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Subject[PATCH RT 2/3] irq_work: Fix checking of IRQ_WORK_LAZY flag set on non PREEMPT_RT
4.19.106-rt46-rc1 stable review patch.
If anyone has any objections, please let me know.

------------------

From: "Steven Rostedt (VMware)" <rostedt@goodmis.org>

When CONFIG_PREEMPT_RT_FULL is not set, some of the checks for using
lazy_list are not properly made as the IRQ_WORK_LAZY is not checked. There's
two locations that need this update, so a use_lazy_list() helper function is
added and used in both locations.

Link: https://lore.kernel.org/r/20200321230028.GA22058@duo.ucw.cz
Reported-by: Pavel Machek <pavel@denx.de>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
---
kernel/irq_work.c | 15 ++++++++-------
1 file changed, 8 insertions(+), 7 deletions(-)

diff --git a/kernel/irq_work.c b/kernel/irq_work.c
index 2940622da5b3..b6d9d35941ac 100644
--- a/kernel/irq_work.c
+++ b/kernel/irq_work.c
@@ -70,6 +70,12 @@ static void __irq_work_queue_local(struct irq_work *work, struct llist_head *lis
arch_irq_work_raise();
}

+static inline bool use_lazy_list(struct irq_work *work)
+{
+ return (IS_ENABLED(CONFIG_PREEMPT_RT_FULL) && !(work->flags & IRQ_WORK_HARD_IRQ))
+ || (work->flags & IRQ_WORK_LAZY);
+}
+
/* Enqueue the irq work @work on the current CPU */
bool irq_work_queue(struct irq_work *work)
{
@@ -81,11 +87,10 @@ bool irq_work_queue(struct irq_work *work)

/* Queue the entry and raise the IPI if needed. */
preempt_disable();
- if (IS_ENABLED(CONFIG_PREEMPT_RT_FULL) && !(work->flags & IRQ_WORK_HARD_IRQ))
+ if (use_lazy_list(work))
list = this_cpu_ptr(&lazy_list);
else
list = this_cpu_ptr(&raised_list);
-
__irq_work_queue_local(work, list);
preempt_enable();

@@ -106,7 +111,6 @@ bool irq_work_queue_on(struct irq_work *work, int cpu)

#else /* CONFIG_SMP: */
struct llist_head *list;
- bool lazy_work, realtime = IS_ENABLED(CONFIG_PREEMPT_RT_FULL);

/* All work should have been flushed before going offline */
WARN_ON_ONCE(cpu_is_offline(cpu));
@@ -116,10 +120,7 @@ bool irq_work_queue_on(struct irq_work *work, int cpu)
return false;

preempt_disable();
-
- lazy_work = work->flags & IRQ_WORK_LAZY;
-
- if (lazy_work || (realtime && !(work->flags & IRQ_WORK_HARD_IRQ)))
+ if (use_lazy_list(work))
list = &per_cpu(lazy_list, cpu);
else
list = &per_cpu(raised_list, cpu);
--
2.25.1

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