void)
{
pthread_t tid;
pthread_create(&tid, NULL, tmain, NULL);
pthread_join(tid, NULL);
return 0;
}

Compile and run:

Xiaosuo @ gentux test $ GCC t_threadname.c-l pthread
Xiaosuo @ gentux test $./A. Out
Xx

On another terminal, find the PID of A. out through PS:

Xiaosuo @ gentux test $ PS aux | grep A. Out
Xiaosuo 29882 0.0 0.0 14144 pts/6 SL +./A. Out

Check whether the name works:

Xiaosuo @ gentux test $ CD/proc/29882/task/
Xiaosuo @ gentux task $ ls
29882 29883
Xiaosuo @ gentux task $ CD 29883/
Xiaosuo @ gentux 29883 $ cat ticket line
./A. outxiaosuo @ gentux 29883 $

A little depressing. The line display is still./A. Out. Check the prctl return value through the XX and strace printed at run time to confirm that the prctl is indeed running successfully. I suspect that this name can only be obtained through prctl. It is a bit lost, but it is still unwilling. View PS man and experiment, and finally find "XX ":

Xiaosuo @ gentux 29883 $ PS-l-P 29882
PID lwp tty time cmd
29882 29882 pts/6 00:00:00 A. Out
29882 29883 pts/6 00:00:00 xx

After strace knows that this "XX" is actually hidden in stat and status:

Xiaosuo @ gentux 29883 $ cat stat
29883 (XX) s 7168 29882 7168 34822 29882 11 0 0 0 2 0 0 20 0 2 0 4202560 28515372 14483456 136 18446744073709551615 4194304 4196620 140735304261728 18446744073709551615 0 0 0 0 140435890519585 0 0 0-1 1 0 0 0 0 0
Xiaosuo @ gentux 29883 $ cat status
Name: xx
State: S (sleeping)
Tgid: 29882
PID: 29883
Ppid: 7168
Tracerpid: 0
UID: 1000 1000 1000 1000
GID: 1000 1000 1000 1000
Fdsize: 256.
Groups: 10 18 1000 1001 1005
Vmpeak: 14144 KB
Vmsize: 14144 KB
Vmlck: 0 KB
Vmhwm: 548 KB
Vmrss: 544 KB
Vmdata: 8388 KB
Vmstk: 84 KB
Vmexe: 4 kb
Vmlib: 1528 KB
Vmpte: 32 KB
Threads: 2
Sigq: 1/40960
Sigpnd: 0000000000000000
Shdpnd: 0000000000000000
Sigblk: 0000000000000000
Sigign: 0000000000000000
Sigcgt: 0000000180000000
Capinh: 0000000000000000
Cappr: 0000000000000000
Capeff: 0000000000000000
Capbnd: fffffffffffffeff
Voluntary_ctxt_switches: 4447
Nonvoluntary_ctxt_switches: 0

Verified! :)