Is it safe to retrieve userspace PID using current->pid in Linux Driver?

Question

I would like to retrieve caller process' PID (Userspace) in Linux Driver.

At first, I could find pid attribute so easy from the struct task_struct in Linux Source Code (include/linux/sched.h) I used current->pid to retrieve userspace PID.

However, I read some articles telling that the pid in Kernel and Userspace context are different. In other words, so called userspace PID is in fact tgid which is also an attribute of struct task_struct.

Moreover, when I look into the source code getpid() system call expecting this should return task_struct.pid or task_struct.tgid, it turns out that it returned unexpected function- task_tgid_vnr- ultimately uses the signal inside task_struct.

As my ultimate goal was so simple- to find out the exact same PID retrieved from getpid() system call in Linux kernel- I am very confused.

In conclusion, among all the options above, which way is the recommended way to retrieve the caller process' userspace PID?