From 00a95b481eba7e5d98a34b9a66ac141d6439969c Mon Sep 17 00:00:00 2001 From: Juri Lelli Date: Mon, 19 Nov 2018 16:32:01 +0100 Subject: sched/core: Fix PI boosting between RT and DEADLINE tasks [ Upstream commit 740797ce3a124b7dd22b7fb832d87bc8fba1cf6f ] syzbot reported the following warning: WARNING: CPU: 1 PID: 6351 at kernel/sched/deadline.c:628 enqueue_task_dl+0x22da/0x38a0 kernel/sched/deadline.c:1504 At deadline.c:628 we have: 623 static inline void setup_new_dl_entity(struct sched_dl_entity *dl_se) 624 { 625 struct dl_rq *dl_rq = dl_rq_of_se(dl_se); 626 struct rq *rq = rq_of_dl_rq(dl_rq); 627 628 WARN_ON(dl_se->dl_boosted); 629 WARN_ON(dl_time_before(rq_clock(rq), dl_se->deadline)); [...] } Which means that setup_new_dl_entity() has been called on a task currently boosted. This shouldn't happen though, as setup_new_dl_entity() is only called when the 'dynamic' deadline of the new entity is in the past w.r.t. rq_clock and boosted tasks shouldn't verify this condition. Digging through the PI code I noticed that what above might in fact happen if an RT tasks blocks on an rt_mutex hold by a DEADLINE task. In the first branch of boosting conditions we check only if a pi_task 'dynamic' deadline is earlier than mutex holder's and in this case we set mutex holder to be dl_boosted. However, since RT 'dynamic' deadlines are only initialized if such tasks get boosted at some point (or if they become DEADLINE of course), in general RT 'dynamic' deadlines are usually equal to 0 and this verifies the aforementioned condition. Fix it by checking that the potential donor task is actually (even if temporary because in turn boosted) running at DEADLINE priority before using its 'dynamic' deadline value. Fixes: 2d3d891d3344 ("sched/deadline: Add SCHED_DEADLINE inheritance logic") Reported-by: syzbot+119ba87189432ead09b4@syzkaller.appspotmail.com Signed-off-by: Juri Lelli Signed-off-by: Peter Zijlstra (Intel) Signed-off-by: Ingo Molnar Reviewed-by: Daniel Bristot de Oliveira Tested-by: Daniel Wagner Link: https://lkml.kernel.org/r/20181119153201.GB2119@localhost.localdomain Signed-off-by: Sasha Levin --- kernel/sched/core.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) (limited to 'kernel/sched/core.c') diff --git a/kernel/sched/core.c b/kernel/sched/core.c index d81bcc6362ff..14a87c1f3a3a 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -3439,7 +3439,8 @@ void rt_mutex_setprio(struct task_struct *p, int prio) if (dl_prio(prio)) { struct task_struct *pi_task = rt_mutex_get_top_task(p); if (!dl_prio(p->normal_prio) || - (pi_task && dl_entity_preempt(&pi_task->dl, &p->dl))) { + (pi_task && dl_prio(pi_task->prio) && + dl_entity_preempt(&pi_task->dl, &p->dl))) { p->dl.dl_boosted = 1; enqueue_flag |= ENQUEUE_REPLENISH; } else -- cgit v1.2.3 From e9bc62b17b65523f8e714348a652fd8993fad833 Mon Sep 17 00:00:00 2001 From: Shile Zhang Date: Sat, 28 Jan 2017 22:00:49 +0800 Subject: sched/rt: Show the 'sched_rr_timeslice' SCHED_RR timeslice tuning knob in milliseconds [ Upstream commit 975e155ed8732cb81f55c021c441ae662dd040b5 ] We added the 'sched_rr_timeslice_ms' SCHED_RR tuning knob in this commit: ce0dbbbb30ae ("sched/rt: Add a tuning knob to allow changing SCHED_RR timeslice") ... which name suggests to users that it's in milliseconds, while in reality it's being set in milliseconds but the result is shown in jiffies. This is obviously confusing when HZ is not 1000, it makes it appear like the value set failed, such as HZ=100: root# echo 100 > /proc/sys/kernel/sched_rr_timeslice_ms root# cat /proc/sys/kernel/sched_rr_timeslice_ms 10 Fix this to be milliseconds all around. Signed-off-by: Shile Zhang Signed-off-by: Peter Zijlstra (Intel) Cc: Linus Torvalds Cc: Mike Galbraith Cc: Peter Zijlstra Cc: Thomas Gleixner Link: http://lkml.kernel.org/r/1485612049-20923-1-git-send-email-shile.zhang@nokia.com Signed-off-by: Ingo Molnar Signed-off-by: Sasha Levin --- kernel/sched/core.c | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-) (limited to 'kernel/sched/core.c') diff --git a/kernel/sched/core.c b/kernel/sched/core.c index 14a87c1f3a3a..4a0a754f24c8 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -8266,8 +8266,9 @@ int sched_rr_handler(struct ctl_table *table, int write, /* make sure that internally we keep jiffies */ /* also, writing zero resets timeslice to default */ if (!ret && write) { - sched_rr_timeslice = sched_rr_timeslice <= 0 ? - RR_TIMESLICE : msecs_to_jiffies(sched_rr_timeslice); + sched_rr_timeslice = + sysctl_sched_rr_timeslice <= 0 ? RR_TIMESLICE : + msecs_to_jiffies(sysctl_sched_rr_timeslice); } mutex_unlock(&mutex); return ret; -- cgit v1.2.3