diff options
author | Peter Zijlstra <peterz@infradead.org> | 2015-06-11 14:46:39 +0200 |
---|---|---|
committer | Ben Hutchings <ben@decadent.org.uk> | 2016-06-15 21:29:35 +0100 |
commit | 070654cc0f0defaf236f986014591dcc87ff9f87 (patch) | |
tree | 01c5207f8d81667de184fb340aecb69f2143d0d6 /kernel | |
parent | 0589c0247b67e62208ecfbc7ceea4502e5b780cb (diff) |
sched: Allow balance callbacks for check_class_changed()
commit 4c9a4bc89a9cca8128bce67d6bc8870d6b7ee0b2 upstream.
In order to remove dropping rq->lock from the
switched_{to,from}()/prio_changed() sched_class methods, run the
balance callbacks after it.
We need to remove dropping rq->lock because its buggy,
suppose using sched_setattr()/sched_setscheduler() to change a running
task from FIFO to OTHER.
By the time we get to switched_from_rt() the task is already enqueued
on the cfs runqueues. If switched_from_rt() does pull_rt_task() and
drops rq->lock, load-balancing can come in and move our task @p to
another rq.
The subsequent switched_to_fair() still assumes @p is on @rq and bad
things will happen.
By using balance callbacks we delay the load-balancing operations
{rt,dl}x{push,pull} until we've done all the important work and the
task is fully set up.
Furthermore, the balance callbacks do not know about @p, therefore
they cannot get confused like this.
Reported-by: Mike Galbraith <umgwanakikbuti@gmail.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: ktkhai@parallels.com
Cc: rostedt@goodmis.org
Cc: juri.lelli@gmail.com
Cc: pang.xunlei@linaro.org
Cc: oleg@redhat.com
Cc: wanpeng.li@linux.intel.com
Link: http://lkml.kernel.org/r/20150611124742.615343911@infradead.org
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
[Conflicts: kernel/sched/core.c]
Signed-off-by: Byungchul Park <byungchul.park@lge.com>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
Diffstat (limited to 'kernel')
-rw-r--r-- | kernel/sched/core.c | 24 |
1 files changed, 23 insertions, 1 deletions
diff --git a/kernel/sched/core.c b/kernel/sched/core.c index d8979489da08..8cbf68e6985d 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -999,6 +999,13 @@ inline int task_curr(const struct task_struct *p) return cpu_curr(task_cpu(p)) == p; } +/* + * switched_from, switched_to and prio_changed must _NOT_ drop rq->lock, + * use the balance_callback list if you want balancing. + * + * this means any call to check_class_changed() must be followed by a call to + * balance_callback(). + */ static inline void check_class_changed(struct rq *rq, struct task_struct *p, const struct sched_class *prev_class, int oldprio) @@ -1500,8 +1507,12 @@ ttwu_do_wakeup(struct rq *rq, struct task_struct *p, int wake_flags) p->state = TASK_RUNNING; #ifdef CONFIG_SMP - if (p->sched_class->task_woken) + if (p->sched_class->task_woken) { + /* + * XXX can drop rq->lock; most likely ok. + */ p->sched_class->task_woken(rq, p); + } if (rq->idle_stamp) { u64 delta = rq_clock(rq) - rq->idle_stamp; @@ -3052,7 +3063,11 @@ void rt_mutex_setprio(struct task_struct *p, int prio) check_class_changed(rq, p, prev_class, oldprio); out_unlock: + preempt_disable(); /* avoid rq from going away on us */ __task_rq_unlock(rq); + + balance_callback(rq); + preempt_enable(); } #endif @@ -3575,10 +3590,17 @@ change: } check_class_changed(rq, p, prev_class, oldprio); + preempt_disable(); /* avoid rq from going away on us */ task_rq_unlock(rq, p, &flags); rt_mutex_adjust_pi(p); + /* + * Run balance callbacks after we've adjusted the PI chain. + */ + balance_callback(rq); + preempt_enable(); + return 0; } |