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Subject[PATCH 4/2] sched/cpupri: Add CPUPRI_HIGHER

Add CPUPRI_HIGHER above the RT99 priority to denote the CPU is in use
by higher priority tasks (specifically deadline).

XXX: we should probably drive PUSH-PULL from cpupri, that would
automagically result in an RT-PUSH when DL sets cpupri to CPUPRI_HIGHER.

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
---
kernel/sched/cpupri.c | 10 ++++++++--
kernel/sched/cpupri.h | 3 ++-
kernel/sched/deadline.c | 3 +++
3 files changed, 13 insertions(+), 3 deletions(-)

--- a/kernel/sched/cpupri.c
+++ b/kernel/sched/cpupri.c
@@ -11,7 +11,7 @@
* This code tracks the priority of each CPU so that global migration
* decisions are easy to calculate. Each CPU can be in a state as follows:
*
- * (INVALID), NORMAL, RT1, ... RT99
+ * (INVALID), NORMAL, RT1, ... RT99, HIGHER
*
* going from the lowest priority to the highest. CPUs in the INVALID state
* are not eligible for routing. The system maintains this state with
@@ -19,7 +19,7 @@
* in that class). Therefore a typical application without affinity
* restrictions can find a suitable CPU with O(1) complexity (e.g. two bit
* searches). For tasks with affinity restrictions, the algorithm has a
- * worst case complexity of O(min(100, nr_domcpus)), though the scenario that
+ * worst case complexity of O(min(101, nr_domcpus)), though the scenario that
* yields the worst case search is fairly contrived.
*/
#include "sched.h"
@@ -37,6 +37,8 @@
* 50 49 49 50
* ...
* 99 0 0 99
+ *
+ * 100 100 (CPUPRI_HIGHER)
*/
static int convert_prio(int prio)
{
@@ -54,6 +56,10 @@ static int convert_prio(int prio)
case MAX_RT_PRIO-1:
cpupri = CPUPRI_NORMAL; /* 0 */
break;
+
+ case MAX_RT_PRIO:
+ cpupri = CPUPRI_HIGHER; /* 100 */
+ break;
}

return cpupri;
--- a/kernel/sched/cpupri.h
+++ b/kernel/sched/cpupri.h
@@ -1,10 +1,11 @@
/* SPDX-License-Identifier: GPL-2.0 */

-#define CPUPRI_NR_PRIORITIES MAX_RT_PRIO
+#define CPUPRI_NR_PRIORITIES (MAX_RT_PRIO+1)

#define CPUPRI_INVALID -1
#define CPUPRI_NORMAL 0
/* values 1-99 are for RT1-RT99 priorities */
+#define CPUPRI_HIGHER 100

struct cpupri_vec {
atomic_t count;
--- a/kernel/sched/deadline.c
+++ b/kernel/sched/deadline.c
@@ -1364,6 +1364,8 @@ static void inc_dl_deadline(struct dl_rq

if (dl_rq->earliest_dl.curr == 0 ||
dl_time_before(deadline, dl_rq->earliest_dl.curr)) {
+ if (dl_rq->earliest_dl.curr == 0)
+ cpupri_set(&rq->rd->cpupri, rq->cpu, CPUPRI_HIGHER);
dl_rq->earliest_dl.curr = deadline;
cpudl_set(&rq->rd->cpudl, rq->cpu, deadline);
}
@@ -1381,6 +1383,7 @@ static void dec_dl_deadline(struct dl_rq
dl_rq->earliest_dl.curr = 0;
dl_rq->earliest_dl.next = 0;
cpudl_clear(&rq->rd->cpudl, rq->cpu);
+ cpupri_set(&rq->rd->cpupri, rq->cpu, rq->rt.highest_prio.curr);
} else {
struct rb_node *leftmost = dl_rq->root.rb_leftmost;
struct sched_dl_entity *entry;
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