[patch V3 19/20] lockdep: Annotate irq_work

Thomas Gleixner
2020-03-21T11:35:45Z

From: Sebastian Andrzej Siewior <bigeasy@linutronix.de>

Mark irq_work items with IRQ_WORK_HARD_IRQ which should be invoked in
hardirq context even on PREEMPT_RT. IRQ_WORK without this flag will be
invoked in softirq context on PREEMPT_RT.

Set ->irq_config to 1 for the IRQ_WORK items which are invoked in softirq
context so lockdep knows that these can safely acquire a spinlock_t.

Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
---
include/linux/irq_work.h | 2 ++
include/linux/irqflags.h | 13 +++++++++++++
kernel/irq_work.c | 2 ++
kernel/rcu/tree.c | 1 +
kernel/time/tick-sched.c | 1 +
5 files changed, 19 insertions(+)

--- a/include/linux/irq_work.h
+++ b/include/linux/irq_work.h
@@ -18,6 +18,8 @@

/* Doesn't want IPI, wait for tick: */
#define IRQ_WORK_LAZY BIT(2)
+/* Run hard IRQ context, even on RT */
+#define IRQ_WORK_HARD_IRQ BIT(3)

#define IRQ_WORK_CLAIMED (IRQ_WORK_PENDING | IRQ_WORK_BUSY)

--- a/include/linux/irqflags.h
+++ b/include/linux/irqflags.h
@@ -69,6 +69,17 @@ do { \
current->irq_config = 0; \
} while (0)

+# define lockdep_irq_work_enter(__work) \
+ do { \
+ if (!(atomic_read(&__work->flags) & IRQ_WORK_HARD_IRQ))\
+ current->irq_config = 1; \
+ } while (0)
+# define lockdep_irq_work_exit(__work) \
+ do { \
+ if (!(atomic_read(&__work->flags) & IRQ_WORK_HARD_IRQ))\
+ current->irq_config = 0; \
+ } while (0)
+
#else
# define trace_hardirqs_on() do { } while (0)
# define trace_hardirqs_off() do { } while (0)
@@ -83,6 +94,8 @@ do { \
# define lockdep_softirq_exit() do { } while (0)
# define lockdep_hrtimer_enter(__hrtimer) do { } while (0)
# define lockdep_hrtimer_exit(__hrtimer) do { } while (0)
+# define lockdep_irq_work_enter(__work) do { } while (0)
+# define lockdep_irq_work_exit(__work) do { } while (0)
#endif

#if defined(CONFIG_IRQSOFF_TRACER) || \
--- a/kernel/irq_work.c
+++ b/kernel/irq_work.c
@@ -153,7 +153,9 @@ static void irq_work_run_list(struct lli
*/
flags = atomic_fetch_andnot(IRQ_WORK_PENDING, &work->flags);

+ lockdep_irq_work_enter(work);
work->func(work);
+ lockdep_irq_work_exit(work);
/*
* Clear the BUSY bit and return to the free state if
* no-one else claimed it meanwhile.
--- a/kernel/rcu/tree.c
+++ b/kernel/rcu/tree.c
@@ -1113,6 +1113,7 @@ static int rcu_implicit_dynticks_qs(stru
!rdp->rcu_iw_pending && rdp->rcu_iw_gp_seq != rnp->gp_seq &&
(rnp->ffmask & rdp->grpmask)) {
init_irq_work(&rdp->rcu_iw, rcu_iw_handler);
+ atomic_set(&rdp->rcu_iw.flags, IRQ_WORK_HARD_IRQ);
rdp->rcu_iw_pending = true;
rdp->rcu_iw_gp_seq = rnp->gp_seq;
irq_work_queue_on(&rdp->rcu_iw, rdp->cpu);
--- a/kernel/time/tick-sched.c
+++ b/kernel/time/tick-sched.c
@@ -245,6 +245,7 @@ static void nohz_full_kick_func(struct i

static DEFINE_PER_CPU(struct irq_work, nohz_full_kick_work) = {
.func = nohz_full_kick_func,
+ .flags = ATOMIC_INIT(IRQ_WORK_HARD_IRQ),
};

/*