I see this was just applied to Linus's tree. It probably should be tagged for stable as well. -- Steve On Tue, 6 Feb 2018 03:54:16 -0800 "tip-bot for Steven Rostedt (VMware)" <tipbot@xxxxxxxxx> wrote: > Commit-ID: ad0f1d9d65938aec72a698116cd73a980916895e > Gitweb: https://git.kernel.org/tip/ad0f1d9d65938aec72a698116cd73a980916895e > Author: Steven Rostedt (VMware) <rostedt@xxxxxxxxxxx> > AuthorDate: Tue, 23 Jan 2018 20:45:37 -0500 > Committer: Ingo Molnar <mingo@xxxxxxxxxx> > CommitDate: Tue, 6 Feb 2018 10:20:33 +0100 > > sched/rt: Use container_of() to get root domain in rto_push_irq_work_func() > > When the rto_push_irq_work_func() is called, it looks at the RT overloaded > bitmask in the root domain via the runqueue (rq->rd). The problem is that > during CPU up and down, nothing here stops rq->rd from changing between > taking the rq->rd->rto_lock and releasing it. That means the lock that is > released is not the same lock that was taken. > > Instead of using this_rq()->rd to get the root domain, as the irq work is > part of the root domain, we can simply get the root domain from the irq work > that is passed to the routine: > > container_of(work, struct root_domain, rto_push_work) > > This keeps the root domain consistent. > > Reported-by: Pavan Kondeti <pkondeti@xxxxxxxxxxxxxx> > Signed-off-by: Steven Rostedt (VMware) <rostedt@xxxxxxxxxxx> > Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx> > Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> > Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx> > Cc: Mike Galbraith <efault@xxxxxx> > Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx> > Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx> > Fixes: 4bdced5c9a292 ("sched/rt: Simplify the IPI based RT balancing logic") > Link: http://lkml.kernel.org/r/CAEU1=PkiHO35Dzna8EQqNSKW1fr1y1zRQ5y66X117MG06sQtNA@xxxxxxxxxxxxxx > Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx> > --- > kernel/sched/rt.c | 15 ++++++++------- > 1 file changed, 8 insertions(+), 7 deletions(-) > > diff --git a/kernel/sched/rt.c b/kernel/sched/rt.c > index 862a513..2fb627d 100644 > --- a/kernel/sched/rt.c > +++ b/kernel/sched/rt.c > @@ -1907,9 +1907,8 @@ static void push_rt_tasks(struct rq *rq) > * the rt_loop_next will cause the iterator to perform another scan. > * > */ > -static int rto_next_cpu(struct rq *rq) > +static int rto_next_cpu(struct root_domain *rd) > { > - struct root_domain *rd = rq->rd; > int next; > int cpu; > > @@ -1985,7 +1984,7 @@ static void tell_cpu_to_push(struct rq *rq) > * Otherwise it is finishing up and an ipi needs to be sent. > */ > if (rq->rd->rto_cpu < 0) > - cpu = rto_next_cpu(rq); > + cpu = rto_next_cpu(rq->rd); > > raw_spin_unlock(&rq->rd->rto_lock); > > @@ -1998,6 +1997,8 @@ static void tell_cpu_to_push(struct rq *rq) > /* Called from hardirq context */ > void rto_push_irq_work_func(struct irq_work *work) > { > + struct root_domain *rd = > + container_of(work, struct root_domain, rto_push_work); > struct rq *rq; > int cpu; > > @@ -2013,18 +2014,18 @@ void rto_push_irq_work_func(struct irq_work *work) > raw_spin_unlock(&rq->lock); > } > > - raw_spin_lock(&rq->rd->rto_lock); > + raw_spin_lock(&rd->rto_lock); > > /* Pass the IPI to the next rt overloaded queue */ > - cpu = rto_next_cpu(rq); > + cpu = rto_next_cpu(rd); > > - raw_spin_unlock(&rq->rd->rto_lock); > + raw_spin_unlock(&rd->rto_lock); > > if (cpu < 0) > return; > > /* Try the next RT overloaded CPU */ > - irq_work_queue_on(&rq->rd->rto_push_work, cpu); > + irq_work_queue_on(&rd->rto_push_work, cpu); > } > #endif /* HAVE_RT_PUSH_IPI */ >