This is a note to let you know that I've just added the patch titled
sched/rt: Use container_of() to get root domain in rto_push_irq_work_func()
to the 4.9-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
sched-rt-use-container_of-to-get-root-domain-in-rto_push_irq_work_func.patch
and it can be found in the queue-4.9 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From ad0f1d9d65938aec72a698116cd73a980916895e Mon Sep 17 00:00:00 2001
From: "Steven Rostedt (VMware)" <rostedt@xxxxxxxxxxx>
Date: Tue, 23 Jan 2018 20:45:37 -0500
Subject: sched/rt: Use container_of() to get root domain in rto_push_irq_work_func()
From: Steven Rostedt (VMware) <rostedt@xxxxxxxxxxx>
commit ad0f1d9d65938aec72a698116cd73a980916895e upstream.
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>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
kernel/sched/rt.c | 15 ++++++++-------
1 file changed, 8 insertions(+), 7 deletions(-)
--- a/kernel/sched/rt.c
+++ b/kernel/sched/rt.c
@@ -1895,9 +1895,8 @@ 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;
@@ -1973,7 +1972,7 @@ static void tell_cpu_to_push(struct 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);
@@ -1986,6 +1985,8 @@ static void tell_cpu_to_push(struct 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;
@@ -2001,18 +2002,18 @@ void rto_push_irq_work_func(struct irq_w
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 */
Patches currently in stable-queue which might be from rostedt@xxxxxxxxxxx are
queue-4.9/sched-rt-use-container_of-to-get-root-domain-in-rto_push_irq_work_func.patch
queue-4.9/sched-rt-up-the-root-domain-ref-count-when-passing-it-around-via-ipis.patch