[tip: sched/core] sched/core: Update task_prio() function header

[tip-bot2 for Dietmar Eggemann]

The following commit has been merged into the sched/core branch of tip:

Commit-ID:     075a28439d0c8eb6d3c799e1eed24bb9bc7750cd
Gitweb:        https://git.kernel.org/tip/075a28439d0c8eb6d3c799e1eed24bb9bc7750cd
Author:        Dietmar Eggemann <dietmar.eggemann@xxxxxxx>
AuthorDate:    Thu, 28 Jan 2021 14:10:40 +01:00
Committer:     Peter Zijlstra <peterz@xxxxxxxxxxxxx>
CommitterDate: Mon, 01 Feb 2021 15:31:39 +01:00

sched/core: Update task_prio() function header

The description of the RT offset and the values for 'normal' tasks needs
update. Moreover there are DL tasks now.
task_prio() has to stay like it is to guarantee compatibility with the
/proc/<pid>/stat priority field:

  # cat /proc/<pid>/stat | awk '{ print $18; }'

Signed-off-by: Dietmar Eggemann <dietmar.eggemann@xxxxxxx>
Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
Link: https://lkml.kernel.org/r/20210128131040.296856-4-dietmar.eggemann@xxxxxxx
---
 kernel/sched/core.c | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 625ec1e..be3a956 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -5602,8 +5602,12 @@ SYSCALL_DEFINE1(nice, int, increment)
  * @p: the task in question.
  *
  * Return: The priority value as seen by users in /proc.
- * RT tasks are offset by -200. Normal tasks are centered
- * around 0, value goes from -16 to +15.
+ *
+ * sched policy         return value   kernel prio    user prio/nice
+ *
+ * normal, batch, idle     [0 ... 39]  [100 ... 139]          0/[-20 ... 19]
+ * fifo, rr             [-2 ... -100]     [98 ... 0]  [1 ... 99]
+ * deadline                     -101             -1           0
  */
 int task_prio(const struct task_struct *p)
 {