diff options
| author | Sebastian Andrzej Siewior <bigeasy@linutronix.de> | 2017-01-24 15:40:06 +0100 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2017-03-31 09:49:54 +0200 |
| commit | 2bed5987692cb6dc3bf3ce15d8abeb79fdf4ab2a (patch) | |
| tree | d954263c95892561a6079ceabd63de2916c2e7ba /kernel/sched/rt.c | |
| parent | 7a5202190810dde1467718235c1f650fcf57592a (diff) | |
sched/rt: Add a missing rescheduling point
commit 619bd4a71874a8fd78eb6ccf9f272c5e98bcc7b7 upstream.
Since the change in commit:
fd7a4bed1835 ("sched, rt: Convert switched_{from, to}_rt() / prio_changed_rt() to balance callbacks")
... we don't reschedule a task under certain circumstances:
Lets say task-A, SCHED_OTHER, is running on CPU0 (and it may run only on
CPU0) and holds a PI lock. This task is removed from the CPU because it
used up its time slice and another SCHED_OTHER task is running. Task-B on
CPU1 runs at RT priority and asks for the lock owned by task-A. This
results in a priority boost for task-A. Task-B goes to sleep until the
lock has been made available. Task-A is already runnable (but not active),
so it receives no wake up.
The reality now is that task-A gets on the CPU once the scheduler decides
to remove the current task despite the fact that a high priority task is
enqueued and waiting. This may take a long time.
The desired behaviour is that CPU0 immediately reschedules after the
priority boost which made task-A the task with the lowest priority.
Suggested-by: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Thomas Gleixner <tglx@linutronix.de>
Fixes: fd7a4bed1835 ("sched, rt: Convert switched_{from, to}_rt() prio_changed_rt() to balance callbacks")
Link: http://lkml.kernel.org/r/20170124144006.29821-1-bigeasy@linutronix.de
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'kernel/sched/rt.c')
| -rw-r--r-- | kernel/sched/rt.c | 3 |
1 files changed, 1 insertions, 2 deletions
diff --git a/kernel/sched/rt.c b/kernel/sched/rt.c index 8ec86abe0ea1..78ae5c1d9412 100644 --- a/kernel/sched/rt.c +++ b/kernel/sched/rt.c @@ -2136,10 +2136,9 @@ static void switched_to_rt(struct rq *rq, struct task_struct *p) #ifdef CONFIG_SMP if (p->nr_cpus_allowed > 1 && rq->rt.overloaded) queue_push_tasks(rq); -#else +#endif /* CONFIG_SMP */ if (p->prio < rq->curr->prio) resched_curr(rq); -#endif /* CONFIG_SMP */ } } |