From: Cyril Hrubis chrubis@suse.cz

stable inclusion from stable-v4.19.308 commit 1f80bc015277247c9fd9646f7c21f1c728b5d908 category: bugfix bugzilla: https://gitee.com/openeuler/kernel/issues/I9K4H3

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?h=l...

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[ Upstream commit c1fc6484e1fb7cc2481d169bfef129a1b0676abe ]

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 Signed-off-by: Petr Vorel pvorel@suse.cz Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org Signed-off-by: Cheng Yu serein.chengyu@huawei.com --- kernel/sched/rt.c | 3 +++ 1 file changed, 3 insertions(+)

diff --git a/kernel/sched/rt.c b/kernel/sched/rt.c index 5dff9a6fe2cf..d98adf048bb6 100644 --- a/kernel/sched/rt.c +++ b/kernel/sched/rt.c @@ -2732,6 +2732,9 @@ int sched_rr_handler(struct ctl_table *table, int write, 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);