内核线程和用户程序的优先级的问题；请教高手

请教下各位高手，默认情况下 linux 里内核线程的优先级是不是始终比应用程序的优先级高？
我试着将内核进程和应用程序的优先级使用 cat /proc/pid/stat 打印出来看，结果如下：
root@am335x-evm:~# ./procstat 1
                 pid: 1
               tcomm: (init)
               state: S
                ppid: 0
                pgid: 1
                 sid: 1
              tty_nr: 0
            tty_pgrp: -1
               flags: 4194560
             min_flt: 54
            cmin_flt: 19277
             maj_flt: 97
            cmaj_flt: 477
               utime: 0.090000
               stime: 5.550000
              cutime: 0.410000
              cstime: 1.420000
            priority: 20
                nice: 0
        
         rt_priority: 0
              policy: 0
root@am335x-evm:~# ./procstat 682
                 pid: 682
               tcomm: (HMI_V2)
               state: S
                ppid: 1
                pgid: 628
                 sid: 628
              tty_nr: 0
            tty_pgrp: -1
               flags: 4194560
             min_flt: 5014
            cmin_flt: 1497
             maj_flt: 3248
            cmaj_flt: 455
               utime: 3756.070000
               stime: 573.020000
              cutime: 0.040000
              cstime: 0.160000
            priority: 1
                nice: -19
         
                 cpu: 0
         rt_priority: 0
              policy: 0从上面可以看出：
内核线程 init 其 priority 值为20，nice值为0；而应用程序 HMI_V2 其 priority 值为 1，nice值为 -19；我的疑惑是这两个值是如何决定优先级的？我之前的理解是，如果都是用户程序，则可通过 renice 调整其 nice值，值越小优先级就越高；但这个 priority 的值又该如何理解？请各位大侠赐教。