From 364f56653708ba8bcdefd4f0da2a42904baa8eeb Mon Sep 17 00:00:00 2001 From: "Steven Rostedt (VMware)" Date: Tue, 23 Jan 2018 20:45:38 -0500 Subject: sched/rt: Up the root domain ref count when passing it around via IPIs When issuing an IPI RT push, where an IPI is sent to each CPU that has more than one RT task scheduled on it, it references the root domain's rto_mask, that contains all the CPUs within the root domain that has more than one RT task in the runable state. The problem is, after the IPIs are initiated, the rq->lock is released. This means that the root domain that is associated to the run queue could be freed while the IPIs are going around. Add a sched_get_rd() and a sched_put_rd() that will increment and decrement the root domain's ref count respectively. This way when initiating the IPIs, the scheduler will up the root domain's ref count before releasing the rq->lock, ensuring that the root domain does not go away until the IPI round is complete. Reported-by: Pavan Kondeti Signed-off-by: Steven Rostedt (VMware) Signed-off-by: Peter Zijlstra (Intel) Cc: Andrew Morton Cc: Linus Torvalds Cc: Mike Galbraith Cc: Peter Zijlstra Cc: Thomas Gleixner Fixes: 4bdced5c9a292 ("sched/rt: Simplify the IPI based RT balancing logic") Link: http://lkml.kernel.org/r/CAEU1=PkiHO35Dzna8EQqNSKW1fr1y1zRQ5y66X117MG06sQtNA@mail.gmail.com Signed-off-by: Ingo Molnar --- kernel/sched/rt.c | 9 +++++++-- 1 file changed, 7 insertions(+), 2 deletions(-) (limited to 'kernel/sched/rt.c') diff --git a/kernel/sched/rt.c b/kernel/sched/rt.c index 2fb627d062e5..89a086ed2b16 100644 --- a/kernel/sched/rt.c +++ b/kernel/sched/rt.c @@ -1990,8 +1990,11 @@ static void tell_cpu_to_push(struct rq *rq) rto_start_unlock(&rq->rd->rto_loop_start); - if (cpu >= 0) + if (cpu >= 0) { + /* Make sure the rd does not get freed while pushing */ + sched_get_rd(rq->rd); irq_work_queue_on(&rq->rd->rto_push_work, cpu); + } } /* Called from hardirq context */ @@ -2021,8 +2024,10 @@ void rto_push_irq_work_func(struct irq_work *work) raw_spin_unlock(&rd->rto_lock); - if (cpu < 0) + if (cpu < 0) { + sched_put_rd(rd); return; + } /* Try the next RT overloaded CPU */ irq_work_queue_on(&rd->rto_push_work, cpu); -- cgit v1.2.3