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[SRU,M,1/2] sched/rt: sysctl_sched_rr_timeslice show default timeslice after reset

Message ID 20240410112920.33436-2-guoqing.jiang@canonical.com
State New
Headers show
Series Fix proc_sched_rt01 issue in LTP | expand

Commit Message

Guoqing Jiang April 10, 2024, 11:29 a.m. UTC 
From: Cyril Hrubis <chrubis@suse.cz>

BugLink: https://bugs.launchpad.net/bugs/2057734

The sched_rr_timeslice can be reset to default by writing value that is
<= 0. However after reading from this file we always got the last value
written, which is not useful at all.

$ echo -1 > /proc/sys/kernel/sched_rr_timeslice_ms
$ cat /proc/sys/kernel/sched_rr_timeslice_ms
-1

Fix this by setting the variable that holds the sysctl file value to the
jiffies_to_msecs(RR_TIMESLICE) in case that <= 0 value was written.

Signed-off-by: Cyril Hrubis <chrubis@suse.cz>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Petr Vorel <pvorel@suse.cz>
Acked-by: Mel Gorman <mgorman@suse.de>
Tested-by: Petr Vorel <pvorel@suse.cz>
Link: https://lore.kernel.org/r/20230802151906.25258-3-chrubis@suse.cz
(cherry picked from commit c1fc6484e1fb7cc2481d169bfef129a1b0676abe)
Signed-off-by: Guoqing Jiang <guoqing.jiang@canonical.com>
---
 kernel/sched/rt.c | 3 +++
 1 file changed, 3 insertions(+)
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Patch

diff --git a/kernel/sched/rt.c b/kernel/sched/rt.c
index 590abc1a013d..904dd8534597 100644
--- a/kernel/sched/rt.c
+++ b/kernel/sched/rt.c
@@ -3066,6 +3066,9 @@  static int sched_rr_handler(struct ctl_table *table, int write, void *buffer,
 		sched_rr_timeslice =
 			sysctl_sched_rr_timeslice <= 0 ? RR_TIMESLICE :
 			msecs_to_jiffies(sysctl_sched_rr_timeslice);
+
+		if (sysctl_sched_rr_timeslice <= 0)
+			sysctl_sched_rr_timeslice = jiffies_to_msecs(RR_TIMESLICE);
 	}
 	mutex_unlock(&mutex);