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Subject[tip:sched/core] sched/core: Document that RT task priorities are 1...99
Commit-ID:  37a8f8590f307db8f8cfa62dfd82b3fc0978607c
Gitweb: https://git.kernel.org/tip/37a8f8590f307db8f8cfa62dfd82b3fc0978607c
Author: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
AuthorDate: Wed, 3 Apr 2019 23:08:21 +0200
Committer: Ingo Molnar <mingo@kernel.org>
CommitDate: Tue, 16 Apr 2019 10:06:08 +0200

sched/core: Document that RT task priorities are 1...99

John identified three files which claim that RT task priorities start at
zero. As far as I understand, 0 is used for DL and has nothing to do
wihich RT priorities as identified by the RT policy.

Correct the comment, valid RT priorities are in the range from 1 to 99.

Reported-by: John Ogness <john.ogness@linutronix.de>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/20190403210821.10916-1-bigeasy@linutronix.de
Signed-off-by: Ingo Molnar <mingo@kernel.org>
---
Documentation/scheduler/sched-rt-group.txt | 2 +-
include/linux/sched/prio.h | 2 +-
kernel/sched/cpupri.h | 2 +-
3 files changed, 3 insertions(+), 3 deletions(-)

diff --git a/Documentation/scheduler/sched-rt-group.txt b/Documentation/scheduler/sched-rt-group.txt
index d8fce3e78457..23f8f8465a77 100644
--- a/Documentation/scheduler/sched-rt-group.txt
+++ b/Documentation/scheduler/sched-rt-group.txt
@@ -175,7 +175,7 @@ get their allocated time.

Implementing SCHED_EDF might take a while to complete. Priority Inheritance is
the biggest challenge as the current linux PI infrastructure is geared towards
-the limited static priority levels 0-99. With deadline scheduling you need to
+the limited static priority levels 1-99. With deadline scheduling you need to
do deadline inheritance (since priority is inversely proportional to the
deadline delta (deadline - now)).

diff --git a/include/linux/sched/prio.h b/include/linux/sched/prio.h
index 7d64feafc408..6986c3235684 100644
--- a/include/linux/sched/prio.h
+++ b/include/linux/sched/prio.h
@@ -8,7 +8,7 @@

/*
* Priority of a process goes from 0..MAX_PRIO-1, valid RT
- * priority is 0..MAX_RT_PRIO-1, and SCHED_NORMAL/SCHED_BATCH
+ * priority is 1..MAX_RT_PRIO-1, and SCHED_NORMAL/SCHED_BATCH
* tasks are in the range MAX_RT_PRIO..MAX_PRIO-1. Priority
* values are inverted: lower p->prio value means higher priority.
*
diff --git a/kernel/sched/cpupri.h b/kernel/sched/cpupri.h
index 7dc20a3232e7..40257a97fb8f 100644
--- a/kernel/sched/cpupri.h
+++ b/kernel/sched/cpupri.h
@@ -5,7 +5,7 @@
#define CPUPRI_INVALID -1
#define CPUPRI_IDLE 0
#define CPUPRI_NORMAL 1
-/* values 2-101 are RT priorities 0-99 */
+/* values 2-101 are RT priorities 1-99 */

struct cpupri_vec {
atomic_t count;
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