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Message-Id: <1675245680-2811-1-git-send-email-chensong_2000@189.cn>
Date: Wed, 1 Feb 2023 18:01:20 +0800
From: Song Chen <chensong_2000@....cn>
To: mingo@...hat.com, peterz@...radead.org, juri.lelli@...hat.com,
vincent.guittot@...aro.org, dietmar.eggemann@....com,
rostedt@...dmis.org, bsegall@...gle.com, mgorman@...e.de,
bristot@...hat.com, vschneid@...hat.com
Cc: linux-kernel@...r.kernel.org, Song Chen <chensong_2000@....cn>
Subject: [PATCH] kernel/sched/core: adjust rt_priority accordingly when prio is changed
When a high priority process is acquiring a rtmutex which is held by a
low priority process, the latter's priority will be boosted up by calling
rt_mutex_setprio->__setscheduler_prio.
However, p->prio is changed but p->rt_priority is not, as a result, the
equation between prio and rt_priority is broken, which is:
prio = MAX_RT_PRIO - 1 - rt_priority
It's confusing to the user when it calls sched_getparam, which only
returns rt_priority.
This patch addresses this issue by adjusting rt_priority according to
the new value of prio, what's more, it also returns normal_prio for
CFS processes instead of just a zero.
Signed-off-by: Song Chen <chensong_2000@....cn>
---
kernel/sched/core.c | 10 +++++++---
1 file changed, 7 insertions(+), 3 deletions(-)
diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index bb1ee6d7bdde..1c2c4ada08cc 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -6933,14 +6933,16 @@ EXPORT_SYMBOL(default_wake_function);
static void __setscheduler_prio(struct task_struct *p, int prio)
{
+ p->prio = prio;
+
if (dl_prio(prio))
p->sched_class = &dl_sched_class;
- else if (rt_prio(prio))
+ else if (rt_prio(prio)) {
+ p->rt_priority = MAX_RT_PRIO - 1 - prio;
p->sched_class = &rt_sched_class;
+ }
else
p->sched_class = &fair_sched_class;
-
- p->prio = prio;
}
#ifdef CONFIG_RT_MUTEXES
@@ -8058,6 +8060,8 @@ SYSCALL_DEFINE2(sched_getparam, pid_t, pid, struct sched_param __user *, param)
if (task_has_rt_policy(p))
lp.sched_priority = p->rt_priority;
+ else
+ lp.sched_priority = normal_prio(p);
rcu_read_unlock();
/*
--
2.25.1
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