linux-kernel - [patch V2 14/15] lockdep: Annotate irq

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Date:   Wed, 18 Mar 2020 21:43:16 +0100
From:   Thomas Gleixner <tglx@...utronix.de>
To:     LKML <linux-kernel@...r.kernel.org>
Cc:     Peter Zijlstra <peterz@...radead.org>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Ingo Molnar <mingo@...nel.org>, Will Deacon <will@...nel.org>,
        "Paul E . McKenney" <paulmck@...nel.org>,
        Joel Fernandes <joel@...lfernandes.org>,
        Steven Rostedt <rostedt@...dmis.org>,
        Randy Dunlap <rdunlap@...radead.org>,
        Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
        Logan Gunthorpe <logang@...tatee.com>,
        Kurt Schwemmer <kurt.schwemmer@...rosemi.com>,
        Bjorn Helgaas <bhelgaas@...gle.com>, linux-pci@...r.kernel.org,
        Felipe Balbi <balbi@...nel.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        linux-usb@...r.kernel.org, Kalle Valo <kvalo@...eaurora.org>,
        "David S. Miller" <davem@...emloft.net>,
        linux-wireless@...r.kernel.org, netdev@...r.kernel.org,
        Oleg Nesterov <oleg@...hat.com>,
        Davidlohr Bueso <dave@...olabs.net>,
        Michael Ellerman <mpe@...erman.id.au>,
        Arnd Bergmann <arnd@...db.de>, linuxppc-dev@...ts.ozlabs.org
Subject: [patch V2 14/15] lockdep: Annotate irq_work

From: Sebastian Andrzej Siewior <bigeasy@...utronix.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@...utronix.de>
Signed-off-by: Thomas Gleixner <tglx@...utronix.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),
 };
 
 /*