Linux processes and threads

* Process status

TASK_RUNNING // run
TASK_INTERRUPTIBLE // The process can receive OS signals.
TASK_UNINTERRUPTIBLE // at this time, the process does not receive OS signals.
TASK_ZOMBIE // process ends, resources are released, and process descriptor is not released.
TASK_STOPPED // process stops running

* Kernel space and user space

Kernel space is the memory area for the Kernel and device drivers to run.
User space is the region where normal applications are running.

Pmap-x <pid> shows the memory usage of a process;
Lsof-a-p <pid> View the file opened by the process.
Ps-Lf <pid> shows the number of threads of a process.