linux-kernel - [PATCH v4] sched/rt: fix the case where sched_rt_period

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Date:   Tue, 17 May 2022 14:29:18 +0800
From:   Yajun Deng <yajun.deng@...ux.dev>
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, Yajun Deng <yajun.deng@...ux.dev>
Subject: [PATCH v4] sched/rt: fix the case where sched_rt_period_us is negative

The proc_dointvec() is for integer, but sysctl_sched_rt_period is a
unsigned integer, proc_dointvec() would convert negative number into
positive number. So both proc_dointvec() and sched_rt_global_validate()
aren't return error even if we set a negative number.

Use proc_dointvec_minmax() instead of proc_dointvec() and use extra1
limit the minimum value for sched_rt_period_us/sched_rt_runtime_us.

Make sysctl_sched_rt_period integer to match proc_dointvec_minmax().

v4:
 - Make sysctl_sched_rt_period integer (Valentin Schneider)
v2:
 - Remove sched_rr_timeslice_ms related changes (Valentin Schneider)

Fixes: d0b27fa77854 ("sched: rt-group: synchonised bandwidth period")
Signed-off-by: Yajun Deng <yajun.deng@...ux.dev>
---
 kernel/sched/rt.c    | 11 +++++------
 kernel/sched/sched.h |  2 +-
 2 files changed, 6 insertions(+), 7 deletions(-)

diff --git a/kernel/sched/rt.c b/kernel/sched/rt.c
index 8c9ed9664840..cafc580edbe4 100644
--- a/kernel/sched/rt.c
+++ b/kernel/sched/rt.c
@@ -16,7 +16,7 @@ struct rt_bandwidth def_rt_bandwidth;
  * period over which we measure -rt task CPU usage in us.
  * default: 1s
  */
-unsigned int sysctl_sched_rt_period = 1000000;
+int sysctl_sched_rt_period = 1000000;
 
 /*
  * part of the period that we allow rt tasks to run in us.
@@ -34,9 +34,10 @@ static struct ctl_table sched_rt_sysctls[] = {
 	{
 		.procname       = "sched_rt_period_us",
 		.data           = &sysctl_sched_rt_period,
-		.maxlen         = sizeof(unsigned int),
+		.maxlen         = sizeof(int),
 		.mode           = 0644,
 		.proc_handler   = sched_rt_handler,
+		.extra1		= SYSCTL_ONE,
 	},
 	{
 		.procname       = "sched_rt_runtime_us",
@@ -44,6 +45,7 @@ static struct ctl_table sched_rt_sysctls[] = {
 		.maxlen         = sizeof(int),
 		.mode           = 0644,
 		.proc_handler   = sched_rt_handler,
+		.extra1		= SYSCTL_NEG_ONE,
 	},
 	{
 		.procname       = "sched_rr_timeslice_ms",
@@ -2960,9 +2962,6 @@ static int sched_rt_global_constraints(void)
 #ifdef CONFIG_SYSCTL
 static int sched_rt_global_validate(void)
 {
-	if (sysctl_sched_rt_period <= 0)
-		return -EINVAL;
-
 	if ((sysctl_sched_rt_runtime != RUNTIME_INF) &&
 		((sysctl_sched_rt_runtime > sysctl_sched_rt_period) ||
 		 ((u64)sysctl_sched_rt_runtime *
@@ -2993,7 +2992,7 @@ static int sched_rt_handler(struct ctl_table *table, int write, void *buffer,
 	old_period = sysctl_sched_rt_period;
 	old_runtime = sysctl_sched_rt_runtime;
 
-	ret = proc_dointvec(table, write, buffer, lenp, ppos);
+	ret = proc_dointvec_minmax(table, write, buffer, lenp, ppos);
 
 	if (!ret && write) {
 		ret = sched_rt_global_validate();
diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h
index 1f97f357aacd..1cb4d47b3e47 100644
--- a/kernel/sched/sched.h
+++ b/kernel/sched/sched.h
@@ -115,7 +115,7 @@ extern long calc_load_fold_active(struct rq *this_rq, long adjust);
 
 extern void call_trace_sched_update_nr_running(struct rq *rq, int count);
 
-extern unsigned int sysctl_sched_rt_period;
+extern int sysctl_sched_rt_period;
 extern int sysctl_sched_rt_runtime;
 extern int sched_rr_timeslice;
 
-- 
2.25.1