Re: [PATCH 1/2] pid: add pidfd_open()

On 05/15, Oleg Nesterov wrote:

On 05/15, Christian Brauner wrote:

...

+SYSCALL_DEFINE2(pidfd_open, pid_t, pid, unsigned int, flags) +{

• int fd, ret;
• struct pid *p;
• struct task_struct *tsk;
• if (flags)

• return -EINVAL;
  

• if (pid <= 0)

• return -EINVAL;
  

• p = find_get_pid(pid);
• if (!p)

• return -ESRCH;
  

• rcu_read_lock();
• tsk = pid_task(p, PIDTYPE_PID);

You do not need find_get_pid() before rcu_lock and put_pid() at the end. You can just do find_vpid() under rcu_read_lock().

Ah, sorry. Somehow I forgot you need to call pidfd_create(pid), you can't do this under rcu_read_lock().

So I was wrong, you can't avoid get/put_pid.

Oleg.